Fresh Fizz Posted February 24, 2008 Report Share Posted February 24, 2008 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. I don't think that the phase issue is a big problem. It can be split up into 3 areas: pickup, driver and electronics. For the driver I allready gave you a way to calculate phase shifting. Here is my document to calculate the phase shift of the driver. For the pickup you could do the same calculations, but it's a waste of time. Any decent pickup well extends the range of 1100 Hz. Unless you have some kind of superdistortion very ugly metal humbucker. What electronics concerns, if the signal is only amplified without any toneshaping (eq) there won't be much phase shift. About Helmholtz: I found this interesting link. I think this and also this links show the real problem to solve to achieve fundamentals below the 12th fret. The java applet shows that the fundamental is around 10 dB weaker than the 3rd harmonic (pickup at some 2" from bridge). So the fundamental cannot compete with the 3rd. 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? I fully agree with you. Something out of control, like driving off a cliff. How about slew rate limiting? 1 , 2, 3 Btw Fresh Fizz, is your scope dual channel ? No, it's a prehistoric version the name scope unworthy. I bought it for my at 286 (remember ?). It won't work under Windows. I need to boot if from floppy without the himem.sys and no chance to read my harddisk partitions. 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. Well my sustainer device produces a lot of "dirt" but I think that they are 2 different phenomena: harmonics created by overdriving the fet + clippers and the fizz. I think Col's description of fizz comes very close. 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. No they are in parallel. Mind you, all the trouble to squeeze in an extra cap only to get less fundamentals? 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 Question answered by Setain. I was thinking Pete, have you ever considered of skipping the neck pu. Why don't you use the driver as pickup? What you need then is a noisefree microphone amplifier. And the switching system had to be rock solid of course. You don't want a few volts on your microphone amp. But maybe you want to keep it passive. I think that is what the commercial guys have done. Somebody mentioned a transformer, I think it is a step-up transformer for the driver. But I am not sure I have never seen a sustainiac in my life! Cheers Fresh Fizz Link to comment Share on other sites More sharing options...
psw Posted February 24, 2008 Author 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. I thought there was something dodgy with the calculation...ok, that gives me something else to experiment with... I should never be trusted with maths, and although I try hard, some things are not in my skill set so my eyes do kind of glaze over with a lot of theory. -------------- Meanwhile...so very frustrated...came up with a u-beaut dpdt passive switch cheme... and it kind of worked...and now I have other problems...doh!!! When it's working it's great, but adding that extra pickup did complicate things and losing half the pickup power (from a 4pdt) was ambitious...but that is what I want so I thought I'd try at least. I was thinking Pete, have you ever considered of skipping the neck pu. Why don't you use the driver as pickup? What you need then is a noisefree microphone amplifier. And the switching system had to be rock solid of course. You don't want a few volts on your microphone amp. But maybe you want to keep it passive. I think that is what the commercial guys have done. Somebody mentioned a transformer, I think it is a step-up transformer for the driver. But I am not sure I have never seen a sustainiac in my life! Yes...well sustainiac do use the driver as a pickup as do fernandes.. You guys seem content with a single pickup instrument and to that extent, my guitar will work perfectly. The problems I am trying to tackle is integrating the single pickup driver back to a three pickup 5 way selected strat with a single switch, no noise and complete bypass and still be passive. Until recently, I had not seen either. The fernandes is the one with a small transformer. Both have fairly large circuits and drivers. I am trying to approach it in a different way and a different kind of performance and sound too...not just the infinite sustain so much as an expressive soaring sound and new techniques for envelope shaping and harmonic production. It is hard to explain what is in ones head, but I guess it is something like the expressiveness you can obtain with a loud distorted guitar but with low volume, complete control and little or no distortion. I also want to retain the characteristics of the guitar and have this ability to add to the instrument without sounding like an "effect", so the character of the guitar should remain constant. The sustainiac was very good but there is something in mine when it is working properly that is quite different and very expressive and organic. The sustainiac does sustain ok and the neck pickup does sound ok too. I am getting powerful clean sustain, very little dirt or fizz except when the thing is pushed...and that sounds a bit more like an effect, but then it is dialed in and the character remains. It is also fairly touch sensitive. I certainly appear to be getting out of my depth with some of this, but I think we are all working on different devices and approaches and perhaps even to different ends. Still, the technology is pretty much the same. My device also works as a stand alone driver very well. I had planned a telecaster version, but it is apparent that the metal cover interferes dramatically and it is smaller and there are other problems with converting this. I plan then to modify it into a stand alone driver that sits next to the neck pickup. All the same, all the same problems of switching exist whether built onto the pickup or next to it. Most if not all of my present problems exist only because of the multiple pickup scenario. It was only recently that I appreciated the significance of the secondary coil in the equation. Previously I had shorted the pickup coil as a matter of course, I can't remember (it was a few years back now) why I originally did it, I must have discovered this problems and that shorting it fixed it so continued regardless. The dual coil stack pickup did not seem to require this shorting (which makes switching easier) so perhaps I should look into making a specially designed pickup/driver based on the design. Basically I am at a stage where I can get a sound I am happy with, as long as I am only using the bridge pickup (as you guys do). I even get no switching noise in this configuration. The loss though of all the other pickup sounds when the thing is off is too great. I do not want to make a one trick pony but an excellent working guitar plus the ability to play long and harmonic notes as required. I don't think I need explore "better" driver designs at this point...the thing has proven that it can work. Even the circuit produces the results when it wants to, tweaking it is an option but for now it does the job. No, the problem is not that it doesn't work, it is all in the integration of the device in the guitar. It seems insurmountable in the format I have. Taking it off the pickup didn't help and so, making it into a pickup wont solve the integration problems, just add more power and switch problems I suspect. Perhaps I need to make the entire guitar active, look into remote power (I am eating batteries here and it does get expen$ive) and perhaps this would aid it (the power would remain on the whole time and batteries would no longer be an issue). As it stands, I am at a bit of an impasse...need to sleep on it, getting late... ----------- If the combination of the pickup and driver works out to be about 8 ohms as is suggested, then I will try connecting the driver and pickup coils together...it kind of goes against my ideas of the thin fast driver and I am not sure that it would really work, but it may address some other problems and we wont know if we don't have a go...thanks for clearing that up for me. pete Link to comment Share on other sites More sharing options...
col Posted February 24, 2008 Report Share Posted February 24, 2008 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. I'm don't understand why that would be the case? 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. Each time round, it becomes a bit more out of phase with the fresh fizz being created, so after some number of iterations, there is cancellation - both of some of the new fizz, and some of the old fizz... this prevents it from snowballing into squeal... it also accounts for the effect where the fizz is loud for a short while then magically clears up quite a bit. The 'old' fizz cancels some of the new fizz... reducing the whole effect... 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? If the signal has no distortion, then yes, all that happens is you get a signal that matches what the pickup gets from the strings (except a small phase difference), and so you cannot hear this direct coupling interference - it is masked. Thats what I've been talking about since I designed my second AGC - the goal was to use that effect, and it works - you've heard the clips. 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... If you think about this you will realise that the system would settle in a state where it was right on the threshold, and it would start switching that switch at a hefty frequency - most likely causing horrible noise, bad oscillations, shortening the life of the switch etc. cheers Col Link to comment Share on other sites More sharing options...
