Fresh Fizz Posted February 20, 2008 Report Share Posted February 20, 2008 There seems to be a lot of work right now into alternative grounding schemes. Has anyone worked out if this is even an issue (at least for there system)? If all this work is based on hunches and guesswork, then not only might it be pointless, it might even cause more problems by making potential solutions to real problems more difficult to achieve. Yes, you're right. I'm only wild guessing. But everybody who is working on this sustainer project has some problem with fizz or grunge. It's the desire to make some progress that makes people come up with all sorts of hypotheses. It shouldn't be too difficult to find this out through experimentation. I don't think this is true. You could experience that an alternative grounding system didn't improve the performance. But what if more conditions have to be met before there is an improvement? It's better to think loud. Maybe some can make good use of it. Or eventually prove I'm wrong. Thanks for suggestions. Fresh Fizz, as I looked your schematic, is there any buffer between guitar and sustainer? My current setup doesn't include any dedicated buffer, only an eq. As those have common ground, turning sustainer's volume down turns also guitars's volume down. Strange that I haven't noticed it before.. Next I have to make some decent splitter/buffer, something like Craig Anderton's "spluffer". It uses outdated ic's, so I have to re-draw the schematic. It also uses split power supply, so we'll see what it has to offer. No utopian isotope there is no buffer, my volume pot acts the same as yours. I personally like it this way. By the way it wasn't my intention to draw a complete schematic but only the grounding issues. Fresh Fizz Link to comment Share on other sites More sharing options...
psw Posted February 20, 2008 Author Report Share Posted February 20, 2008 There seems to be a lot of work right now into alternative grounding schemes. Well...I don't know about a lot of work, I have continually asked the question as I have failed to understand a technique for isolating the ground. I am not sure that the resistor suggested here is going to "isolate" anything really as any power surge (on off pop), back voltage (as suggested from a driver coil being out of phase?) or any other distortions that may be entering the signal (if they are) via the ground wire. Has anyone worked out if this is even an issue (at least for there system)? I have noted that all circuit designs have shown a shared signal and driver ground and all experience fizz and other symptoms associated with EMI. Is it not reasonable then to wonder if this wasn't contributing and to seek help in trying to find a way to eliminate it from the equation. If all this work is based on hunches and guesswork, then not only might it be pointless, it might even cause more problems by making potential solutions to real problems more difficult to achieve. It shouldn't be too difficult to find this out through experimentation. Well...no, it shouldn't...if you knew a way of isolating the ground and testing that...but I don't...can you suggest a manner in which I can test the idea? ------------------------------------ @Pete regarding grounding of the driver core. You said that this was a bad idea because you get squeal when you touch the strings to the ungrounded core on your setup. Three things: #1 It is very possible that grounding via the strings is going to cause oscillation due to earth loops (DC offsets?) and suchlike. Creating a proper earth connection in a 'star ground' formation (or some similar acceptable form) should not cause this problem. In order to effectively isolate the ground, I have to maintain strict control of the grounding system in the guitar, I don't think there are any ground loops as everything has to connect via the switch and the controls. SO, possible but not likely, the single switch connection essentially creates a star ground. The fact of very loud squeal if the poles are grounded to the strings is enough to indicate to me that grounding the driver is not going to be a viable option with a direct connection under any circumstances. The fact that apparently electrostatic forces are enough to create a spark indicates that the energy created in the core(s) are significant and probably not something you want to connect directly back into the signal. #2 There is a big difference between having a constant earth connection from power up, and not having one, then making the connection after charge current etc. have had time to build up. Yes...well this could explain the power off pop. In the more recent switching, I am switching the positive power connection and while silent on switching, that off switching is very noticeable and unacceptable as always. I have to switch one or both. Here is a question that may seem dumb, but surprisingly, I have failed to find a reference for it...if I short the battery terminals (+ve to -ve) will this drain the battery or cause other problems...is this a way in which power can safely be "disconnected" over lifting one or other of the power leads? I see your point, though typically on a fender single coil pickup the magnetic pole pieces are not grounded...and so in this case they are not either. Perhaps with a dual coil driver where there are equal and opposite forces at work, groundidng the core does not present too much of a problem. So, the core is not connected before or after. However, you may be right about the secondary pickup coil which is switched in and out of circuit completely (including the ground) causing some problems...however, anyone got any solutions? #3 This is born out by looking at the Sustainiac stealth driver which unsurprisingly has the magnet and core earthed Is it? The core may be connected to something, but who really knows what is going on in the circuit. For instace the fernandes circuit features a transformer...if this to islolate the coil(s)? What about the mammoth caps in the sustainer circuit? We know that there is phase cancellation circuits and possibly D-class amps (also apparently not referenced to ground at their output)...the trio of op-amps in the all-pass filter circuits using instrumentation amps seem to isolate the signal ground also, or so it would seem. Another question for you - this time about the secondary coil business. You've suggested that this coil is improving the response or drive in some way. Well...it is having an "effect". The difference between shorting and even a relatively small load is substantial. It requires far more amplification to achieve the same effect with the leads shorted. However, there is less of a harmonic response (not the harmonic switch) with the pickup coil shorted. An open coil is even more "effective" (as is has this effect) and the LM 386 is possibly too much on even it's lowest gain setting (I have no input volume control but control it from pins 1 and 8) Is this when compared with the driver on the pickups core but with no extra coil, or just when compared with the other ways of wiring the secondary pickup coil ? Well...it is compared to various different configurations of the secondary coil (open, shorted, loaded, diodes, caps...etc) If its the former, then that is very interesting, if its the latter, then it doesn't really mean much at all. Obviously I have made very many stand alone drivers with secondary coils. I have used different pickup types too...a stacked pickup for instance could be expected to have a very different effect with it's dual and opposite secondary coils. Generally, because they aren't typically grounded, I have not had grounded cores. Grounding them has caused massive squeal in the past. The original DIY sustainer was built onto a pickup only after a separate identical version was made and tested. However, with the benefit of hindsight and recent discoveries about the "effect" of secondary coils, this was not really explored. It was found that I needed to short the pickup coil to control squeal and distortion (as did curtisa with his version) but at that time we did not look into loading the coil. It is quite likely that some of the installation problems associated with this were a result of not appreciating the significance of secondary coils. Also of note is that on this guitar, I shorted the middle (presumably rwrp) with the neck pickup having a desirable effect or creating a load of some description. Or...it had a less than desirable effect by having a second secondary coil even closer to the bridge pickup!!! Do you have a pickup to test with that has an easily removable coil ? That would enable you to find out for sure what impact that pickup coil is having (assuming you haven't already done this of course ) Unfortunately, with this coreless design, it is a little tricky to test...unlike previous versions it is not so simple to stick a magnet on to it. If I can find a pickup that is stripped of wire, I may try this. With this particular design, as the secondary coil is a necessary part of the concept, I didn't see the benefit of repeating previous experiments with thin coils...perhaps there is some....hmmmm cheers Col Yes, you're right. I'm only wild guessing. blush.gif But everybody who is working on this sustainer project has some problem with fizz or grunge. It's the desire to make some progress that makes people come up with all sorts of hypotheses. Exactly....we are only assuming that the fizz is purely EMI based until this has been ruled out or otherwise addressed. For sure we can see that the squeal is, and I am sure that some distortion is also EMI based...but all of it? I have yet to find a scheme that addresses the problem with the circuit designs we use that tie the driver coil ground and the signal ground directly... Without such a scheme, how does one experiment. The use of a separate power supply does not seem to be convincing and risks huge earth loops in the mains between the ground in the amplifier and the power supply to the guitar. Either way, with the signal and ground connected anyway...they are still shared and so not separated. Regardless...both of the present experimenters are using non-earthed power supplies it appears! Next I have to make some decent splitter/buffer This is a good idea...something like this is possibly advantageous. I think col's circuit has such a preamp (the signal out of the guitar is buffered and the signal into the amp if I recall). Perhaps a reason for less problems of this nature? On the other hand...fizz has an active buffer/treble booster preamp in the guitar already, so perhaps this is addressing any loading issues. Without a preamp, most if not all power-amps will load the signal and this will be immediately apparent in comparing the sound of the guitar with the device off and on. The sustainer circuit won't produce full power if grossly mismatched in input impedance either. As those have common ground, turning sustainer's volume down turns also guitars's volume down. Strange that I haven't noticed it before.. The splitter preamp may address this problem and is a reason why I am considering it. Also...there is some increased distortion when turning down the guitars volume as doing so results in loading of the pickup (that is how the volume control works, it adds the pot value to the signal, the loading effects can be heard by reduced brightness that may restore with a small bypass cap on the volume control for this very reason. Loading the pickup via the volume control with typical circuits (perhaps not col's?) means adding load to the ground and so effecting the driver, the signal and all other associated parts. This symptom: increased fizz with increased input load to ground, shared with the driver. should alone give cause to question the significance of the shared ground of these components and seek to test this hypothesis...no? Until this grounding hypothesis is ruled out as significant, then it is no more crazy a suggestion than the assumption that all fizz is created by EMI issues. In support of my conjecture for instance, the decreasing of the signal, if the distortion is purely EMI based, should result in less EMI effects as the driver is putting out less EMI...but in fact the above would suggest that the opposite is true. Thanks for the drawing fizz, I need this kind of thing to fully understand what you were suggesting previously...I am not sure that this is going to adequately put to rest the issue however (a resistor is not isolating anything really, but may have an effect;)) pete Link to comment Share on other sites More sharing options...
curtisa Posted February 20, 2008 Report Share Posted February 20, 2008 I have yet to find a scheme that addresses the problem with the circuit designs we use that tie the driver coil ground and the signal ground directly... Without such a scheme, how does one experiment. What's wrong with using a signal transformer to isolate the driver signal? That's the easiest (and only!) way to fully isolate two AC circuit's earths. Link to comment Share on other sites More sharing options...
psw Posted February 20, 2008 Author Report Share Posted February 20, 2008 I have yet to find a scheme that addresses the problem with the circuit designs we use that tie the driver coil ground and the signal ground directly... Without such a scheme, how does one experiment. What's wrong with using a signal transformer to isolate the driver signal? That's the easiest (and only!) way to fully isolate two AC circuit's earths. Ok...will see what I can do in that regard... I did a little tentative research... This is interesting and may have definitions and formulas of interest to some with a more technical and analytical skill, or just to get some new thoughts...signal transformers / auto transformers... However, it would appear that these things will block DC voltages, but not AC. Would not a small decoupling capacitor to separate the signal and driver ground have a similar effect? (ie inserted where fizz has suggested a resistor?). The question though arises that the distortion/fizz is likely to be AC in nature and so will still enter via the shared ground. Some may remember my desire to try BTL amps and D-class systems specifically because they appear not to share directly the ground (so directly anyway) as with our common systems. I even made a dual LM386 amp in BTL for this very reason. In trying BTL setups though, I have had little success compared to the simple LM386 type circuits. Other ideas that come to mind is a balanced signal source...Differential / balanced signal wiki Also...ground loop wiki makes you wonder about the possibility of a phantom loop. As far fetched as this seems, it is entirely possible...so how to avoid...hmmmm The possible problem as I see it is that the driver may be causing some kind of signal back into the circuit and through the ground directly into the guitars output signal. This may be in the form of "fizzy distortion". It may be some capacitance in the coil or as a result of phase discrepancies...I really don't know...it may be induced by eddy currents in the core. It may not even exist (however there is a lot to suggest it does from a lot of contributors and texts). It has been cited as a reason for my persistent "off pop"...a sudden inrush of residual power in the driver coil returning to ground. It is not an unrealistic nor outlandish proposition and one that really needs to be explored, if only to rule it out. Quite how to do that, I am not sure. Clearly isolation transformers (signal transformers) exist for a reason...presumably to address noise problems as I suggest. As another approach...how about an optocoupler...would this not provide some isolation? How would such a thing be implemented, on the signal ground, the driver? I actually have a few of these devices, so I would be willing to do some experimentation if it was thought to be a worthwhile avenue to explore. Another idea I had was perhaps to use a 4066 electronic switch to disconnect the driver when power is off. So, turning on the device would result in the driver coming out of the system and maybe addressing my "pop" issue (which I (and others like R.G. suspect is also related to the issues we are discussing). In thinking along these lines, it could be another means of AGC (although noise could be inherent) where a CV signal is generated to trigger it from the input signal. The idea being, that when the signal reaches a point at which the signal is excessive and so fizz is more apparent, the driver is disconnected till the signal returns to a more reasonable level... Any thoughts on these ideas or the conundrum in general. Any ideas on how the whole ground/noise thing can be tested? pete Link to comment Share on other sites More sharing options...
col Posted February 20, 2008 Report Share Posted February 20, 2008 There seems to be a lot of work right now into alternative grounding schemes. Well...I don't know about a lot of work, I have continually asked the question as I have failed to understand a technique for isolating the ground. I am not sure that the resistor suggested here is going to "isolate" anything really as any power surge (on off pop), back voltage (as suggested from a driver coil being out of phase?) or any other distortions that may be entering the signal (if they are) via the ground wire. The resistor suggestion is whats known as a 'ground lift' it is sometimes used to fix ground loop problems. Has anyone worked out if this is even an issue (at least for there system)? I have noted that all circuit designs have shown a shared signal and driver ground and all experience fizz and other symptoms associated with EMI. Is it not reasonable then to wonder if this wasn't contributing and to seek help in trying to find a way to eliminate it from the equation. It is normal for analog circuitry to share a common earth - anything else is unusual. It doesn't make sense (to me) to spend a lot of time working on a much more complicated an potentially problematic setup unless we're sure that it is causing problems and that there isn't a better way of solving them. Having said that, its up to you guys what you want to spend your resources on If all this work is based on hunches and guesswork, then not only might it be pointless, it might even cause more problems by making potential solutions to real problems more difficult to achieve. It shouldn't be too difficult to find this out through experimentation. Well...no, it shouldn't...if you knew a way of isolating the ground and testing that...but I don't...can you suggest a manner in which I can test the idea? To find out if a shared ground is a significant contributer to the fizz, you don't need to first develop some kind of fancy isolated circuit system. You do need to have a test rig where the pickup your listening to is not electrically connected to the driver or circuit in any way, but thats pretty easy to set up. You just need to feed that driver from a different pickup that is situated a 'safe' distance away from your test rig. As long as everything else is as it should be - distance between driver and 'listening' pickup is correct, positioning of circuit and leads, positioning of (dummy) strings... basically, it should be possible to keep everything the same apart from the circuit connections. There will be no infinite sustain, but you don't need that to hear the 'fizz'. If you do this and the fizz magically vanishes completely, then there is a much better likelyhood that it can be solved using some fancy isolation system - maybe some opto isolators or a small 1:1 transformer. Maybe someone with a scope could probe the shared earth on their setup to see how it looks ? ------------------------------------ Here is a question that may seem dumb, but surprisingly, I have failed to find a reference for it...if I short the battery terminals (+ve to -ve) will this drain the battery or cause other problems...is this a way in which power can safely be "disconnected" over lifting one or other of the power leads? Connecting the terminals of a battery is a BAD idea - at best it will just kill the battery. If you are unlucky it could get very hot, split, burn, explode even ? "Batteries may leak or explode causing personal injury if inserted improperly, disposed of in fire, mixed with other battery types, or short circuited." #3 This is born out by looking at the Sustainiac stealth driver which unsurprisingly has the magnet and core earthed Is it? The core may be connected to something, but who really knows what is going on in the circuit. ... If you showed the photo from the stealth deconstruction on that German forum to anyone with knowledge of electronics, they would tell you immediately that it is an earth connection - it is very obvious. Unfortunately, with this coreless design, it is a little tricky to test...unlike previous versions it is not so simple to stick a magnet on to it. If I can find a pickup that is stripped of wire, I may try this. With this particular design, as the secondary coil is a necessary part of the concept, I didn't see the benefit of repeating previous experiments with thin coils...perhaps there is some....hmmmm For there to be any point, it must be the same make and model - or the differences in the core could be enough to change the response of the driver (significantly!). cheers Col Link to comment Share on other sites More sharing options...
col Posted February 20, 2008 Report Share Posted February 20, 2008 As another approach...how about an optocoupler...would this not provide some isolation? How would such a thing be implemented, on the signal ground, the driver? I actually have a few of these devices, so I would be willing to do some experimentation if it was thought to be a worthwhile avenue to explore. The problem with an optocoupler is that it needs power, so you would need two power sources - one for the sustainer circuit, and one for the pickup side of the optocoupler. A transformer will bring some problems with it - positioning will be important, and it may need to be housed in some sort of enclosure to reduce interactions with the driver. It is also a relatively large component. Anyhow, if you just go and install a transformer, and discover that the fuzz is pretty much as it was, you won't know if it is the same fuzz, or if it removed the old fuzz, and introduced some brand new fuzz that just sounds and behaves like the old fuzz. cheers Col Link to comment Share on other sites More sharing options...