col Posted February 24, 2008 Report Share Posted February 24, 2008 (edited) I don't think that the phase issue is a big problem. It can be split up into 3 areas: pickup, driver and electronics. For the driver I allready gave you a way to calculate phase shifting. Here is my document to calculate the phase shift of the driver. For the pickup you could do the same calculations, but it's a waste of time. Any decent pickup well extends the range of 1100 Hz. Unless you have some kind of superdistortion very ugly metal humbucker. What electronics concerns, if the signal is only amplified without any toneshaping (eq) there won't be much phase shift. About Helmholtz: I found this interesting link. I think this and also this links show the real problem to solve to achieve fundamentals below the 12th fret. The java applet shows that the fundamental is around 10 dB weaker than the 3rd harmonic (pickup at some 2" from bridge). So the fundamental cannot compete with the 3rd. Hmm, I think you're still not getting the point of what I've been talking about. I understand that Helmholtz motion is not some magic thing that shows us a brand new insight into the physics of the motion of the string, however what it does do is let us see intuitively what would otherwise require quite a bit of analysis and maths. Those links you posted are interesting particularly the first. The guy states and shows that "A string which is fixed at both ends will exhibit strong vibrational response only at the resonance frequencies" and that the equation that he presents of the string at resonance represents a standing wave... All well and good - what this does not take into account is that the excitation of the string due to picking/plucking at some position near the bridge introduces a bunch of 'other' frequencies that are related to each other physically (helmholtz kink). These will disappear as the "strong vibrational response only at the resonance frequencies" takes over, at which point most of the characteristic guitar sound is also gone. My understanding is that my current sustainer works well. BUT rather than prolonging the nice characteristic guitar tone, it actually hastens the damping of that and the tendency of the string to revert to a simple standing wave. The most important phase shift I'm talking about in relation to this is not the driver circuit or pickups electrical phase shift, it is the shift caused by the physical positioning of the driver with respect to the pickup. I am fully aware that the mechanism that I have described in the past in relation to Helmholtz Motion is also explainable in terms of a combination of superimposed standing waves, and the momentum of the physical string. It seems to me that no-one else hes yet taken enough time to think about what I'm talking about (or I'm completely wrong, but bear with me for now). I think that one possible reason for the misunderstanding is that there is a time during the development of the vibration of the string after the initial excitation where the energy imparted into the string (kink) is opposing the natural system of resonant standing waves as described in those pages you linked to. It is this effect that is much easier to consider by thinking about a kink in the string moving in a parabolic motion rather than in term of standing waves. This is a relatively short period after which most of the character of the note is gone. I want a sustainer that prolongs this effect rather than one that actively shortens it (my existing system). Achieving this goal (and the extent to which it is achievable) is all tied up with the electrical phase of the total system, and the phase shift caused by the physical positions of the driver and pickup. I'll try to write another explanation of how I think the 'kink' / gap combination causes active damping and how we might go about minimizing this - the compromises there might be etc.... and why a square wave may be a better drive waveform (fizz issues aside). If it wasn't for this perceived issue, there would be no point in me actively working on this project as my sustainer has worked well for a long time - strong sustain, clear fundamentals on all open strings, no fuzz/fizz, even response, various harmonic modes. BUT there is something sterile about the sound, and I feel that at least some of that is that it hastens the change from complex guitar tone to simple/boring sine like standing wave through this damping effect... Enough for now anyway - but please think some more about this rather than dismissing it. cheers Col Edited February 24, 2008 by col Link to comment Share on other sites More sharing options...
col Posted February 24, 2008 Report Share Posted February 24, 2008 Hmm, it might not be as easy as I'd hoped to counteract the cancellation caused by driver/pickup positioning. I was using the simpler bowed string model of the string vibration - the guitar string seems to have two kinks that move in opposite directions from the picking point... this would mean that its not possible to adjust the phase electrically to counteract the spacial offset. The only way to do it would be to have the pickup and driver in exactly the same position. Thats something I've thought about a lot in the past, but still no idea as to how to achieve it. gonna work on an animation to help visualize - all the available ones pluck the string dead centre which is not realistic for guitar. Col Link to comment Share on other sites More sharing options...
psw Posted February 24, 2008 Author Report Share Posted February 24, 2008 If it wasn't for this perceived issue, there would be no point in me actively working on this project as my sustainer has worked well for a long time - strong sustain, clear fundamentals on all open strings, no fuzz/fizz, even response, various harmonic modes. BUT there is something sterile about the sound, and I feel that at least some of that is that it hastens the change from complex guitar tone to simple/boring sine like standing wave through this damping effect... Same here...mine is a little better than the sustainiac in that regard having at even moderate gains more dynamics and touch sensitivity even as it does, perhaps a little distortion with it when it does. The sustainiac does have that sterile kind of character, it is very good, but I believe that this thing could do a little more. Perhaps the sustainiac would sound a bit more like mine if it was allowed to push a little more, I guess it is up to the installer a little and one guitar is perhaps not the best juudge of these things. The other important difference is that I wish to incorporate the device into a fully functioning guitar, neck pickup and all. That means if it uses a stand alone driver it will need to move over, tackling switching complexities and influences of "secondary coil effects", a design that allows mounting and fitting all the electronics, switches and batteries into a guitar with all it's other stuff still in there and to work just as well as in stand alone testing. There are also effect and performance potentials yet to be explored. With all this, redesigning the drivers continually has not yielded any real answers and most seem content to use a single pickup guitar/test bed for research, development and use. Each time round, it becomes a bit more out of phase with the fresh fizz being created, so after some number of iterations, there is cancellation - both of some of the new fizz, and some of the old fizz... this prevents it from snowballing into squeal... it also accounts for the effect where the fizz is loud for a short while then magically clears up quite a bit. The 'old' fizz cancels some of the new fizz... reducing the whole effect... QUOTE(psw @ Feb 24 2008, 01:11 AM) * 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. I'm don't understand why that would be the case? Well...because you describe the fizz above as a cycle as I would predict, but I don't experience it in this way, so perhaps my "distortion" is different.... _____________ I don't want to encourage glossing over your points so I will try and engage a little more in this...we are of a similar mind in desiring a more characterful "dynamic" sound... I think that one possible reason for the misunderstanding is that there is a time during the development of the vibration of the string after the initial excitation where the energy imparted into the string (kink) is opposing the natural system of resonant standing waves as described in those pages you linked to. It is this effect that is much easier to consider by thinking about a kink in the string moving in a parabolic motion rather than in term of standing waves. This is a relatively short period after which most of the character of the note is gone. I want a sustainer that prolongs this effect rather than one that actively shortens it (my existing system). Achieving this goal (and the extent to which it is achievable) is all tied up with the electrical phase of the total system, and the phase shift caused by the physical positions of the driver and pickup. A fair way back, I described the act of picking a strings, even the way in which a string is picked as "distortion" the vibration of the string. Unfortunately my english use in this context implied a clipping, but in fact I was trying to say a similar thing, the plucking it would seem to create effects such as the Helmholtz Motion. I am fully aware that the mechanism that I have described in the past in relation to Helmholtz Motion is also explainable in terms of a combination of superimposed standing waves, and the momentum of the physical string. It seems to me that no-one else hes yet taken enough time to think about what I'm talking about (or I'm completely wrong, but bear with me for now). Plucking of the string would seem to set up some different wave patterns initially, normally the note settles down, but then it also fades away as it decays. By sustaining the string and exciting it as we do (not picking it) the result is a continuation, or perhaps even a dampening down of these initial characteristics into these more sterile sounding vibrations. One way of adding character as the note is sustained is my approach to allow the thing to drive a little harder and so creating it's own "distorting effect" on the vibration of the string. Unfortunately, to some extent driving it hard like this produces actual clipping or fizz distortions into the signal. Another is to allow the string to be driven so that it "evolves" slowly, or hangs on the brink of peeling off into it's harmonics. This is also an effect that I love and while the sustainiac can "dial in" harmonics it tries to suppress this effect it would seem (there were a few occasional spots where it wanted to I noticed on the high e around the twelfth fret)...again, perhaps a different guitar setup would have had a different effect. These are the kinds of things I am working on now with fairly conventional driver designs. Perhaps to get more of what you are seeking you need to look at very radical departures in the way in which the driver excites or continues to excite the strings. I did try a range of different approaches, one was a design that I pursued for a long time that aimed to move the strings more from side to side rather than the vaguely up and down motion of conventional perpendicular coils...It can work, but not in my format and a lot of work...whether this holds more promise for what you are seeking I don't know. Another was a very radical approach...not sure if this would ever be completely practical given pickup placements and such. Long term readers may remember me trying to pursue a scheme where the driver was incorporated into the bridge. One "mad" scheme that I tested was to create a coil