psw Posted February 21, 2008 Author Report Share Posted February 21, 2008 Well col...some valid points...however, no one has tried quite what you describe as far as I know including yourself so the jury remains out as to the whole point. Assuming everything is down to EMI and driver design is wrought with dangers and as so few have taken this project to it's logical conclusion (fitting it to a standard multi pickup guitar) a lot of what I am doing is relevant to anyone who would wish to do so. I take your point though...if I were to add another pickup purely to provide the signal completely separate from the guitars signal to the circuit then I would achieve isolation. I will try this ASAP...I assume no one else has?! I did try this in very early experiments of course, and in discussions around the eBow where it was conjectured that the eBows all inclusive driver, pickup and circuit enabled it to work as close as it does to the pickups without ill effect.... I will try again! Meanwhile... The problem with an optocoupler is that it needs power, so you would need two power sources - one for the sustainer circuit, and one for the pickup side of the optocoupler. ummm...it couldn't share the same power supply? An interesting source on ground lifting there...included is this... Ground lift is quite effective in balanced audio connections, but is much less useful in unbalanced connections, which is the connection type used in almost all consumer audio equipments. You might try this ground lift scheme with this connection type, but the results would be much worse. Even when you can limit the shield connector current to values which do not cause problems, there is still the ground potential difference between equipments which gets amplified (and you get still some 50 Hz noise). Even ground potential differerences much lower than 1 mV can cause serious noise problems with unbalanced circuits. If you have unblanced connections, I would advice you to use audio isolation transformer instead of ground lift when you are solving problems with nonbalanced audio connections. So...as I was saying...not entirely convinced that with an unbalanced signal and driver that the resistor or the idea of a cap (that I suggested) is going to be effective or not introduce more problems....worth a try though, but hardly conclusive... Anyhow, if you just go and install a transformer, and discover that the fuzz is pretty much as it was, you won't know if it is the same fuzz, or if it removed the old fuzz, and introduced some brand new fuzz that just sounds and behaves like the old fuzz. Quite right! It is normal for analog circuitry to share a common earth - anything else is unusual. That is right, but this is not some kind of straight forward signal processor effect box kind of thing, it has a very unusual set of problems and symptoms that require unusual remedies. Look at the extent people go to to make "better" drivers with exactly the same symptoms as very basic models despite best intentions, theories and so called common sense. It doesn't make sense (to me) to spend a lot of time working on a much more complicated an potentially problematic setup unless we're sure that it is causing problems and that there isn't a better way of solving them. Having said that, its up to you guys what you want to spend your resources on smile.gif Well...I think it doesn't make sense to ignore a perfectly reasonable possibility and spend untold resources perfecting things to address an equally percieved problem. Also, it has been asked why I don't explore various other sides of the project or propositions and I thought it was clear that I felt that as long as a working device can not fully function without pops or fizz or in a practical way, then refining something with these problems is pointless and a waste of "resources". I will put full resources on improving "performance" and new circuit designs when the basic idea is fully functional, not just producing good infinite sustain, but doing so without distortions or pops and in a real playing instrument...not something simply tacked together for an experiment! You do need to have a test rig where the pickup your listening to is not electrically connected to the driver or circuit in any way, but thats pretty easy to set up. I will do this shortly, but it is telling, I assume that you haven't done this yourself. You may be right and it has no relevance...but I think enough points out that some detrimental effect is likely from this shared ground connection and you seem to be running on some kind of indignant faith without proving at all that it is not a factor, suggesting that people are "wasting resources" in even engaging in the conversation about it. Where exactly should my resources go then, I have made any number of drivers and designs, circuits (most sharing grounds) and test rigs including whole guitars...what would you suggest I do...what are you doing to address these concerns that you too share? I think that is insulting, despite the smiley not only to me but to people who may engage in the discussion and does nothing to help address these problems... As long as everything else is as it should be - distance between driver and 'listening' pickup is correct, positioning of circuit and leads, positioning of (dummy) strings... basically, it should be possible to keep everything the same apart from the circuit connections. There will be no infinite sustain, but you don't need that to hear the 'fizz'. I am not sure here what you mean...are you suggesting effectively two guitars, not even sharing the same strings? Well, you may be right that this may be the only way to test it...however not so easy I would suggest! Also, it is hardly doing the same thing and is reminiscent of the early experiments I described recently where I fed the driver with signals generated on a computer. I could set up another pickup and listen on this while the existing pickup and driver excite the strings but setting up and accurately tuning two guitars is a lot to ask...I would need two amps of course to avoid sharing the grounds in there too... Fizz only occurs when the device is operating at a level that produces infinite sustain. So I am a little confused...but I may even, on reflection, be able to power the sustainer circuit from a perfectly tuned second guitar. Remember I even tried to make my own ebow...some of this motivation was not to build one, but to understand a little more about these phenomena. Connecting the terminals of a battery is a BAD idea - at best it will just kill the battery. If you are unlucky it could get very hot, split, burn, explode even ? Thanks...just as I thought... #3 This is born out by looking at the Sustainiac stealth driver which unsurprisingly has the magnet and core earthed Is it? The core may be connected to something, but who really knows what is going on in the circuit. ... If you showed the photo from the stealth deconstruction on that German forum to anyone with knowledge of electronics, they would tell you immediately that it is an earth connection - it is very obvious. I don't recall they ever specified that the core was grounded... certainly it had a copper shield around the coil that was grounded (like most of my pickups) but then it is used as a pickup in non-sustainer mode and that would be advantageous. Even if it is grounded, it may the signal may well be isolated from any induced noise that can occur in any transformer or electromagnetic device. There is no evidence to suggest that this is a fact and I observed no direct ground connection. It is not always common in guitar pickups to ground the magnets (especially with fender types) and ceramics are non conductive so that is a little difficult to do too. In a pickup it probably is advantageous, but if any reverse phasing is used, this connection must be severed as it would become "hot...would it not? I have not seen any evidence that the sustainiac or any other driver core is grounded conventionally, yet there is every reason to assume that the action of the coil on the core produces eddy currents and probably electrostatic and capacitive forces that could create unwanted artifacts, maybe in the form of a fizzy distortion in the shared ground, or transmitted into the grounded strings. Being "obvious" doesn't cut it as a convincing argument for a fact. The fact is that I have had very knowledgeable people look at this project and not come up with answers, certainly no one suggested that, hey you, ground that core! Mostly, a lot of people jump to the wrong conclusions typically treating it as a simple audio preamp or something and miss the uniqueness of this particular devices problems. I have had any number of people suggest "pop" solutions typical in stompbox projects, but they do not work in this device. R.G. Keen went so far as to suggest it was a coil backlash....fizz recently pointed out that relays are often fitted with diodes to avoid the same effect...and that it was unlikely that there would be a solution. Obviously, sustainiac et al found one. Testing my driver without the secondary coil is not a real answer...it is worth the experiment, but the big lump of copper (regardless of it being in the form of a coil) wrapped around the core is going to have an effect. This effect can be heard. The fact that it is in a coil and obviously generating some linked forces and that adjusting this with loads produces some changes in resonances, proves that it has an effect. It is not inconceivable that these forces could be used to aid in the operation of the driver...it is likely that uncontrolled (not shorted or loaded) the effect is unpredictable. It may be that it's presence is detrimental to performance, but it is hard to be sure. I am not advocating secondary coils, but I am advocating the idea of a design that can operate as both a passive pickup and as a driver on practical grounds. If anyone has an ebow, perhaps they could report on any fizzy like effects that may be present when using that device. Are the distortions produced purely from overdriving the strings, or are they a result of the pickup, picking up the ebows signal? Other than this avenue of exploration into the issues of distortions and switching noise, I fail to see a more productive direction to direct my resources...I wish I could. I don't want an isolation transformer...anymore than fernandes do! I have made my fair share of stand alone drivers too. Sure, I am working this design to death, but I won't get anywhere swapping and changing all the time and still encountering the same symptoms. If you recall the last driver I committed to was a dual coil rail design propositioned as a very encouraging concept. I built it with a lot of care and I made others including a side driver to test ideas. But, while these problems of fizz and such are continually being put forward and switch noise is still an issue, then regardless of the driver design these "problems" need to be addressed. I have exhausted my ideas to a great extent (though there is no limit to the possible approaches) yet these things remain to plague the device. It is for that reason I seeking to look at some of the other common factors within the systems, and that shared ground of signal and driver is a glaring example and really I don't feel that it is a waste of resources to consider it, engage in a discussion or even to experiment at my own expense for lack of any other ideas, obvious or not, that people may be keeping for themselves. I would like to point out that I am no way underestimating the EMI issue, it is a major factor, but I suspect that there are other factors too. For instance...since you have a working model with a grounded core (mine won't tolerate grounding)...then perhaps col you could consider lifting this connection and reporting on the effect or otherwise that this small alteration may have! It could do nothing, it could make it worse, it could make it better. Did you ground it because it was "obvious" or because it cured some ill effect? ------------ Another factor that may influence things is clean headroom. I intend to try a more powerful amplifier in the near future to see if a cleaner signal influence these effects. From the way fizz is increased in proportion to the less drive with the battery running flat on my circuit, perhaps this is an area that warrants exploration too! pete Link to comment Share on other sites More sharing options...
col Posted February 21, 2008 Report Share Posted February 21, 2008 You may be right and it has no relevance...but I think enough points out that some detrimental effect is likely from this shared ground connection and you seem to be running on some kind of indignant faith without proving at all that it is not a factor, suggesting that people are "wasting resources" in even engaging in the conversation about it. I've never suggested that I think a shared ground cannot be a source of fizz - it is just as likely to be the cause as any other factor - the point I've been trying to make is that it isn't sensible to throw lots of effort into 'solving it' when its just as likely to not be a problem. Where exactly should my resources go then, I have made any number of drivers and designs, circuits (most sharing grounds) and test rigs including whole guitars...what would you suggest I do...what are you doing to address these concerns that you too share? I think that is insulting, despite the smiley not only to me but to people who may engage in the discussion and does nothing to help address these problems... Hang on there, whoooah... All I'm saying is that I would want to be sure there is a problem with the existing earth setup before trying to fix it , but also that it's not up to me to tell anyone else what they should be doing. I am not sure here what you mean...are you suggesting effectively two guitars, not even sharing the same strings? Well, you may be right that this may be the only way to test it...however not so easy I would suggest! Also, it is hardly doing the same thing and is reminiscent of the early experiments I described recently where I fed the driver with signals generated on a computer. I could set up another pickup and listen on this while the existing pickup and driver excite the strings but setting up and accurately tuning two guitars is a lot to ask No, just one guitar, the other set of strings can just be stretched over a plank of wood as long as they have the same spacing - I'm not sure if tension is important - they're only there to provide the possible electromagnetic 'fizz' bridge between driver and pickup. No need for two amps - just a single headphone amp - and that would not have a guitar note, rather, it would have just the fuzz - or no fuzz if one has removed the fuzz causing aspect of the system. What you suggest - using a signal generator to feed the driver might work better, but it would need to have the correct harmonic spectrum just to be sure. The main thing is that the pickup you listen to will only have the fizz sound - no 'note'. and its important to have the guitar that is the signal source (unless a PC or signal generator is used) as physically far away as possible to minimize its interactions with the test rig. You're right that I've not built this yet, but I intend to ASAP - I only thought it through a few days ago, and I've been busy in the daytime and can't use noisy tools in the evening which is when I have spare time, so I tend to do more 'theoretical' research. Fizz only occurs when the device is operating at a level that produces infinite sustain. So I am a little confused...but I may even, on reflection, be able to power the sustainer circuit from a perfectly tuned second guitar. Remember I even tried to make my own ebow...some of this motivation was not to build one, but to understand a little more about these phenomena. For this idea, tuning is only necessary in the source guitar - hence the plank with strings attached for the test rig - the idea is that we are not making a sustainer, we are making a fizz explorer. Other than this avenue of exploration into the issues of distortions and switching noise, I fail to see a more productive direction to direct my resources...I wish I could. ................... But, while these problems of fizz and such are continually being put forward and switch noise is still an issue, then regardless of the driver design these "problems" need to be addressed. I have exhausted my ideas to a great extent (though there is no limit to the possible approaches) yet these things remain to plague the device. Exactly the reason I'm advocating trying to find what the causes of the problems are by isolating the possible causes. It is important to come up with ways of working out what's causing these problems. These methods don't have to be theoretical. The test rig I have proposed may or may not be useful, but I'm sure that there are other better ways that I've not considered. If we all thought more about finding what the actual causes of the problems are rather than jumping to conclusions (I'm as guilty as the next guy of this one) - we would be on the right track. ------------------------------ As far as your switch noise, part of the trouble seems to be with definition - are we talking about normal small scratchy clicks like you might get switching a stomp box - or are we talking aobut the big 'thwump' that you get with som amps when you turn them off ? If its the former, then the usual tricks for dealing with noisy switches should work. If its the latter (I guess so?) then the only solutions I've come across use some sort of delayed switching circuit. One idea is that when you switch off, it first disconnects the output from the guitars output, then after a short time, it removes power from the sustainer circuit. So the thwump still happens, but you don't get to hear it. The other is like a slow automatic 'dimmer' switch. The thwump is (suposedly) caused by a voltage spike from the driver. When you instantly remove the current from a fully charged inductor the field collapses and results in a voltage spike. If you can reduce the current to off state in a more controlled way, this should prevent the voltage spike and therefor the thwump. I don't have any example circuits - the only ones I saw were pretty complex. cheers Col Link to comment Share on other sites More sharing options...