around a sleeve through which the string passed through (I used a steel rivet), a tiny but powerful neodymium magnet sat on either side of the string just after the bridge, one north, the other side south. The idea was that the string would be magnetized alternatively and that this pulsing signal would then be attracted to one or other of the magnets creating a side to side or circular motion and that it would create Helmholtz Motion like effects up and down the string (of course in the test guitar, it only had a neck pickup...) perhaps... Mad as this may sound, it did create vibrations in the strings... Another thing I didn't really explore but may have potential is a longitudinal drive, where the coil acts along the string length...if that makes sense. A lot of these ideas stemmed from the HEX technology with the small and individual drivers allowing these possibilities, however impractical. Also, it has been assumed that the driver is set in the neck position because it can operate on a part of the string where there is greater "throw" or movement of the string. However, the fact that my driver will create very strong sustain on the 22nd fret right up to the driver itself shows that more than adequate sustain can be created right up to the end point of the string (in this case the "nut" effectively). Acoustic sustainer experiments also hold some ideas. A "power-slide" can be created with a transducer (weighted speaker coil with cone remove) the vibration of which creates an extremely powerful sustain (don't let it get too close to the pickups though...squeal!!!!). When I was working in this area, I wanted to create a device that would physically vibrate the floating bridge of a stratocaster...however, interference with the pickups above was a problem, as was the physical delays in the mechanics of moving such hardware in time with the strings. I even tride to use under saddle piezo type vibrators to excite the bridge saddles (was in no way successful). In the end, I did resign to a more conventional approach for various reasons, but perhaps there is more to these alternative ideas yet if you feel inclined to go down that road. There were other advantages being sought too. The idea of using any pickup combination and bypassing a lot of the switching problems, the negating of the effect action has on the strings (as the string is pushed closer to the driver) by placing the device close to the bridge. Perhaps you would consider experimenting with an acoustic type sustainer like the sustainiac model c and see if this produces more of the sound you are after (vibrating the whole guitar from the peg head). To me, while I agree with your ambitions, a guitar note is an evolving tone and so, prolonging it leaves at best only the more boring tail of the note, at worse suppresses character into an even sterile sound. My feeling is that, once the string is artificially sustained, it is no longer a natural vibration, but that does not mean that it needs to be "boring" or sterile, a digital sample and hold replay of the beginning of the note would be equally as boring, though possible of course if prolonged sustain were the only ambition. I think that some imagination is required to envision what it is you want the note to do as it is sustained...and what that might sound like. What I seek and have found to some extent is more dynamics and effects like harmonic breaking as a note sustains longer. This is the effect of "expressiveness" that I refer to where notes don't always build to a crescendo of maximum sustain and that pick attack and strength can influence the evolution of the note. Harder to control, but more rewarding in the hands of a skilled player. A lot more interesting that simply having the ability to hold a note for ever, but to be able to manipulate those notes. Vibrato and the trem can also have a dynamic effect on such notes too, opening up more techniques and control in the players hands. These are the qualities that, for all the remarkable achievements the sustainiac have made lack (given that we have not really matched them) and where areas of exploration still reside. That, and the technical problems of installation and making this more widely available so that I can here it in use by skilled players, is what keeps me at it! pete Link to comment Share on other sites More sharing options...
col Posted February 25, 2008 Report Share Posted February 25, 2008 (edited) Here's an interesting page in the Agilent student resources. (you don't need the images this text refers to, but you can see them at the link... emphasis is added by me) The top shape represents the string plucked near the bridge. The resultant sound is harsh. The next two shapes show the string plucked over the sound hole and at the midpoint, respectively. The lower shape is the natural resonant shape of the string, after it has settled to “steady state” vibration. In this state, it makes a sound that is closer to a pure sine wave. You can see that plucking the string in the center would make it much easier and faster for the string to assume its steady state shape. Each of these positions creates a different “voice” on the guitar. By mounting more than one pickup on the guitar, electric guitars take advantage of the fact that the string vibrations vary with position along the string. Engineering and the Guitar Part 5 Figure 2 When the string is plucked in its center, the string tends to vibrate in simple harmonic motion. But when plucked near one end of the string, in addition to vibrating back and forth, the string has a traveling wave that moves along its length. When this transverse wave finally settles down, the string sounds the way it does when you pluck it at the center. There is another interesting phenomenon that we haven't yet considered, at least from the point of view of understanding its impact and that is the polarization of the strings vibration.. ie it vibrates both up and down and side to side. One discussion I found suggests that is starts with plenty of up and down, then theres a point where it switches to mostly side to side - during this switch, there is a slight dip in the volume. I wonder if this is what is causing the poor 'release' times of my system. The dip in volume causes the AGC to start driving the string, but the string is 'switching' to side-to-side motion, so the driver has to battle this and pull it back to up and down motion causing a further drop in amplitude, and then and even more obvious swell as the sustain finally kicks in. (I make it sound more extreme than it is - this effect is not a show stopper, but I would rather it wasn't there at all). Maybe another reason to go for a brick wall limiter rather than a full on 'dynamic range inverter'. cheers Col Edited February 25, 2008 by col Link to comment Share on other sites More sharing options...
psw Posted February 25, 2008 Author Report Share Posted February 25, 2008 Well...that is interesting stuff, but only supports what I said originally, the sticking of the string causes a distortion (check out the images...things like this... eventually settle down to something like this... So...the question is, what do you want an "artificially" sustained note to do over the length of it's duration? After the initial distortion to the sound on exciting the string, it settles down...and fades away. With the sustainer, the natural inclination is for the note to continue to sustain in a sine like way (although I think it is more to it than this). I think it is up to us to decide what we want the note to do once it settles down. I agree with you, you want something more expressive than just infinite sustain...the novelty soon wears off and this is a deficiency with sustainers in general I suspect that makes them less attractive than they might be. A note that over prolonged sustain gradually evolves to a harmonic, or notes that don't always rise to a maximum drive level is a good aim. A note that starts clean but rises to include some distortion I think is acceptable too. It all depends on what you want it to do. I am enjoying some of the polyphonic effects possible...mine has quite good even sustain of notes in a chord...it seems to favor the higher strings unusually (it may be the way I set up pickup and driver heights), so it has a nice evolution of individual notes in the chord. I need to get a little more range of gain, I have a window set by a trim pot on the circuit, this can be adjusted to just below squealing for a very dynamic and harmonic laden sound...unfortunately if you do this you cant get the gain low enough...even adjusting it the other way, you loose some of this upper limit, but even then the LM386 is putting out a little too much power, it could be less even and still produce infinite sustain and be cleaner. Bodes well for battery consumption, but then how it would work with a less powerful bridge pickup if I was to add resistance to the input to tone it down. -------------- I continually take the test guitar apart and still incredibly frustrated with difficulties with the switching. Adding the mioddle pickup made things even worse, before I just got a bit of switch noise...hmmm. The, in trying to fix it, the driver coil finally failed after months of misuse (it is not designed to be taken on and off repeatedly) and so, earlier it shorted to the poles which I fixed, but then the leads broke at the critical point at where they turn over the bobbin and so is destroyed. I found a spare and fitted it to another pickup...working really well again, but only with the one pickup. I may have a few more ideas, but it is incredibly frustrating that it works well but only in this form. Before I take it apart again, I will try and record it while it is still working. __________ pete Link to comment Share on other sites More sharing options...
Fresh Fizz Posted February 25, 2008 Report Share Posted February 25, 2008 The most important phase shift I'm talking about in relation to this is not the driver circuit or pickups electrical phase shift, it is the shift caused by the physical positioning of the driver with respect to the pickup. What you really want/need is a method to convert the pickup signal into driver signal. Something like a computer programme that recalculates per string, per frequency the amplitude and phase shift for the occuring string movement. In fact simulating a pickup that's situated on the driver's position. The best solution would be to have both driver and pickup at the same position. Like Pete has been trying to do. Could it be done with an optical pickup and a magnetic driver? So...the question is, what do you want an "artificially" sustained note to do over the length of it's duration? I think that no matter what you'll allways end up with a sine wave. But it would be nice if it was possible to get a different harmonic by changing the way you pick the string. But in my case it's allways the same, 3rd harmonics low, fundamentals high on the fretboard. And I want 2nd harmonics as well! I would like to rely more on another feedback principle: fingers to ears and vice versa. Stick a volume pedal in between pickup and F/R amp. And decide by hearing when the sustainer device has to be set into action. I tried to get fundamentals below the 12th fret. Therefore I used a fet to boost the low. This way I was able to get fundamentals on my wound strings but it made my plain strings sound even thinner by comparison. And it didn't feel right. When playing on my g-string I felt the wound strings shaking insanely. Anyone knows how the commercial guys get good fundamentals on all positions? Is it eq, all-pass filters or is it their trick of trade? Cheers Fresh Fizz Link to comment Share on other sites More sharing options...
utopian isotope Posted February 25, 2008 Report Share Posted February 25, 2008 (edited) I tried to get fundamentals below the 12th fret. Therefore I used a fet to boost the low. This way I was able to get fundamentals on my wound strings but it made my plain strings sound even thinner by comparison. And it didn't feel right. When playing on my g-string I felt the wound strings shaking insanely. Anyone knows how the commercial guys get good fundamentals on all positions? Is it eq, all-pass filters or is it their trick of trade? Cheers Fresh Fizz Too much low frequency boost there I guess. Problem is that driver excites wound strings more, because they simply contain more iron. So it needs compensation. I assume you don't really want to kill your driver by frying it? In my case, I still have an overpowered sustainer amp, that gives so much juice that driver starts to stink. I'll do my best to avoid that situation by lowering excessive lower strings excitation. (Maybe) easiest way to test this is an eq. ------- Difference is that I'm using only harmonic mode on my tests, and used eq to decrease lower end. Mid and/or high frequencies might need to be increased. I've done all testings with an eq by ear. Eq isn't the final key to feedback heaven, but at least it can give some direction. But remember, every setup is different. I'm currently using only one P-90 at bridge. ---------------- OT: I have a strat also, but it's in pieces. I have to do some serious fret leveling (or is it sanding?) to it, before it's good enough to put together. Would be fascinating to test that, and see what psw is struggling with... Edited February 25, 2008 by utopian isotope Link to comment Share on other sites More sharing options...
col Posted February 25, 2008 Report Share Posted February 25, 2008 (edited) feck - double post Edited February 25, 2008 by col Link to comment Share on other sites More sharing options...
col Posted February 25, 2008 Report Share Posted February 25, 2008 (edited) The most important phase shift I'm talking about in relation to this is not the driver circuit or pickups electrical phase shift, it is the shift caused by the physical positioning of the driver with respect to the pickup. What you really want/need is a method to convert the pickup signal into driver signal. Something like a computer programme that recalculates per string, per frequency the amplitude and phase shift for the occuring string movement. In fact simulating a pickup that's situated on the driver's position. The best solution would be to have both driver and pickup at the same position. Like Pete has been trying to do. Could it be done with an optical pickup and a magnetic driver? I have looked at a few designs for optical pickups, however, I'm not keen on any of them at least in this application - the problem is that to be practical, they really have to be very close to the bridge. Using DSP software is a possibility - certainly not out of the question from a DIY perspective either. The main problem there is that one would need a driver per string, and that the fields from these drivers would interact with each other messing up the separation that you would need to make the thing worthwhile. Driver and pickup in the same position would be ideal - still haven't come up with a viable concept for that yet... A combination of pickup and driver and in the same place, with some very fancy intelligent DSP to seperate the pickup signal form the drive signal seems like the most likely proposition, but thats getting into some very difficult analysis even to just work out if its plausible. What I'm looking at really is to use a better understanding of the motion of the string and the phase of the different parts of the system to make it easier to tailor the system to work the way I want it to... e.g. it should be possible to optimize it so that it works best, or just sounds best at a certain part of the neck... maybe even a switch so that you can choose where the sine like sustain will be, and where the slightly warmer sustain will be.... e.g., we don't want the best response of the system to be on the 6th string above the 10th fret do we ? So...the question is, what do you want an "artificially" sustained note to do over the length of it's duration? I think that no matter what you'll allways end up with a sine wave. But it would be nice if it was possible to get a different harmonic by changing the way you pick the string. You'll certainly end up with something closer to a sine wave pretty quickly if your system is not set up to minimize the damping effect the driver has on all but the fundamental. Two things can help here: use a square wave to driver the string (causes more fizZ); try to do something about the cancellation due phase difference between driver and pickup (might not be possible). There are other possibilites that may work, but with other potential drawbacks. Anyone knows how the commercial guys get good fundamentals on all positions? Is it eq, all-pass filters or is it their trick of trade? One thing that is likely to help is to use a bigger output cap - e.g. try a 470u (oops, I see you're already on more than that :-\) Really I think a lot of it comes down to getting the correct mix of a bunch of different factors - it basically boils down to tweaking the frequency response of driver, circuit and pickup in both amplitude and phase. Understanding these factors will make this job much easier. The other thing that seems to help is AGC - probably due to some physical factor relating to amplitude and phase... maybe if the drive on the open 1st string is not strong enough, the pull of the permanent magnets can cause harmonics to win over the fundamental... I guess there are different possibilities. ----------------------------------------------------------------- Here are some questions for you guys (for Fresh Fizz really): I understand and can calculate the electrical phase shift at different frequencies caused by an inductor (including the effect of its internal resistance). e.g. for a 1mH inductor with a resistance of 8ohms, at 300Hz the current lags the voltage by 13.2º for a 4mH inductor with a resistance of 4ohms, at 300Hz the current lags the voltage by 62.0º for a pickup with a 6K resistance and an inductance of 6H (ballpark guesses), the lag at 300Hz is also ~62º if its inductance was 3H, the phase would instead be 43.5º I got some specs for real pickups - this one has a fairly average phase response: ( i looked at all sorts) 'DiMarzio dual sound' resistance = 13.68k inductance = 6.4H here are the shifts at different frequencies from the guitars range (fundamentals only) 13.2º @ 80Hz.... 42.5º @ 300Hz... 61.3º @ 600Hz... 74.2º @ 1200Hz Question is: does the field generated by the inductor (thats the important part for us obviously) have the same phase lag as the current ? In other words does the internal resistance of the inductor effect the phase of the field? If it does (and I'm assuming that it does), then the variability of phase response possible with just small changes to our driver designs (and installed pickups) is indeed a significant factor. (Mostly this is for Fresh Fizz because of his assertion that "For the pickup you could do the same calculations, but it's a waste of time. Any decent pickup well extends the range of 1100 Hz." - I don't see how these results could be considered a waste of time unless they don't effect the phase of the magnetic field.) cheers Col Edited February 25, 2008 by col Link to comment Share on other sites More sharing options...