psw Posted February 21, 2008 Author Report Share Posted February 21, 2008 I've never suggested that I think a shared ground cannot be a source of fizz - it is just as likely to be the cause as any other factor - the point I've been trying to make is that it isn't sensible to throw lots of effort into 'solving it' when its just as likely to not be a problem. Fine...but if it is a problem or a contributor to problems that appear to more or less universal across platforms, then someone should address these concerns. I first want to know if it is a source of problems (even though I suspect it may be) and to then "solve it"...unfortunately, "solving it" maybe the only way to conclusively prove the point. I think something can be done with my guitar and another pickup that is connected to the amp...at least it is a place to start, but not conclusive. All I'm saying is that I would want to be sure there is a problem with the existing earth setup before trying to fix it , but also that it's not up to me to tell anyone else what they should be doing. As above. For lack of any other thing to attempt and the only obvious similarity across platforms, this seems the obvious thing to address if only to rule it out. ...just one guitar, the other set of strings can just be stretched over a plank of wood as long as they have the same spacing - I'm not sure if tension is important - they're only there to provide the possible electromagnetic 'fizz' bridge between driver and pickup. Still not sure if I follow you, but I will see what I can do when I have some time. If its the latter (I guess so?) then the only solutions I've come across use some sort of delayed switching circuit. One idea is that when you switch off, it first disconnects the output from the guitars output, then after a short time, it removes power from the sustainer circuit. So the thwump still happens, but you don't get to hear it. The other is like a slow automatic 'dimmer' switch. The thwump is (suposedly) caused by a voltage spike from the driver. When you instantly remove the current from a fully charged inductor the field collapses and results in a voltage spike. If you can reduce the current to off state in a more controlled way, this should prevent the voltage spike and therefor the thwump. It varies...sometimes it occurs on switch off as a thump, very occasionally it is silent when the thing is actually sustaining. Yes, consensus is that it is a backlash from the driver. Hence the idea of a 4066 to disconnect the driver when the power is turned off. These are normally open so, on switch on, the driver would be connected with the application of power to the circuit, on switch off, it would be disconnected...however a time delay so that this happens first may be a problem. Another problem that may only effect me is that the secondary coil is reconnected on switch off and there may be some kind of voltage spike from that. I suspect that a dual coil driver and or pickup would have less of a problem in this regard. Another possibility is that I use a 100uF power smoothing cap between the +ve and -ve terminals (as is typical), perhaps the circuit remains on momentarily when this discharges when the battery is disconnected...or it's discharge itself is a source of thump! On the 4066 idea...there are 4 spst switches normally open in this device, perhaps I should use two for the driver and two for the signal input of the circuit so it is disconnected on both ends with the disconnection of power...does that sound like a reasonable idea? When switching with the negative (combined with the grounded signal and so maximizing switching power), I think that is when I get a slight click switch on and a varying degree of twump on turn off, perhaps a little less than my present positive switched scheme. I wouldn't at all be surprised if a large cap is not used in the Sustainaic circuit to suppress switch noise. Of course, with a 4pdt toggle switch, I am starved for choice...the idea that these things may not be so reliable came to me when I used a toggle as a selector...here I got a click completely in passive mode...a cheap three or five way blade switch does not have that effect. Some have suggested that FET switching would allow silent switching and to be "on" even with no power. Someone suggested recently that it would solve all the problems, but I suspect that he was thinking with the "obvious" stompbox philosophy and not appreciating other factors associated with noise (as discussed above) unique to this project. Can anyone verify that FET's will conduct even without power? If so, perhaps these discretes would be advantageous for active switching schemes so that the guitar could remain passive when not in sustainer mode. My understanding though was that boss stompboxes consumed power in bypass mode because of the fet switching, but I may be wrong. Anyway...when I can, I will attempt to listen to the guitar with a different pickup as a start. I do appreciate the engagement of everyone in our discussions, it is just so frustrating to get so close and yet all of us have consistently come across these blocks. My system does not squeal and EMI is low, it runs with reasonably low power (especially with a load or open secondary coil) and is better in all these regards to the thicker driver versions. It is more effective than the close and thin blade dedicated driver too. It is worth persevering with both this driver and the circuit with small modifications for now as there are significantly good things about it (simplicity, small size, low power) and no better performance from some of my previous attempts. Perhaps people will come up with some other ideas to try, either to test these ideas or some other areas to consider, or prospective solutions. pete Link to comment Share on other sites More sharing options...
psw Posted February 21, 2008 Author Report Share Posted February 21, 2008 Ok...so I connected a cheap 5.7k single coil pickup to a phone socket and rna that to the amplifier. I could hold it above the strings or mount below between the HB in the bridge pickup and the SC driver pickup. If it is possible for other to replicate this experiment I'd be interested to know your impressions. Basically this is a reverse eBow...the driver and pickup (as within the ebow) is in the guitar, nad the pickup is held above or below the strings on a complete independent circuit. You can run the pickup virtually (actually literally but there will be some interaction with the magnets) over the driver without too much squeal though the sound is quite a bit louder. It has some initial distortion due to increased volume if too close to the driver and cancellation effects if held over the wrong polarity pickup coil (my driver pickup as it happens is the old middle pickup so is reverse polarity as I recall). There is some initial ringing, perhaps fizzy distortion on pick attack that lasts a little while till it settles down to a clean no fizz sustain. On lower strings driven hard some fizz is evident. Holding the amplifier/pickup ground to the strings strangely enough did not seem to reintroduce fizz or produce any oscillation, but there was a decrease in background noise as the strings were now grounded to the amp as in a normal guitar. It would seem the fizz is not transfered into the strings. It is not a conclusive test by any means and I will keep the pickup about for further experimentation or if people would like me to try out some variations on this theme. Obviously something is going on, but I am too tired to make too much of it. As I say, ideally, someone will replicate this to see what results they garner. It does lend some support then to the notion of distortion entering the system via the hard wiring, as much as it does by EMI effects. Squeal is much more an obvious symptom of EMI and that can clearly be shown. I imagine that I will next have to rig up this driver in such a manner as to allow it to work far away from the HB bridge pickup (over the neck) and see if the fizz is still present at some distance, oddly, this is something I can't conclusively answer despite having done it many times in the past. Obviously squeal is reduced by distance, and I do suspect some distortion or fizz is transferred by EMI, but this simple test may also reveal something of the system characteristics and a combination of such experiments may well provide some reasonable answers. The pickup I am usisng is a very poor quality and overly bright. I may have detected a little more fizz at different locations along the string indicating a phase relationship, but generally if there is fizz, it settles down ounce sustain is fully established and the pick attack effects have subsided. pete Further update... I built a strat install in a cheap guitar that I described as "failed". The problem was controllable squeal. Since then I discovered the importance of the secondary coil. In order to operate 3 pickups with a 4pdt switch as I have previously posted, the pickups can not be connected to ground...as a result in this switch install, the pickups were left open. The result is a massive overpowering and so EMI everywhere. So, I cut the gain set pot leads (taht were soldered together and turned the gain set down as far as possible with the 1k trim pot and the squeal is controllable and and sustain present. I also note that with this pickup (metal poles with a copper shield and a ceramic magnet below) the device does not oscillate when the poles touch the strings. This leads me to wonder if there hasn't been some damage to the other guitars driver and part of the winding driver coil inner windings aren't in fact connecting with the poles or something. Though, I guess it would have to connect to all six which is a bit unlikely, will try and check it out some tomorrow. I have another driver to test also...this is a SCN fender dual coil telecaster neck pickup. It has a core so that gives me a little room to experiment further I guess. It also has a metal conductive but non-magnetic cover over the top and down the sides of the pickup to a separate earth and, like the noiseless pickup, is a dual coil stacked design with quite large side magnets. I will connect this into the test guitar and see if there are significant difference in performance and the action secondary coil(s) effect with this design. p Link to comment Share on other sites More sharing options...