psw Posted February 25, 2008 Author Report Share Posted February 25, 2008 PAGE 7 WAS A GOOD PLACE AS i HAPPENED TO RECALL...THIS WAS A TIME WHEN I WAS DOING A LOT MORE PATENT SEARCHING... LINKS It’s been very neglectful and selfish of me to focus on my experiments and theories without referencing the basis of them. Especially since I promised links, etc. and haven’t posted any! – now that I’ve got a little bit of a handle on the controls – here goes... PATENTS For those interested but not checked them out yet patents and the secrets within can be accessed free at USPTO Patent Search You will need to download a viewer to see the actual original documents with diagrams The “referenced by” and “cited by” links will automatically send you to related patents so you can check out the origins of ideas and where they are going – much fun! Warning – you may soon start thinking in patent-speak and, like me, use a thousand words and still confuse the hell out of everybody!!!!! Now to sustainers... Here is a great little article on Michael Brooks Infinite Guitar and it’s heritage to the Sustainiac, Fernandes and Floyd Rose systems and a little of the secret workings of his! Infinite Guitar Article Ok, now... For Lovekraft, Ansil, et. al.... Perhaps the best for explaining the problem and lengths gone to by some to solving the phase shift dilemma (Heet’s Ebow not withstanding) is contained in Floyd Rose’s 1995 patent 5,233,123 Floyd Rose Sustainer Patent 1995 Because of the length of these documents I’ll spend the time to quote from them so that everybody need not wade through them as I did...so...from Floyd Rose page 7 = (FR7) Regarding phase shifts (FR7) “The force applied by drive means employing an inductive coil tends to lag behind the drive signal or voltage applied to the coil. Moreover, this lag increases with the frequency of the signal.” Details of the complex circuitry and formulas for lag and lead compensating (FR11-17) Ansil – (FR18) describes an alternative means by using a phototransistor which may be of interest to you. The phase shift circuitry involves (FR21) “In operation, waveform squarer, frequency to voltage converter and amplifier cooperate to provide a signal voltage which increases directly with the predominant frequency of the pickup.” Basically the f to v converter seems to switch in various capacitors with frequency “Thus, as the capacitance of the drive decreases, the component of the drive force at a given frequency will have less lag (more lead)” Another important patent is from Osbourne and Hoover 1999 (=OH) 5,932,827 This seems to relate to the Sustainiac Stealth System Sustainiac Stealth Website Osbourne and Hoover Sustainiac Patent 1999 This patent utilizes means to eliminate feedback (EMI shielding) and a means to conserve battery life. There is a description here of adverse effects of prior drivers on the tone of the guitar (OH17-18) For more on this subject, I found this discussion: Adverse Tone Effect Discussion Anyway, back to the phase shifts...(OH18) “Means are also provided for enabling the driver to accept the phase inverted drive signal and provide a drive force that is generally in-phase with the vibration of the string” On energy conservation (OH20) “Provides a non-linear switching amplifier to decrease wasted energy” On multi-string (one driver for all six) vs. single string (six individual drivers)...(OH26) “Such an arrangement provides an advantage over a multi-string driver with respect to the direct magnetic feedback, but a disadvantage relative to the lateral uniformity of the magnetic field.” On amplitude and frequency compensation (OH43) “Current source amplifier automatically compensates the frequency related amplitude response and phase response of drive current” OK, so there’s a smattering of the current state of play, except for the ubiquitous (just wanted to use that word) Ebow patent Ebow Patent Now, this is a lot to digest I know. I don’t have much experience in electronics (been teaching myself for this project) nor do I have a background in physics or the heavy-duty mathematics that I'm running into. What I hope to do is defeat this with guile, ingenuity, creativity and a lot of luck. ..oh and your contributions ....keep them up Hope this helps further our discussions psw Lovekraft...what can I say...I'm honoured . Don't back down though as you may indeed be the voice of reason! No, don't misunderstand me, I still think the "phase issue" is smoke - but I understand after reading the patents why it worries you. However, this section from the FRS patent makes me think otherwise (and keep in mind that the full fundamental range of a 24-fret guitar in standard tuning is >80Hz to <1400Hz): With straight through circuit 78 engaged, the drive signal is in phase with the pickup signal, and hence the drive force lags behind the string motion by an amount equal to the lag caused by pickup 34 and driver 52. In this mode of operation the efficiency of the sustainer in reinforcing the fundamental vibration of the strings is less than with variable lead network 82 engaged. However, this effect is most pronounced at relatively high fundamental frequencies, above about 300 Hz and particularly above 600 Hz. Thus, the sustainer will provide a useful sustain action for relatively low frequency fundamentals when straight through circuit 78 is engaged. Moreover, when the straight through circuit is engaged, the sustainer does not tend to lock in on the frequency of only one string. It sounds like they're simply having to compensate for the inherent lowpass nature of the inductive driver and the fact that a shorter string takes more energy to drive it, but I still think it's a frequency response issue only peripherally related to phase shift. However, after wading through most of both of those patents, I'm convinced that the complicated systems described in each are just hedging their bets. I seriously doubt that either patent holder is implementing all of their "innovations" in the current incarnation of their commercial product - the rest is padding and hedging to make their claims look more innovative and therefore patentable (shades of Randall Smith!!). I'm convinced ( at least until someone proves me wrong) that simple equalization just like that used to compensate a speaker (another inductive transducer) for flat response will more than take care of any problems that may result. Moreover, if you're using a separate driver for each string, you only have to make the response flat over a two octave range, further simplifying the necessary EQ. Digital amplifiers and frequency-dependent phase shift both sound good in marketing literature, but I'm not at all sure they add anything more than mystique to the final product. I would concentrate on gain control/compression and frequency response, designing a driver coil that works best as a driver (ie., don't try to use a pickup-style coil, think more along the lines of a diaphragm tweeter driver), and isolating the driver system electrically and magnetically from the signal path to avoid any timbral interaction. Of course, that's just my opinion - I could be completely wrong. LOVEKRAFT, bless his soul, helped me a lot in the early days of the thread both here and via email towards the end , but like all his post on PG, we can still gain a lot from his thoughts. These two posts may help with the patents and Lovecraft's observations and discussions at this time lead me towards seeking better drivers that don't require the electronic compensation typically featured in recent sustainer circuit documents. It is dangerous to go back, I get to reading and the next thing you know, I am back to the beginning...and in many ways after 4 years, we still are!!! Frustrating... ---------------- There are lots and lots of related patents, one back to the 1890's for a valve driven sustainer piano...some interesting stuff, if doing patents, make sure you download a viewer so you can see the images and use the referenced and referenced by hyper-link function to get to related patents past and present. Don't get too hung up on them, they are all very convoluted and sometimes it would seem purposely misleading. ----------------- In their descriptions of phase correction methods and reasons for it, they consistently refer to the difficulty in driving the high strings. Early on, I too had such problems but with more recent designs including the one I use now, there is no difficulty (except that "harmonic mode" does not work at all. ------------------ I assume you don't really want to kill your driver by frying it? In my case, I still have an overpowered sustainer amp, that gives so much juice that driver starts to stink. I really think you need to change your approach. It would seem that you are using high power to compensate (not only perhaps 5+ times the wattage as me and col and others, but you are running it off mains power so current (although voltage has been compensated for) is fairly extreme! Since this morning, I am resurfacing the past...from the very first post... Many years ago I wound a crude coil and ran the guitar output to both my amp and a trashed hi fi amp. The output of this went directly to the coil placed beneath the strings. It worked!!!!!!!!!!!! However some notes better than others, but still it worked!!!!!!!!!!! Only one drawback. Within minutes the coil heated up like a bar radiator and proceded to melt the electrical tape holding it together. The strings really heated up and the whole thing threatend to catch on fire! Still it worked!!!!!! I've got some recordings somewhere to prove it. Would make a great stage act! One of the first things that needs to be realized is that the forces need to be balanced...brute force is not going to produce the best results. If the driver is efficient, my mantra throughout and encouraged by LK, is efficient enough (hence terms like "speed") then high power and frequency compensation does not become so much of an issue. At the moment for instance I am reporting still too much power from a LM386 on minimum gain and only a buffer in front! More power for instance is only going to create more EMI (unless it is used to run at a low level to create clean headroom perhaps). ------------- What you really want/need is a method to convert the pickup signal into driver signal. Something like a computer programme that recalculates per string, per frequency the amplitude and phase shift for the occuring string movement. This is kind of what the sustainiac, fernandes and floyd rose patents describe (among others), not a computer, but in the case of rose, an op amp used to create a frequency to voltage signal to trigger phase compensation networks. They all seem to relate however to high frequency response, no mention of distortion or fizz effects related to phase that I recall. However, bear also on mind LK's thoughts posted above and my subsequent work where drivers have been created that more than adequately cope with high strings with no compensation... ---------------- I think that a distorted clipped signal is going to lift the harmonics and is the "flaw" (or is it a feature in this approach. I too get such effects at high gain, but then at these gains the little LM386 is running well into overdrive, simulating your diode approach. ---------------- I think that no matter what you'll always end up with a sine wave. But it would be nice if it was possible to get a different harmonic by changing the way you pick the string. But in my case it's always the same, 3rd harmonics low, fundamentals high on the fretboard. And I want 2nd harmonics as well! I would like to rely more on another feedback principle: fingers to ears and vice versa. Stick a volume pedal in between pickup and F/R amp. And decide by hearing when the sustainer device has to be