psw Posted February 21, 2008 Author Report Share Posted February 21, 2008 HOORAY!!! fINALLY, A BREAKTHROUGH OF SORTS.... I replaced the single coil squire alnico poled pickup with a bridge noiseless fender model (unfortunately a little wide for the driver, but I can hold it on top for effect...and the thing is working beautifully!!! When I say working, the pickup is open (not connected even to a load) and there is no squeal when the strings touch the pickup poles (indicating a fault in the other one or something). There is absolutely no switch noise. Mind you, the pickup is not connected or switched so this is a preliminary result...installation issues often bring things a little undone. Best of all, it is running to tremendous effect with minimum power and right up to the point of squealing with little to no distortion, certainly no real fizz even in the higher settings and none at lower settings at all. Tomorrow I will wire it in and see if in fact the result is the same or similar with the switching. I can only conclude that the twin equal coils (and possibly the novel magnet arrangement, but I suspect this has less of an impact) creates equal and opposite forces within the poles and may even be canceling out some harmful eddy current effects. So, even though the driver is a very simple single (if ultra thin) coil, the combination of this with a dual coil pickup does at this stage address a lot of the problems I have been experiencing. Also, if this will run like this with the pickup disconnected, it bodes well for basic pickup switching. It remains to be seen if it stays noiseless and pop free when it is properly wired in. Looking at the an article (linked earlier) on transformers and a book I was looking at tonight, the combination of the low turns, resistance driver coil and the large number of turns pickup coil(s) means that enormous voltages will be induced in the secondary coil, but low current. I am not sure of the significance of this...obviously it has some effect...whether it is helping I really can't say for sure...that is where a more theoretical mind may need to be applied than I can muster. Anyway, it is such a relief as it means I can take a bit of a break then move ahead. It may mean, as a commercial proposition, that the driver requires such a pickup...a shame, but not impossible. I had been thinking that converting actual neck pickups into driver pickups may make for a better "product" anyway with less hassle than a kit to convert one. As for sound, these stacked coils have come a long way and I have been particularly impressed with these new generation versions in terms of tone, concept and build quality. I will now be keen to see if I can get a similar result with an HB version if tonights success still looks this good in the morning. It also vindicates my circuit and may make all these additional installation diagrams and schemes I have been doing lately, workable. There is no pumping of the AGC and some nice bloom to the notes (different and possibly superior in an expressive way to the sustainiac, depending on taste ) without it going too far. The lower strings are driving even more at the harmonic and perhaps some adjustment is necessary in this area. I suspect that the drive is sufficient (nice and string on the higher strings) to allow adequate drive even with lighter gauge strings (I use 10's). Oh...there is even a better harmonic mode response...much more powerful and more range, but still not effective over the whole of the guitar. On higher settings of gain though, I am getting nicer harmonics anyway that are touch sensitive and there are lots of areas to explore yet if the problems of distortions and switching have been addressed in this way. Anyway...obviously exciting and may in fact vindicate col's position on the ground loops and distortion issues regardless of the posts above. I think that it is possible that some things were due to some faults that distortions were getting into the signal somehow with my set up...but if this is working in this way now, then it is likely that a shared ground has little significance after all. More likely the coil was shorting on the poles (there seemed to be a bit of a sign of damage to the inner winding) and the single coil was causing some problems that the dual coils appear to have addressed. Try as I might, I am not even getting a click out of the switching...however, the neck pickup is not being switched in and out, so this remains to be seen if this continues in this way. Possibly I will wake tomorrow to find that it doesn't work so well...but it certainly sounds very promising tonight. Now I need to find a place where I can get cheap but reasonable quality generic stacked pickups to play with. WSC make one (STK50) I think that I have used before...anyone got any leads? I would like to play with some of these to see if the sound of these can be improved in line with the newer versions (they tend to sound brittle) and if they can work as well (thus discounting the novel magnet arrangements of these particular models). Thanks for your patience lately, I know I can be a PITA sometimes...will try and get some kind of sound samples up somehow... pete Link to comment Share on other sites More sharing options...
utopian isotope Posted February 21, 2008 Report Share Posted February 21, 2008 Nice to hear that you got good results psw! Sometimes hard working is PITA, but when it finally pays back, it is quite rewarding. ----------------------------- Anyway, I'm still stubborn about that common ground-situation. Just have to test all available things to get isolation between guitar signal and sustainer. Since I don't have any 600:600 audio transformers, I cannibalized one of my retired (originally 220V to 9V)wall adapter. It has 3.9/390 ohm coils, so I need to improvise with it... Link to comment Share on other sites More sharing options...
Fresh Fizz Posted February 21, 2008 Report Share Posted February 21, 2008 fINALLY, A BREAKTHROUGH OF SORTS.... Congratulations, Pete! A triple stacked coil. All pickup makers eat your heart out. utopian isotope, you did some experiments with metal sheets above your driver. If found this at the sustainiac website: 6. Metallized pickguards and guitar bodies. Also, metal pickup trim rings. These conduct electricity. The pulsating magnetic field that comes from the electromagnetic driver will produce pulsating electric currents in the pickguard or guitar body or pickup mounting rings. This will cause the bridge pickup to respond to these currents. The end result is poor sustainer performance. So, you must use a pickguard having no metal in the vicinity of the pickups (or scrape off the conductive shielding from this area). More you find here. Cheers Fresh Fizz Link to comment Share on other sites More sharing options...
col Posted February 21, 2008 Report Share Posted February 21, 2008 6. Metallized pickguards and guitar bodies. Also, metal pickup trim rings. These conduct electricity. The pulsating magnetic field that comes from the electromagnetic driver will produce pulsating electric currents in the pickguard or guitar body or pickup mounting rings. This will cause the bridge pickup to respond to these currents. The end result is poor sustainer performance. So, you must use a pickguard having no metal in the vicinity of the pickups (or scrape off the conductive shielding from this area). Good find. If the eddy currents in a sheet comparatively far from the coil have this impact, then those in the driver core could be significant? So, what effects could they be having ? Are we talking primarily about an unwanted magnetic field? Is it transmitting electromagnetic waves? Is it a bit of both. In the case of electromagnetic waves, an earthed copper shield like the one on the stainiac driver would certainly reduce the effect considerably - yet another thing to add to the 'TO TRY' list. It is interesting to note that for our purposes, eddy currents are 3 x bad - not only do they cause efficiency losses through heat and cause noise issues, they also generate a magnetic field that opposes that of the 'parent' inductor. No wonder the stainiac uses laminated cores. Col Link to comment Share on other sites More sharing options...
psw Posted February 21, 2008 Author Report Share Posted February 21, 2008 Well it was almost midnight last night when I made that last post. Now it is 8am... The thing is still working, however, while it is more efficient and can run with lower gains (resulting in less EMI) and the distortion is far less...some distortion is still evident, more so at higher levels. Not quite as bad and a bit smoother, more prevalent on the low strings. At the highest setting, I run it just short of squealing. I may switch to a larger pot so that I can get more low powered sounds. I just noticed that distance from the strings attenuates the distortions a little, moving the driver further away from the strings helps a lot. With a single coil driver you get more "throw" I found dual coil drivers required ultra close mounting and appeared more attentive to the effects of varying action (lower fretted notes are further from the driver and so are driven less). More important was the adjustment of the bridge pickup which is mega close. Anyway, I'm still stubborn about that common ground-situation. Just have to test all available things to get isolation between guitar signal and sustainer. As some distortion is still present, it would appear that it could be EMI...possibly into the strings after all and so into the ground. So, still a worthwhile pursuit if a good idea comes forward. I have a 300/300 transformer, but I am not sure that this wont mess with impedances... I also don't really think this is going to be that effective either...I would try the resistor and or capacitor ground lift options already presented first. Adding more coils may induce even more distortions and EMI problems. The reason being is that a transformer, capacitor or resistor will all still transmit AC signals and I suspect the distortion to is AC so wont be blocked by it...at least that is my feeling on it. Perhaps a better strategy is to try to filter out or cancel this distortion. With the present setup with triple coil pickup driver, distortions are only in the higher gain levels and in the lower strings. The distortions produced now may not be exactly "fizz"...it is quite attractive and may account for the touch activated harmonic response at these levels. This kind of response is exactly the kind of thing that I am looking for, but clean sustain and harmonics are desirable, if not more so, than distortion. It is no problem adding distortion with effects, but taking it out is hard! Another thing to consider is headroom. This is how far the thing can be driven without distortions in the drive signal. While 'Fizz' has purposely added it into his preamp, I really don't think it is desirable except for "effect". Consider this...eventually, when driven hard enough the device squeals. Just like a mic in front of a speaker, it is in an uncontrolled feedback loop resulting in oscillation (exactly like our pickup and driver, too close or too lound...squeal!). If you move the mic away from the speaker, you will find an area where it is just squealing, a little further and you are fine. However...the mic works now and can amplify close sounds like someones voice, but it will also amplify any other sounds it 'hears'...ambient room sounds and reverberations, etc. Included in this are the sounds of the speakers themselves. In a big stadium for instance, the distance to far off speakers can cause a significant delay before the sound travels back to the mic and results in an amplified echo of itself. This shows that the microphone picks up the sound of itself. No different is our arrangement...adjusting the bridge pickup to be very close to the strings so that the original sound is most dominant (just as loud rock stars learn to swallow the mic dominate their voice over ambient sounds (like marshal stacks behind them!!!!). This reduces distortion and provides a hotter signal to both the output and the circuit, resulting in less ambient sounds effecting the driver's signal. Now, consider this...if it is that, regardless of all precautions some sound from the driver will be "heard" by the pickup, what is the pickup hearing. If it is hearing a distorted signal from the circuit, it will result in "fizz", or at least some kind of distortion. I use an LM386 with reasonably low gain (now) and only buffering...but anyone who has heard such mini-amps or have connected a speaker to their sustain circuit know that this is hardly "clean". If inevitably the pickup will hear some of this (at higher gains or with less effective drivers pushed harder to compensate, etc) then inevitably it will hear "distortion". Consider also what it is hearing, not a speaker (which we know can sound distorted with these tiny amps) but reproduced electromagnetically through unusual "speaker coils" without cones! All speakers color the sound, perhaps our drivers color the sound, the amps distortions more "fizzy". On my set up, the fizzyness or grainyness is more apparent on the low strings. Perhaps they are vibrating a little louder, but I suspect that the very low output cap (100uF) struggles more with these low frequencies resulting in distortion not so apparent on higher strings/notes or as ugly! More distortion creates harmonic responses....my low strings virtually always sound at a harmonic (the low e, morphs to b above) and this is a cool effect. A higher value cap