set into action. Now we are on a similar page... I always wanted to develop a control that adds this device as easily and intuitively as a trem is integrated into the guitar for pitch shift. This is one of the reasons that silent switching is so important to me, I want to be able to switch it on and off on the fly. A small push-push button always had some appeal for this. The volume pedal idea, not so much and very difficult to do in practice, given that by necessity it is an on-board device (though many have desired an off board approach). You should be able to get the desired adjustability of responses from a single control (I appear to have) and having this on the guitar is better IMHO than a volume pedal, etc. What I am getting is very much as you desire. On low level gains, I am getting a pretty clear sound, nice chord sustain and a fairly even response. Low strings ring at their fundamentals for about as long as they would without the device, but slowly morph to a harmonic (the low e to b above for instance) after this time. So, it plays fundamentals but on very low notes these are not sustained, their harmonics are...which is a really cool effect actually. At higher gains, this response is much faster. At these gains at the expense of some non-fizz sounding distortion, you get very touch sensitive harmonics. A pick harmonic will typically continue to sustain as one, a sounding harmonic slid from fret to fret, brings them all out as harmonics in the same range. Tapping, instead of picking the strings brings out harmonics too. Using such gains and techniques I get very strong harmonics all the way up to the 22nd fret high e (a little piercing) and even can get "evolving harmonics" where after prolonged sustain with high gain, the harmonics are revealed. You don't want to go too high, these notes are already piercing, on high notes, the harmonics can be octaves above the sounded note, the result is difficult for most guitar amps to amplify and hard for our ears to hear...your likely to really annoy local dogs!!! Harmonics are great but be careful what you wish for, it sounds more like a whistle than a sine wave effect and can be a little painful! -------------- Both f-fizz and UI are using methods similar to those by me way back when (over 15 years now I suspect) and described in the first post...at least to some degree. I don't know if yours does this also, but my early experience also created massive tuning problems, the driver would actually bend the strings out of tune in operation! Eventually I predict that you will find this approach to be less than satisfactory and use this experience to make better drivers and amps to drive them, possibly draw on them for producing effects like these harmonics and such. Nothing is really wasted. On the clipped drive signal, LK used to advocate that, and then things changed, I did not get too far and it didn't seem to improve things too much. It is not an unreasonable idea to pursue...I am not simply "knocking it"...hope you understand. -------------- I have a strat also, but it's in pieces. I have to do some serious fret leveling (or is it sanding?) to it, before it's good enough to put together. Would be fascinating to test that, and see what psw is struggling with... Here again is the guitar I presently use... Some strats make an excellent platform for experimenting with. I have now set this one up so it plays quite nicely, you can use the trem to lossen the strings to make pickup removal a lot easier. They are screwed to plywood and thes are stuck on with double sided foam tape. I use screws into the guitar to allow these mounting boards to be raised and lowered and the pickups are screwed or sometimes simply taped onto these. Sorry about the UFO approved focus, I don't know what happened there... You can see the little circuit sticking out (black taped with trim pot and lots of color coded wires) handing out below the control mounting plate. The driver is hidden below the neck pickups cover, you can see a red wire taped to the guitar so it doesn't get knocked about too much...obviously not enough as this kind of use eventually destroyed it...hehehe I got a pretty good trem action by changing to two springs on the outside holes and screwing them all the way tight, this left plenty of room for a 9 volt battery that is in a holder behind the guitar and so provides easy access (in some experiments, battery removal is the on off switch!) It constantly changes...now it has three pickups, the neck pickup is now white and a different model, and the knobs are now black since connecting a functional master tone...go figure!!! I have also returned to a typical jap-strat double pole blade switch for pickup selection. Such a guitar and set up is the ideal way to practically test things, theory is good and important but I have found in practical work that trying most ideas outside of a real instrument has severe limitations. Similarly, this thing is working very well at the moment...but only with one pickup connected. However, if your aim is to use multiple pickups, then you would be very wrong to assume that this will be an easy or straight forward task. Also, if your high powered clipping eq preamped systems running off mains power supply is not performing properly with one pickup, how do you expect it to cope with the added complexity of extra pickups, their magnets and coils and the whole switching thing. I'd love for people to get into this aspect of the project as I feel very alone in this pursuit. I'm a little bemused that I seem to be the only one who is seeking to do this at the moment...do you guys only ever use the one pickup or something in playing the guitar? It used to be a major concern of people here that the device only works with the bridge pickup!!! It is still the first question people/players ask me when they hear about the device or see it...some even go so far as to say; "well you know, if it only works with the one pickup, it's not much good is it"... At the moment I am still working towards dpdt passive switching and there seems to be no end of schemes for doing this, one way or another...but none have completely worked. It is very much like a logic puzzle and would suit someone good at that, but it is so easy to overlook things. With the middle pickup for instance, position 4 would often secretly connect with the bridge creating squeal. Then there is the whole issue of switching noise even if you do find a way of doing it, and also now the control of secondary coil effects, connecting loads and such...all very frustrating work. -------------------- I don't think that you could expect to do this with the kind of technology you are running at the moment though I would love the company. Clearly you will need to look into smaller amps and more efficient drivers to even attempt it. However, it is not beyond your means. Most have had to make quite a few drivers to get the quality right for instance...I have had to make a hundred I'd imagine, not all ideas can be proved to have "failed" if quality is poor. It reminds me that I recently heard that people have now been able to light a sixty watt globe, wirelessly. These were ideas tesla proposed years back, but were shown not to be practical or functional to any great extent. Now it seems, with advancing technology, it is possible! And what technology are they using...resonant coils, just like us...so you never know what is possible... pete Link to comment Share on other sites More sharing options...
psw Posted February 26, 2008 Author Report Share Posted February 26, 2008 I have uploaded a bunch of songs but soundclick needs to clear the page before it is active...grrr These sites are so frustrating, if only it was as easy as photobucket. All pretty scratch stuff and noodling, played directly into the soundcard with either a bypassed digital effect box or with various different sounds...hopefully it will demonstrate a little of where mine is at and you can tell me about the fizz and stuff and compare it to your own. I am sure everyones is different. Playing without any amp or sim into a card is not a good sound, but this is the only way really try and tell about things like fizz and stuff...however it loads things down a little and so the amp sim versions are not only louder but more reflective of it's true sound. Anyway...may take a short while to be up and running so you will be able to hear for yourself... pete Link to comment Share on other sites More sharing options...
Fresh Fizz Posted February 26, 2008 Report Share Posted February 26, 2008 To Col or a pickup with a 6K resistance and an inductance of 6H (ballpark guesses), the lag at 300Hz is also ~62º if its inductance was 3H, the phase would instead be 43.5º I got some specs for real pickups - this one has a fairly average phase response: ( i looked at all sorts) 'DiMarzio dual sound' resistance = 13.68k inductance = 6.4H here are the shifts at different frequencies from the guitars range (fundamentals only) 13.2º @ 80Hz.... 42.5º @ 300Hz... 61.3º @ 600Hz... 74.2º @ 1200Hz It's nice to see that somebody finally took interest in my phase shift "thing". (For me it's only a tool, a test to perform after having constructed a driver. There could be a lot of other things wrong with the driver but not it's electrical properties.) What is important to realize is that with the guitar pickup it's not about power but voltage amplification. For the most efficient power transfer the load that's been connected up to the pickup would have to be equal to the pickup's impedance. But in case of voltage amplification we can afford to keep the current low. Which means the pickup sees a high impedance as load. To do the calculations right you have to take this load in series with the dc coil resistance of the pickup. If you do the calculations now you'll see that there is hardly any phase shifting. You undoubtly know what happens if you connect your guitar to a low impedance amplifier circuit. You loose all the highs. You could look at it from a power perspective, lots of phase shift which means that a lot of the energy is backfired to the pickup, or from a voltage perspective, voltage attenuation because of high reactance of the pickups coil and low input impedance of amp. You'll certainly end up with something closer to a sine wave pretty quickly if your system is not set up to minimize the damping effect the driver has on all but the fundamental. Not necessarily the fundamental, it could be a harmonic. It's more a survival of the fittest, there allways seems to be one heavy favorite. It would be nice if we could create some sort of bi-state where two frequencies were equally ...favorite (?). Would two agc's or two overdrives in parallel with separate eq be a possible way of achieving this? to Utopian Isotope (in dutch it's even a greater word play: utopische isotoop) I assume you don't really want to kill your driver by frying it? In my case, I still have an overpowered sustainer amp, that gives so much juice that driver starts to stink. Because I overdrive a fet I know exactly what it's maximum signal is. That signal that's passed to my power IC is attenuated in such way that the IC never is overdriven. Meaning my IC doesn't produce distortion and never goes over the limit. (also been checked on oscilloscope). My device produces a lot of distortion and power but so far that hasn't harmed my driver. Doing this way it's possible to take the highs out of the distorted signal before the power IC. If the IC gets overdriven there is no way to do this. For some reason my pickup with it's ceramic magnet puts a lot of emphasis on higher harmonics especially on the plain strings. Or maybe it's the maple neck. Too bad... Greetings to you all Fresh Fizz Link to comment Share on other sites More sharing options...