would get better reproduction of the lower strings without this effect and probably less distortion or fizz. The expense has been in high string response however, which is why I do it. Another approach would be to have a woofer/tweeter kind of arrangement for high and low strings (consider my Hex designs with separate drivers for each string), an adjustable output cap for different effects or a wider ranging driver response. Another strategy which I seem to be exploring lately is to make this distortion more attractive and exploit the harmonic effects that are created by a distorted signal, even if at those levels distortion is present in the output signal. As long as it isn't ugly and "fizzy" and you can do clean sustain at lower levels, this is less a problem but a feature. ---------------- This is a simple explanation of some of the distortion effects, but that is not all. I do think that some signal is being transmitted into the guitars wiring and Sustainaic repeatedly warn of "grunge" distortions being transmitted if precautions are not taken (moving the driver wires away from signal wires, metal pickup rings, etc...) to avoid problems like this. So...there is still room to explore ground and EMI noise issues...but something that has not been adequately explored perhaps is basic clean headroom. With an amp powerful enough to run well below it's capacity to deal with the spikes created by pick attacks and energetic string vibrations and capable of dealing with the kind of power pickups, especially high powered ones designed to overdrive guitar amps, will put out (even more so if adjusted very close to the strings and maxing out their output as I have suggested above). I propose then to test this out in the near future with more powerful small amps...I suspect that these, running with a reduced input (for a cleaner signal) and at levels below their capacity will address the "problem" at least to some degree. The problem is will it be capable of working economically on battery power. ----------------- There are a lot of interesting stuff in that Sustainaic link and associated documents and I think some time could be given over to discussing these and their implications also. One thing that I noticed in the power section Suatainiac Power Options is that they suggest two batteries and while outboard power is an option, it can't be done on theirs with a stereo lead as the power consumption (60mA) is such as to cause noise with the shared earth...hmmm, sound familiar?! You can run it but with separate power adapter and power leads. This is an important point. An amplifier can only reproduce sounds in proportion to their power supply capacity...which with a 9 volt is small (in voltage and more importantly, current capacity) and with the kind of strain put on a battery by this kind of circuit, the power capacity is significantly reduced with use. One of the first things you notice with diminished battery power is distortion..."fizz". Obviously, as an amp struggles with power capacity it's clean headroom is reduced and so distortion sets in. Outside reliable power, especially given the consumption would be preferably, but sustainiac seem to indicate that shared grounds will cause problems with the amount of power being sent through it. Any strategies that avoid two leads into the guitar would be appreciated....how does USB transmit power and ausio without noise for instance? ---------------- Not being capable of the mental gymnastics right now to properly get a handle on it, similarly, when turning down the guitar's volume, input is reduced. Perhaps this is a bit like the rock star pulling the mic back from his mouth and the ambient distortions getting through (or lowering the bridge pickup)...I am not sure. Everyone should see if they are getting increased distortions with guitar volume reduction and if so, try and analyse and describe it's effect. To me the effect is to roll off the signal to reveal any hidden or not so hidden fizzyness behind the note. The sustain continues, but the "fizz" remains fairly constant (till towards zero where no sound is heard, fizz or otherwise, yet the guitar sustains just as well as if on 10). ------------- Other factors in last night's success is that as well as a different dual coil design, the noiseless designs have a different magnetic arrangement (although this vintage version seems to lack the side magnets of the hot and SCN versions) and a far superior build quality. While the original SC was pretty good and wax potted, this is a better pickup. As far as the switching goes...it is still silent, but then it is not in anyway connected to anything. There may well be problems with the mechanics of the switch...so we will have to see if it remains silent after install. -------------- I hope all this is of benefit and better explains things. Correct, ask questions, discuss or add further observations into the mix. pete Link to comment Share on other sites More sharing options...
col Posted February 22, 2008 Report Share Posted February 22, 2008 (edited) Heres a femm plot I made a long time ago (sept 06). It shows how the strings can provide a nice channel for the flux from the drive to easily reach the pickup. This has nothing to do with anything getting into the earth - it is purely about the coupling of the megnetic fields. I guess that the reality is not so extreme - the effect is less than shown here due to the plot being 2D. Additionally, there will be a limit as to how much flux the strings can carry - they must reach saturation pretty quickly. A nice way to test this would be to take all but one string - B would be good - then see if the fizz is better or just the same. If this effect is a major contributer to the fizz, removing all but one string should reduce fizz significantly. (Of course, we would still need to work out if any eddy currents in the strings are more significant that this magnetic effect.), but at least would would be narrowing things down further. Unfortunately, as usual I'm not in a position to try this out right now, but will do soon. heres the pic As to how we could 'solve' this if it does turn out to be an issue - thats tricky. Obviously we can't stop the flux getting to the strings from the driver or from the strings to the pickup - both of those channels are imperative to system functionality. The only options I can see are: #1 Keep the fuzz - its a feature not a problem #2 Reduce the gain to prevent clipping so that the coupling is not audible - masking (what my circuit does - has its drawbacks) #3 Find some way to create an opposing fizz that provides cancellation. I personally really want #3 to be possible One immediate benefit is that this approach is flexible and could potentially be used to cancel fizz from other sources as well. The flip-side is that to even start to try and do this we have to have a good understanding of what causes the fizz, how and significantly what the phase relationship is between fizz and drive signal. How we might go about doing it is another thing entirely cheers Col Edited February 22, 2008 by col Link to comment Share on other sites More sharing options...
psw Posted February 22, 2008 Author Report Share Posted February 22, 2008 Here is an interesting symptom... I have yet to wire in the dual coil pickup, so it is too early to say if it does not suffer the same symptoms on full installation that the last one did. There may be other faults at play that effected the performance as I did get this to work on a previous version with the same pickups... Anyway... If the guitar is making sound...sustaining away...typically you can turn it off pretty silently. With no pickup connected, it works silently (bridge and driver only installed) if no sound it makes twump...slightly worse if the selector is in neck position (perhaps, only slight). If the driver is removed from the pickup, switching off and on is silent. Typically on switching regardless is completely trouble free. As I say, a little early to say if a stacked pickup cures this or if the success of this type with the driver is entirely due to this factors or if the other pickup has some faults I can't detect. Further tests to follow...I have to question if the switch is truly make before break however and if this is not the problem. Otherwise, perhaps it is time to insert some filtering caps to slow down the thump...perhaps a resistor an cap in the earth, perhaps I need to look into the potential for driver switching. Any thoughts appreciated... pete The only options I can see are: #1 Keep the fuzz - its a feature not a problem #2 Reduce the gain to prevent clipping so that the coupling is not audible - masking (what my circuit does - has its drawbacks) #3 Find some way to create an opposing fizz that provides cancellation. I personally really want #3 to be possible smile.gif A reasonable summation... I was wondering if my secondary coil could perhaps be used to generate a fizz canceling signal. It wouldn't have to be a pickup but an additional coil or something in a stand alone design might work. #3 would be cool, but difficult. By #2 I imagine you are talking about using gain lower than the fizz threshold. I think this is in part what my single coil drivers do with good throw and efficiency, these ones appear to be creating a better effect with far less power than the older DIY versions and certainly any dual coil systems I made (though this was limited and rail in size). #1 has some very interesting effects. It is the main differentiating factor of what my system sets out to do and the sustainiac et al. At low gains you get clean relatively distortion/fizz free sustain. At higher gains (by gain I don't mean that the guitar gets louder, it doesn't) there is some distortion...as I was trying to suggest in the post above, if that distortion is attractive (unlike the typical fizz) you can get a nice soaring sound and the distorted signal brings up the harmonic content of the signal meaning that you can ping off harmonics with pick attack and strength that is very effective and expressive and quite different from the harmonic switch effect. Still though, my harmonic switch function works only on lower strings effectively, although improved with the stacked design. I really believe this is a phase issue now. So...#1 is a very worthwhile area to explore as long as #2 is effective...#3 would be nice, but could introduce more problems (cancel out more than the fizz for instance, creating it's own tonal effects) and could be very difficult to achieve. The kinds of distortions produced by the device can be a lot less mushy than distortion units produce and have an interesting polyphonic quality also...so all would not be lost if you could get #1 to sound great! anyway...must run... pete Link to comment Share on other sites More sharing options...
col Posted February 22, 2008 Report Share Posted February 22, 2008 I really believe this is a phase issue now. I am 99% sure there is a phase issue involved. I'm also pretty sure exactly what. It's also likely that theres more too it than that. However, it will probably be enough just to solve the phase issue. That said, it doesn't really bother me, because I don't particularly like the inverted signal harmonic mode. So...#1 is a very worthwhile area to explore as long as #2 is effective...#3 would be nice, but could introduce more problems (cancel out more than the fizz for instance, creating it's own tonal effects) and could be very difficult to achieve. #1 is just there - change the range of gain to include or exclude it. #2 is effective - I have used it effectively in my existing system, it works very well, but as I have stated many times, this approach does cause restrictions that I have explained. These cannot be 'fixed' by using a bigger amp - they are inherent to the approach. #3 is going to be tricky. I'm sure its possible, but whether its practical for any of us is another matter. To make a noticeable improvement to the system, it might be enough just to reduce the fizz. This is a much more achievable goal, so even if total fizz eradication is out of reach, there can still be benefits from going down this path. The kinds of distortions produced by the device can be a lot less mushy than distortion units produce and have an interesting polyphonic quality also...so all would not be lost if you could get #1 to sound great! Hmm, gotta disagree with you there - IMO the 'fizz' is an indistinct noise that takes some of the edge and clarity from the true sound - its not _really_ bad, but it certainly isn't a desirable sound. In all the years I've played, there are many many 'fuzz' sounds I've had in my head that I've tried to achieve - often successfully. The sustainer fizz is not one of them - not even close. If I made a stomp box and it made that sound, I'd be checking the circuit for errors or bad components! cheers Col Link to comment Share on other sites More sharing options...
utopian isotope Posted February 22, 2008 Report Share Posted February 22, 2008 (edited) One thing that I tested, was lowering sustainer's supply voltage to 5V(with 7805). Result? No more higher strings feedback. Question is: higher the supply voltage, higher the driver's(or sustainer's?) effect on higher strings? Anyone tried it? Higher supply voltage requires some step-up transformer also? Although you get quarter of the current out of secondary coil. Don't know which is more important, voltage or current. Anyway, just a thought. Edited February 22, 2008 by utopian isotope Link to comment Share on other sites More sharing options...
psw Posted February 22, 2008 Author Report Share Posted February 22, 2008 Question is: higher the supply voltage, higher the driver's (or sustainer's?) effect on higher strings? No I just think the amp is struggling more now that it has less power and your high strings are operating not from the effects of raw power but driver inefficiency. Perhaps it's time to experiment with a new driver. It sounds as if a lot of what you have innovated (the squeal reducing loop, etc) has been in an attempt to get the performance you would already achieve with a better driver IMHO. Sure I get squeal at high gains and if pickup too close to driver, but this occurs well above infinite sustain and general fizz producing power and all the strings respond well. Also, are you using light strings...this wouldn't be helping response...10's are recommended. I am 99% sure there is a phase issue involved. I'm also pretty sure exactly what. Do you get more "fizz" on the lower strings and notes as I do? I have a feeling that our uncompensated amps produce distortions due to the lag in driver response and in relation to delays from the output amp and other components. I have been seeking a window of operation that will work, and in general I think I am getting a response at low driver gains pretty clean. The lower strings reveal a grainy distortion first, perhaps these slower frequencies reveal it more readily, as phase is frequency responsive. At higher gains it is evident at higher frequencies (still more on the lower strings however)...perhaps more power into the driver makes the lag (the time it takes for the drivers electromagnet to change magnetic states). If a secondary coil could help with efficiency or distortions, then perhaps it is in taming eddy currents and addressing the "lag"...although I have only observed the effect and I am not sure that it reduced fizz in the formats I have tried. The stacked pickup my simply nullify the effect without adding a load... #1 is just there - change the range of gain to include or exclude it. Well, that has been the approach and attitude I have had with this thing. The distortions at higher gains are very effectively masked by any overdrive on the amplifier and when tested with a valve amp, creates a nice warm glow to the sustained notes. These days I am less inclined to test with the valve amp (fender deville), instead I test into a little (15 watt on 1) tranny practice amp, sometimes with a digital effects pedal (korg AX1G) on a clean setting to reveal as many of these "problems" as possible. The distortions or fizz appears to shadow the notes...I still get clear signals from the vibrating strings but with a distortion sound behind it, almost as if in stereo with one side effected. I also get different types of distortion...not everything is a grainy fizzy, unattractive distortion. Hmm, gotta disagree with you there - IMO the 'fizz' is an indistinct noise that takes some of the edge and clarity from the true sound - its not _really_ bad, but it certainly isn't a desirable sound. On the other hand, this is true too. Ideally a completely distortion free response is desirable. It might be possible to make the fizz more attractive as a distortion. The last player I demonstrated it to, actually liked the distortion produced (though now I think about it I was running it into a clean valve amp so perhaps the overdriven sound was more attractive on this occasion because of that). To me "fizz" implies a bee in a jar distortion (quite popular a decade ago or so as I recall)...if some of this is a given and can be altered by different circuitry or driver/pickup designs of configurations, then this is a valid direction. The up side is in the improved and touch sensitive harmonic response possibly created by the distortions in the driver signal at higher gains (remember the guitar itself does not get louder). At least the "fizz" is related to the note...it isn't "static" or indistinct noise. However, I am not "advocating" distortion...if some of the touch sensitive harmonic effects and note shaping at the higher gains that I am getting are distortion related then this is an area I will be seeking to employ. In comparison with my short experience with a sustainiac, this is what really told it apart, the expressiveness of it...the dynamics and tone range. The sustainiac produces a clean even sustain across all strings...however it did seem a little "squashed" in performance, less "lively" compared to my "system". Perhaps though all our "fizz" effects are different in sound. All the same...fizz should only really become an issue at high gains with an efficient driver. I will be looking forward to building an HB sized driver to compare with the SC unit I am working with at the moment. --------------- On to the switching problems... I was trying to think of ways that a 4066 could be used to switch pickups or cause short delays without having to remain active. I imagine a capacitor could store enough power to slow release these. The 4066 is 4 spst switches normally open when unpowered. Perhaps some kind of FET normally closed could be used to disconnect the neck pickup and slow release it back into the guitar circuit on switch off...any thoughts, anyone? I can see how it is possible with one of these to easily switch both the driver and input signals of the circuit out on switch off, but I am not sure that this addresses any real problem...but who knows...any ideas as to if this would help? ----------------- I bought some new batteries yesterday and just trying them out (super alkaline) there is a significant improvement in distortion/fizz removal (could drive far stronger without fizz) and generally a far greater performance. #2 is effective - I have used it effectively in my existing system, it works very well, but as I have stated many times, this approach does cause restrictions that I have explained. These cannot be 'fixed' by using a bigger amp - they are inherent to the approach. Based on this result, cleaner headroom from improved power supply, it would suggest to me that an amplifier that produces more or the same gain range with less distortion is a significant factor and improvement in all areas (except switch noise!!!). An LM386 is notoriously fizzy at high gains and with a low output cap like I use, probably more so. However, it is sufficient if the driver is efficient enough to run it at low gains. I really need to try and get some sound clips posted some how...I have the web site, now I need more guidance on how I can use this facility...any takers, as I could probably not only post my own sounds but small clips of others to compare?! pete Link to comment Share on other sites More sharing options...
psw Posted February 23, 2008 Author Report Share Posted February 23, 2008 I took the guitar apart and tried a few other options with it. The original SC pickup that the driver sat on was shorting...a bit of the epoxy and insulation had rubbed off the inner windings from repeated taking on and off of the device (it wasn't really designed to do this...supposed to be fitted and thats it)...this is the reason it screamed when the strings touched a pole and why earthing of them was not possible. Grounding a string to a pole now causes no noise, maybe a slight reduction in background noise possibly fizz, but it is hard to say...generally it seems to make no difference. I have also been able to try the ultra thin driver with a core and ceramic magnet on the back and it works superbly as a stand alone driver. Hard to tell yet if the secondary coil idea helps or hinders...it certainly appears to do something... Still got the turn off clicks!!! pete Link to comment Share on other sites More sharing options...
Fresh Fizz Posted February 23, 2008 Report Share Posted February 23, 2008 I did some tests with my Handyprobe (oscilloscope on PC). I found out that the appearing wave forms are pretty much sine wave. So even with a lot overdrive the feedback will settle in a more or less sine wave-y tone. I did the test only for fundamental mode. There is no harmonic mode on my guitar. Maybe it is due to the overdrive but I only get 3rd harmonics below the 12th fret position. Above the 12th fret it's all fundamentals. Is that normal? I would have expected positions on the fretboard with a 2nd harmonic. I use a 660u (2 x 330u) output cap. One thing about the fizz. I found out that the fizz is most anoying when you hit the string softly. Then the driver causes some sort of volume swell which sounds very fizzy. Cheers Fresh Fizz Link to comment Share on other sites More sharing options...
col Posted February 23, 2008 Report Share Posted February 23, 2008 (edited) I did some tests with my Handyprobe (oscilloscope on PC). I found out that the appearing wave forms are pretty much sine wave. So even with a lot overdrive the feedback will settle in a more or less sine wave-y tone. The easiest way to think about this IMO is to use the Helmholtz model and think about what happens when the kink is between driver and pickup (although, I'm sure you can do the math with a superimposition of sine waves and get the same result). Basically if the phase relationship between the driver field and string for that string/fret combo is not exactly 0º, there will be active damping of the overtones - the worse the phase difference, the quicker the sound will revert to a pure sine wave. Using a square wave as a drive wave will only help to keep some nice overtones in there if the phase is well matched. Maybe it is due to the overdrive but I only get 3rd harmonics below the 12th fret position. Above the 12th fret it's all fundamentals. Is that normal? I would have expected positions on the fretboard with a 2nd harmonic. I use a 660u (2 x 330u) output cap. This is common (I think?). Most likely caused by a combination of phase difference due to the driver/pickup gap, and the fact that the driver becomes less efficient as the frequency rises. You could probably tweak the design to give harmonics higher up the neck, but then the response would certainly change nearer the nut - either losing harmonics, or losing sustain in general... One thing about the fizz. I found out that the fizz is most anoying when you hit the string softly. Then the driver causes some sort of volume swell which sounds very fizzy. Yes, I think the cause of this is a significant factor when trying to understand 'fizz' in general - and how we might remove it. Fizz isn't all 'just there' from the start of a note - there will be some during the very loud attack portion, but the fizz during a note can also build through feedback. If you're using high gain and no AGC, then when there is a strong guitar signal, much of the fizz component of the sound will be lost through clipping, so you tend to get just 'fresh' fizz, rather than recycled fizz build up - this will sound a bit like a poor quality distortion unit in the background - it's almost acceptable. When on the other hand you have a low level guitar note, the fizz won't be smashed by the clipping of the guitar tone and gets nicely amplified. It then is more readily transfered to the pickup directly through parasitic coupling. And then amplified some more, added to more fresh fizz and the process repeats, so the fizz not only becomes a more significant part of the sound, it also becomes less and less connected (in time) to the note you are playing... so it's becomes more like a background noise than a guitar distortion sound. This means that it might be possible to make a significant improvement without actually removing all fizz - if we can in some way stop the fizz feedback building, or limit that process? ----------- BTW, it makes sense to me that squeal is oscillation caused by the actual guitar sound feeding back through direct magnetic or electromagnetic coupling between driver and pickup whereas fizz is caused by amplification and feedback of the _difference_ between the guitar tone and the driver signal - particularly the difference in the harmonic spectrum of the two. Probably obvious, but I don't think it has been stated in this way. That is why the loop trick can fix one without fixing the other. Btw Fresh Fizz, is your scope dual channel ? It would be very useful to see a plot of the phase difference between the driver signal and the signal from the pickup - when playing different notes on different strings. cheers Col Edited February 23, 2008 by col Link to comment Share on other sites More sharing options...