Fresh Fizz Posted February 26, 2008 Report Share Posted February 26, 2008 For more on this subject, I found this discussion: Adverse Tone Effect Discussion Fortunately this is not something I have to deal with. Apart from the fizz the sustainer device doesn't seem to change my tone. What I am getting is very much as you desire. On low level gains, I am getting a pretty clear sound, nice chord sustain and a fairly even response. Low strings ring at their fundamentals for about as long as they would without the device, but slowly morph to a harmonic (the low e to b above for instance) after this time. So, it plays fundamentals but on very low notes these are not sustained, their harmonics are...which is a really cool effect actually. At higher gains, this response is much faster. At these gains at the expense of some non-fizz sounding distortion, you get very touch sensitive harmonics. A pick harmonic will typically continue to sustain as one, a sounding harmonic slid from fret to fret, brings them all out as harmonics in the same range. Tapping, instead of picking the strings brings out harmonics too. Using such gains and techniques I get very strong harmonics all the way up to the 22nd fret high e (a little piercing) and even can get "evolving harmonics" where after prolonged sustain with high gain, the harmonics are revealed. So you're saying that because of the overdrive I use my device is acting rather nervously, my sustainer is responding too soon, too intense? It's not that it's functioning badly but I want to know if there is any room for improvement. From what I'm reading from you my sustainer could well be a little one dimensional. So I'm waiting for the new soundclips from you. the driver would actually bend the strings out of tune in operation! COOL! Even if I wanted to install another pickup there would be no place to do so. The circuitboard is placed in the mid pickup hole. I want to get more involved in solving problems which are specific to a more complex pickup/switching configuration but from where I am now at the moment it is a luxury problem. And you have to be prepared to answer all kinds of silly questions. OK, one for now, why is the sustainer switch positioned before the pickup selector switch? Who am I to want 2 pickups if he only has one? cheers Fresh Fizz Link to comment Share on other sites More sharing options...
col Posted February 26, 2008 Report Share Posted February 26, 2008 Who am I to want 2 pickups if he only has one? hehe, surely Malcolm would never use a sustainer! As far as getting sustain on the fundamentals. I checked out the phase response of my circuit again (simulation), and from 80Hz to about 300Hz the phase response goes from about 50º to ~8º where it levels off until roughly 3-4KHz. I wonder if the shift in the low notes is helping them by countering the pickup/driver gap on my system? certainly, the area where the fundamentals are most shaky is open 1st string where the phase starts getting close to 0º... One thing that others have often stated is that the 6th string is driven very hard... I have not had that experience, maybe this is why - if 50º is a bit too much 'compensation', then the 6th string would also start to struggle a little (not giving harmonics, just not sustaining as strongly). ------------------------------------------------------------- What you said about the load impedance changing the calculations for the pickups phase response makes total sense. We still have the drivers response to deal with though. I figure that the commercial units spent more resources dealing with compensating the driver phase response because they wanted to use drivers with a higher inductance to give a more efficient performance. I wonder where the line is between gaining efficiency through higher inductance and losing it through losses in the circuitry that compensates for the phase response of the bigger inductance ? Certainly, one of the important factors in the stainiac design is that there are two cores in parallel, so the overall inductance is reduced while the driver can still generate a hefty field (ok, so I'm not being very technical here...) something like this - although I'm probably missing something here: (I used || to denote 'in parallel with') 16ohm || 16ohm gives 8ohm 4mH || 4mH gives 2mH (ignoring magnetic coupling effects - which will be less significant in the bi-lateral driver design anyway) each coil gets half the current flux is directly proportional to current and inductance (Φ = I × L / N) 100mA into an 8ohm 2mH single coil gives 200mFluxThingies 100mA into a dual parallel core with electrical characteristics of 8ohm and 2mH gives 400mFluxThingies so for an electrically equivalent driver, we get a bunch more flux=drive, but with the same phase response(?) Of course, we would need more and wire and a heftier core (ideally laminated) to take full advantage of this. Does this seem correct (apart from the impact of magnetic coupling and number of coil turns lessening the effect)? food for thought anyway cheers Col Link to comment Share on other sites More sharing options...
col Posted February 26, 2008 Report Share Posted February 26, 2008 Here's another possible reason why some folks have trouble with getting a fundamental note - this is particularly for folks who use a stronger drive current. The electro-magnet should never be stronger than the permanent magnet, it should only ever help or hinder the permanent magnet.... If the electromagnet is stronger than the permanent magnet, a 'double pull' will occur causing a harmonic effect. Explanation: When the electromagnet is in phase with the permanent magnet, you get lots of pull. As the two magnets start to oppose each other, the pull on the string reduces. If the electromagnet is too strong for the permanent magnet, then there will also be a part (the peak) of the opposing swing of the wave cycle when the pull on the string increases again. If this is happening, you either need a stronger permanent magnet or a reduced drive current. Col Link to comment Share on other sites More sharing options...
psw Posted February 26, 2008 Author Report Share Posted February 26, 2008 Ok...I am "cleared" Here is the soundclick link... Warmingtone Soundclick Demo Page If all is well...the first two tracks (chord noodles and single note mix) are the guitar straight into the soundcard...occasionally I turn the device on and it is running on a low setting when on. Have just tried to give a mix of high low and chord textures on this... The other ones are with a Korg AX1G on various settings. Beware the increase in volume. Also note that there is background noise, the guitar unshielded and in front of a monitor, there is a bit of a noise gate in the effect, so don't confuse some of that for fizz! Amped 1 is an overdrive sound with echo Sitar, although the simulated effect may be distracting, this kind of sound shoud hide any fizz. Actually I wanted to show how one might approach using effects a little differently in combination with this device. Clean notes and clean chords is a clean amp simulator, unfortunately a little too much compression I suspect...I've not had much experience recording these things. Beware some very high harmonics...careful what you wish for. satchi is what happens when you try and play something you don't really know! I was trying to show the effect with the distortion happening but perhaps the battery was a little low as I couldn't get the harmonics to work as well as they do with a low volume amp in a room. All of these clips were recorded directly into a laptop sound card via the korg to act as a preamp on to Audacity software with no editing or effects and onto a single track. Over time and to illustrate changes, I will add more clips. Basically it gives a rough idea of the way it is working today...performance changes a little with each variation, the most striking whith the secondary coil open (this is shorted) and with different pickups. This is a "Duncan designed" JB copy in the bridge and a no name $5 pickup with compact ceramic magnet below and ultra slim coil fitted above. Previously to this I used a "better" single coil with alnico poles. Obviously I need to cut my nails a little and practice, a lot of notes are produced by simply sliding the fingers along the frets, hammer ons and pull offs giving a legato kind of sound. Notice too the way dynamics can be used...the volume of the note and how it is struck makes a difference as to the length of time of the swell...not everything swells quickly to the max. Anyway...give it a listen, use the timer on the soundclick player or whatever (they can be downloaded if you wish) to point out particular sound concerns and where the "fizz" is, compare it to how your things are working and let me know what issues I need to address. Meanwhile, I will try and make some better clips in time and as changes occur. Oh...I think most of this was with a minimum gain trimmed in, so very low amplification applied, i want to make it lower to address some of that hairy background distortion and I think with thes bridge HB it will make it a little cleaner. As such, it does not really demo the higher gain, harmonically active, though perhaps "fizzier" settings...I will be making some adjustments. you may also hear the thing being turned on and off...if not a click, the normal guitar sound...I wanted to show the difference, as it is a single pickup guitar effectively at the moment, switch noise is not really an issue...as you may hear (or not);-) pete Link to comment Share on other sites More sharing options...
psw Posted February 27, 2008 Author Report Share Posted February 27, 2008 Here's another possible reason why some folks have trouble with getting a fundamental note - this is particularly for folks who use a stronger drive current. The electro-magnet should never be stronger than the permanent magnet, it should only ever help or hinder the permanent magnet.... If the electromagnet is stronger than the permanent magnet, a 'double pull' will occur causing a harmonic effect. Explanation: When the electromagnet is in phase with the permanent magnet, you get lots of pull. As the two magnets start to oppose each other, the pull on the string reduces. If the electromagnet is too strong for the permanent magnet, then there will also be a part (the peak) of the opposing swing of the wave cycle when the pull on the string increases again. If this is happening, you either need a stronger permanent magnet or a reduced drive current. Col This is a very interesting concept and not one I had ever considered, thanks for this col...it provides food for thought, especially with my idea of pursuing a little more power...hmmmm It may explain a little why I get harmonic effects easier on higher gains...still don't understand why the harmonic switch does not work on recent installs...consistently, except on the lowest strings. _________ I was able to get out today and get some materials for a remote power system. I found some nice 4 core shielded cable and a small box...the idea is to use a remote power to a box, run it down the cable with a stereo connection on the guitar end and a stereo lead. I am taking the warning by sustainiac that remote power via a stereo cable is not a viable proposition with their system, so finding this 4 core cable may help. The box will have a mono socket to connect to an amp and a power socket for a regulated supply. I may need to include some smoothing caps or something too...or it might not work as sustaniac suggest due to the amount of power the device draws. I can't come at the idea of having to use two leads for powering the thing and it works well with the battery, but you will go through a few batteries (sustainiac even suggest two!) if you use it a lot. I have found that while consumption is not too bad and a battery will last, performance will suffer a little (mainly from increased distortion or fizz) and harmonics a little less predictable in a reasonably short time and the battery required to recover with a little rest. ___________ Otherwise, I hope that people have been able to check out some of those sound clips... Soundclick warmingtone sustainer demos pete Link to comment Share on other sites More sharing options...
col Posted February 27, 2008 Report Share Posted February 27, 2008 This is a very interesting concept and not one I had ever considered, thanks for this col...it provides food for thought, especially with my idea of pursuing a little more power...hmmmm It may explain a little why I get harmonic effects easier on higher gains...still don't understand why the harmonic switch does not work on recent installs...consistently, except on the lowest strings. I think you would need quite a lot more power for this to be an issue but I'm not completely sure. It's worth keeping in mind anyway. Col Link to comment Share on other sites More sharing options...
Fresh Fizz Posted February 27, 2008 Report Share Posted February 27, 2008 As far as getting sustain on the fundamentals. I checked out the phase response of my circuit again (simulation), and from 80Hz to about 300Hz the phase response goes from about 50º to ~8º where it levels off until roughly 3-4KHz. That 50 degrees phase shift is caused by the output cap. And you probably included the Zobel in your simulation I wonder where the line is between gaining efficiency through higher inductance and losing it through losses in the circuitry that compensates for the phase response of the bigger inductance ? I think that Pete has allready found out by trial and error. Thicker wire -> more turns of copper windings needed to get 8 ohm -> higher inductance. For low and mid frequencies this means a gain in efficiency but the highs stay where the are. It works the same as with overwound pickups. (Loosing the twang.) Here's another possible reason why some folks have trouble with getting a fundamental note - this is particularly for folks who use a stronger drive current. The electro-magnet should never be stronger than the permanent magnet, it should only ever help or hinder the permanent magnet.... If the electromagnet is stronger than the permanent magnet, a 'double pull' will occur causing a harmonic effect. Explanation: When the electromagnet is in phase with the permanent magnet, you get lots of pull. As the two magnets start to oppose each other, the pull on the string reduces. If the electromagnet is too strong for the permanent magnet, then there will also be a part (the peak) of the opposing swing of the wave cycle when the pull on the string increases again. If this is happening, you either need a stronger permanent magnet or a reduced drive current. I use a pretty strong ceramic magnet. But I use rather thinny blades as cores. I wonder whether if the blades get saturated they will produce harmonics. And for that reason: 1. have a tendency to build feedback on a harmonic rather than the fundamental 2. because all of us don't use a core as thick as sustainiac's could this saturation be the cause of fizz? Fresh Fizz Link to comment Share on other sites More sharing options...
col Posted February 27, 2008 Report Share Posted February 27, 2008 As far as getting sustain on the fundamentals. I checked out the phase response of my circuit again (simulation), and from 80Hz to about 300Hz the phase response goes from about 50º to ~8º where it levels off until roughly 3-4KHz. That 50 degrees phase shift is caused by the output cap. And you probably included the Zobel in your simulation No, it isn't. And no I didn't. However, that is a good point - when they are included, the effect is increased somewhat (roughly 100º @ 80Hz - 27º @ 300) making it an even more likely candidate for the symptoms I described (slightly less good sustain on low E, but reasonable fundamentals on all strings) when combined with the pickup/driver gap. I wonder where the line is between gaining efficiency through higher inductance and losing it through losses in the circuitry that compensates for the phase response of the bigger inductance ? I think that Pete has allready found out by trial and error. Thicker wire -> more turns of copper windings needed to get 8 ohm -> higher inductance. For low and mid frequencies this means a gain in efficiency but the highs stay where the are. It works the same as with overwound pickups. (Loosing the twang.) Pete has found the point where there is enough flux from a single coil while keeping the impedance as resistive as possible over the guitars range. It doesn't take into account corrections that can be made using a properly designed zobel network, active filters etc. It doesn't take into account the features of different core materials - It works well for some folks and not for others, some of the 'failures' will be because of not enough flux, and some because of to high an inductance. And what is 'best' for a single coil driver isn't necessarily 'best' for a dual core driver in parallel configuration... I use a pretty strong ceramic magnet. But I use rather thinny blades as cores. I wonder whether if the blades get saturated they will produce harmonics. And for that reason: 1. have a tendency to build feedback on a harmonic rather than the fundamental 2. because all of us don't use a core as thick as sustainiac's could this saturation be the cause of fizz? Yes, good suggestion - Stainiacs system is also prone to fizz, but there are different causes, and core saturation could be causing extra problems for our weedy little cores. I found this at allaboutcircuits.com "Normally, core saturation in a transformer results in distortion of the sinewave shape, and the ferroresonant transformer is no exception. To combat this side effect, ferroresonant transformers have an auxiliary secondary winding paralleled with one or more capacitors, forming a resonant circuit tuned to the power supply frequency. This “tank circuit” serves as a filter to reject harmonics created by the core saturation" Unfortunately, we can't easily create a tank circuit because we have a wide frequency band to deal with. And even if we could with some sort of dynamic capacitor circuitry, it would kill the desirable harmonics in our drive signal. So maybe a chunkier core would help prevent some of the fizz. Of course, then we have to seriously re-consider the effects of eddy currents and probably go for a laminated core. And also look at the effects of a bigger core on the inductance and therefor reactance vs resistance of the driver. cheers Col Link to comment Share on other sites More sharing options...
Fresh Fizz Posted February 27, 2008 Report Share Posted February 27, 2008 Very nice samples Pete. Your sustainer device sounds definately more refined than mine. Did you use one setting per sample or have you've been adjusting settings while playing? To me it seems that you don't need more compression or output level there is more than enough feedback. And those tapped notes seem to go into feedback with ease. Maybe your driver is more efficient than mine. Or a compressed signal is more obedient than a distorted one. I presume that you were using fundamental mode all the time. The strength of using agc is that it gives you a classy sound. But to me it seems that the fizz is more noticable when it occurs. With overdrive there is allways some background nasty-ness but it sounds more creamy. I only need to find a way to make my sustainer not to react so aggressively right after the attack. Could you perhaps make a sample of a problem area of mine? A single G note 3rd fret on high e-string (on my guitar I get a weak, fragile 3rd) I've thought about your switching troubles. How about this one (what's missing) ? Fresh Fizz Link to comment Share on other sites More sharing options...
col Posted February 27, 2008 Report Share Posted February 27, 2008 (edited) Fresh Fizz, I've been doing some simulation of the Fetzer Ruby, and the phase and amplitude responses are terrible. Are you using the basic F/R, or is it modified ? Using this circuit could easily be the cause of your problems with the lower notes. If you can post a diagram of the circuit and settings you are using (assuming they are non-standard), FET biasing voltage, pot settings etc., I'll check them out and see what the response curves are like. The Fetzer Ruby at best (LM386 input attenuator an most attenuation) goes from 92º shift @ 80Hz down towards 0º @ ~2KHz. With the attenuator at minimum attenuation, 80Hz gives 115º of shift ! The magnitude is equally hairy, theres a hefty drop from from 300Hz down to 80Hz of between 5 and 10db depending on settings. I threw together a basic circuit using LM386 and an op-amp that has an almost flat amplitude response and a much better phase response (32º @ 80Hz 10º @ 300Hz 2.5º @ 1KHz)... I'm not sure If this will be 'better' because of other issues, but its certainly a lot more linear. I've not tested other than simulating it so I'll not post it unless anyone really wants to try an untested circuit out. Should be a 'better' F/R (assuming it works). Plus if you use a dual opamp chip, theres a spare op-amp that can be used to stabilize the power, or provide harmonic modes, or to buffer the guitar through signal. cheers Col Edited February 27, 2008 by col Link to comment Share on other sites More sharing options...
Recommended Posts