psw Posted February 24, 2008 Author Report Share Posted February 24, 2008 Hmmmm.... I wonder if we are all talking about the same thing. "fizz" I don't know if it was missed in my overly long posts but I do have some web space paid for now that cold be put to good use and is adequate for storing and accessing audio files. I'd be prepared for this to be used while I am not using it to further the project but I may need some assistance. Otherwise, I guess soundclick is the go. I will try and get some sound up so that it can be judged for what it is..."fizz" is a pretty loaded word and we may not all have the same kinds of sounds coming out. For instance, col...I thought (and from the clips I had heard) that your AGC circuited dual coil driver single pickup guitar was running pretty clean. My distortion effects come in at higher gains in the main. What can appear at lower gains is fairly subtle and more as you describe as a kind of background distortion, the sustained note tends to ring continuously fairly true. BTW, it makes sense to me that squeal is oscillation caused by the actual guitar sound feeding back through direct magnetic or electromagnetic coupling between driver and pickup whereas fizz is caused by amplification and feedback of the _difference_ between the guitar tone and the driver signal - particularly the difference in the harmonic spectrum of the two. Probably obvious, but I don't think it has been stated in this way. That is why the loop trick can fix one without fixing the other. No...I don't think it has been expressed so well or is obvious. I think this is certainly something to ponder deeply...hmmm I do think phase is a factor in all this and lots of little "symptoms" can alter the distortion effect (vibrato for instance seems to clear it up sometimes due I guess to some pitch modulation). However, if there is phase cancellation, why is it that there isn't a dramatic change in tone with this fizz, shouldn't it be canceling and reinforcing frequencies at the same time it is distortion, not just hovering in the background. This type of effect is exactly the kind of thing I now get from my harmonic mode on all but the low strings. If you're using high gain and no AGC, then when there is a strong guitar signal, much of the fizz component of the sound will be lost through clipping, so you tend to get just 'fresh' fizz, rather than recycled fizz build up - this will sound a bit like a poor quality distortion unit in the background - it's almost acceptable. When on the other hand you have a low level guitar note, the fizz won't be smashed by the clipping of the guitar tone and gets nicely amplified. It then is more readily transfered to the pickup directly through parasitic coupling. And then amplified some more, added to more fresh fizz and the process repeats, so the fizz not only becomes a more significant part of the sound, it also becomes less and less connected (in time) to the note you are playing... so it's becomes more like a background noise than a guitar distortion sound. Some of this is what I was saying...transfered to the pickup directly through parasitic coupling means that the pickup "hears the driver" as I was kind of putting it. However, you have gone further that is interesting, what it hears is further amplified and this too is phased and added to it. Interesting...so why does this fizz not overwhelm the sound of the string and become dominant? It must surely continue to build and build...or am I missing something. I would also have expected that the fizz would evolve, as it gets further out of phase (delayed in time) with itself or the note that generated it, why then does it not then modulate, eventually for instance the fizz may reasonably cycle back to being in phase and clean up momentarily...or am I missing something with this theory. Also, if the thing is "hearing itself" or transfered to the pickup directly through parasitic coupling, if what it hears is not distorted, should this not be less inclined to "fizz". Hence my desire to obtain an amp to test this idea a little further by supplying cleaner headroom...but you don't feel that this will help? It would seem to me that a well constructed and executed device can run at low levels without excessive or any fizz. Is it your conjecture that this is purely down to EMI reduction, localizing the fizz around the driver so that the pickup is unable to "hear" it? That makes sense and is in line with our work so far. Continuing to try and make better and more localized driver designs may well be advantageous then. Because I am at present committed to exploring this design that I am happy displays admirable qualities in this regard (EMI localization) speed and efficiency...and it's application, I am concerned more that any distortion that does appear is not an electronic fizzy artifact but a useful, harmonically rich distortion when run at levels that it appears. If you're using high gain and no AGC, then when there is a strong guitar signal, much of the fizz component of the sound will be lost through clipping, so you tend to get just 'fresh' fizz, rather than recycled fizz build up - this will sound a bit like a poor quality distortion unit in the background - it's almost acceptable. I am using fairly low gain, no preamp gain and some AGC, while I agree a poor quality distortion only appearing at higher levels of drive is "almost acceptable" but I think it can be improved to be a usable effect if you want to 'overdrive' the strings with excessive gains in the circuit for various effects. Maybe it is due to the overdrive but I only get 3rd harmonics below the 12th fret position. Above the 12th fret it's all fundamentals. Is that normal? I would have expected positions on the fretboard with a 2nd harmonic. I use a 660u (2 x 330u) output cap. Well...I think that the overdrive does produce harmonic effects which can be quite food and your idea of clipping the preamp signal may well have merit for an "effect" as discussed by col and above, but probably detrimental in the pursuit of clean and reliable sustain effects...but I think I have suggested that before. If possible I would disable the diodes to get a clean signal an see if this helps. I am not familiar with your amplifier, so I can't really comment on values. You haven't considered building a smaller LM386 based unit such as col and I are using for comparison purposes...it is hard to even determine the efficiency of your driver and how effective this is when every component is different. I use a 100uF generally to ensure strong high string response (with my circuit) all the way to the top most strings and frets. I get an emerging harmonic on lower strings from about g (fifth fret g string) down to the low e. The effect and speed in which the harmonic "emerges" depends in large part to the amount of drive. The effect is also affected by the closeness of the driver to the strings and the pickup so it is a bit adjustable...again, really play with pickup (generally as close as possible) and driver heights (adjusted for best response between strings). However, fizz effects are more prevalent on the lower strings as is thi9s harmonic effect...as you suggest, perhaps related... It also reminds me, I did think about your suggestion of running the pickup coil (about 5,600 ohms) in parallel with the driver (this one about 8.2 ohms) but calculating it out (which I am not good at BTW) I got 1/8 (0.125) + 1/5600 (1.79) = 1/ (1.915) = 0.522 ohms Half an ohm is going to be far too low to be driven by these circuits. It is an interesting idea (if you ignore a lot of other considerations though, and I am prepared to do a little practical experiments with it. So...would someone like to have a guess at the value that the driver (the first figure) would need to be to get a parallel outcome of around 8 ohms? I had forgotten this, but I wonder if it is possible that your output caps are in series resulting in a similar reduction in value...the formula is the opposite to resistors that increase with series...correct me if I am wrong. It cam to mind because your description is in line with the effects I get if I reduce out put caps and if I was running 600uF on mine, I would be getting strong fundamentals, probably at the expense of high string response. You may wish to check this. ----------- I have been working on some switching ideas. I am considering adding in a 4066 quad spst switch. These are normally open and so if wired to trigger with on power could be used to connect stuff only when power supplied and so, if not used for critical signal stuff, the guitar could remain passive (which BTW the sustainiac can't really) without power (one of my aims). I was thinking of using one switch with a capacitor feeding the CV trigger signal so that it would "hold" a little after power sut down as the cap discharged. I get silent switching for instance with the neck pickup shorted so if this was done on the circuit and it became unshorted, with a slight delay, then perhaps this would fix the occasional twump effect on switch off. Additionally, I could use one switch to immediately disconnect the driver's ground connection on switch off. With two more switches available there is even a potential to lift the signal into the circuit (not that this seems to be a problem) connecting only when power applied to the circuit. An interesting potential arises from this last application, I use a MosFET to cut the signal above certain levels of output as an AGC, this is small and neat, but perhaps a CV could be generated to switch in and out one of the 4066 signal lines to cut signal when it rises above an acceptable level and reconnect if the string begins to die back... Other switching thins is that I am going to try and use the other side of the strat's basic blade switch. This is not required with a master tone and so can be used for other purposes, chiefly separating the bridge and other pickups and tackling the problematic combination (particularly position 4) that can arise with a conventional wiring. I am trying to get it down to a dpdt switch for on off function still and am looking for further ideas if anyone wants to engage with this frustrating and puzzling occupation. I am hoping that an answer will arise from the combination of a 4066 in use as above and the dp5t blade switch. ------------ Additionally, with the recent successes I was tempted last night to stick a middle pickup back in the test guitar. I will miss the neck and bridge pickup combination, but I was messing about with ideas on paper and came up with a cool super easy mod. If you take off the neck and middle connections to the selector switch and swap them over, instead of b, b+m, m, m+n, n you would get b, b+n, n, m+n, m Might take a bit of getting used to, but this means position 4 is b and neck and you still get the other combinations. This would be really useful with an H/S/S strat as typically, without splitting the bridge HB and the middle produces a very thin tele like bridge tone with no quack. The bridge HB and neck SC is possibly more desirable and it is an easy mod (two wires) easily reversible. Just a thought...may post this elsewhere as an idea for general consumption. ----------- It may be (a little early to tell) but sticking a pickup between the bridge pickup and driver may be advantageous. It seemed, although unconnected, that it did create a bit of a magnetic shield effect (it is opposite in polarity to the neck pickup) jst by being there. In col's FEMM drawing he illustrated the possible effects of the driver running along the strings, one would expect a big magnet such as a pickup to affect this "effect" or otherwise effect the EMI radiation into the bridge pickup. Of course, if not carefully handled in installation, another pickup creates even more headaches! ------------- Speaking of which, I've got one now...so must away...interesting stuff...carry on! pete Link to comment Share on other sites More sharing options...
Setain Posted February 24, 2008 Report Share Posted February 24, 2008 It also reminds me, I did think about your suggestion of running the pickup coil (about 5,600 ohms) in parallel with the driver (this one about 8.2 ohms) but calculating it out (which I am not good at BTW) I got 1/8 (0.125) + 1/5600 (1.79) = 1/ (1.915) = 0.522 ohms You made one mistake: 1/5600 does not equal 1.79. It equals 1.79 x 10^-4, ie .00179, which means that the resistance would be 7.99 Ohms. Next time use (R1 x R2) / (R1 + R2). Trust me, its easier. Link to comment Share on other sites More sharing options...
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