psw Posted October 11, 2006 Author Report Share Posted October 11, 2006 I think curtis is right about the limiting function, but that's ok cause I think that is what we want. I am not sure if it will cause problems as my idea of a switch to cut gain at a particular threshold... In the end it is a little semantic...limiting is kind of the ultimate compression...kind of...I wish I had my compressor/limiter handy to play with it some more...both functions were independently controlable...oh well...another day, it wouldn't have provided "the circuit" but further proof of concept... Input from guitar -> buffer (buffered output here) -> preamp -> AGC etc... yes I do think this is preferable...it was the way I was thinking when I did devised an IC preamp circuit recently... I did make such circuits in the past but with little success...circuit design is not my forte obviously... Whether it actually makes much of a difference in our application though..? I think in our application anything that could prevent high frequency oscillation should be included. That is why I would suggest for instance, even if no extra gain is required from the 386, I would still put a resistor and 10uf cap between pins 1&8... It could be that an accumulation of such things and a bit of filtering could significantly improve things for you col. I repeat my support for what your circuit is trying to achieve, what ever the terminology and can only encourge you and curtis to keep thinking about it, or even consider other means of achieving it. I would also encourage trying to get as best a result without the AGC before taking this step, as long as the systems are still modular and it is practical to do this... must run also...best of luck... pete Link to comment Share on other sites More sharing options...
zfrittz6 Posted October 11, 2006 Report Share Posted October 11, 2006 Greetings. I am an admirer of this thread although I do not speak English I translate with google, so pardon by the phrases that can not be done well. I take to enough time following this thread and have made enough verifications. 1 - The conductors who I have done if they enrrollan themselves anyway give origin to a cancellation of the original sound and cause the overtones, so following an order in the winding purity in the sound is obtained but, and better sustain single is necessary to pay attention to as they estan winded the commercial coils and comparing them with ours. 2 - Good results than I have obtained are using amplifier of 2W commercial without preamplifier, problem whenever I have used preamplifying has be distortion which does to decay sustain, so I think that whichever but stages are worse, as a result of the noise that is generated. This I think yet that what better works is the simplicity and not to be complicated with preamplifying AGC nor that alter the purity of the vibration of the cords, at least in my case, that I repeat as better it works to me it is just by the stage of power without previous and the good disposition of the winding. Greetings from Spain Link to comment Share on other sites More sharing options...
zfrittz6 Posted October 11, 2006 Report Share Posted October 11, 2006 (edited) my conductor. 5,5 cm. x 1 cm. x 1 cm. constructed with thread of 0.24, internal magnet and tin cover of pepsi cola Edited October 11, 2006 by zfrittz6 Link to comment Share on other sites More sharing options...
psw Posted October 11, 2006 Author Report Share Posted October 11, 2006 Welcome zfrittz6...hola! Thanks for joining in, my spanish is no good and I hope my Australian can be understood. Well done, that looks great!!! It works ok then? How deep is your coil and is the magnet on the bottom? Mine is 3mm deep, quite thin... the blue part is the driver. You are right that the coil needs to be well made. I tend to agree also that less preamplification and more "headroom" (power) may give better results. A buffer would still be required to stop loading of the pickups and so that the amplifier runs efficiently. That said, my guitar's circuit uses a lot of preamplification and maximum gain from the amplifier...not clean...but works well. I tend to agree...AGC could make it more refined but I like the simple approach and I feel that extra circuitry burdens down the raw intention of the DIY Sustainer. It should work ok without it...the AGC should improve a good thing, it is not the answer to things like cross talk between the driver and the pickup. For further improvements on a well made driver, I think that the dual coil idea is the next step. It may be the "rail" design, a bi-lateral design or after much thought, I think the stacked design could work well. A major problem is the construction technique. I have failed to find any way of making suitable bobbins to wind around. This needs more thought and input from others as to how to best do this. This was always the thing that stopped me making my own pickup designs. So...I do think that the best solution will in the end be a simple but not perhaps obvious one.... pete Link to comment Share on other sites More sharing options...
bancika Posted October 11, 2006 Report Share Posted October 11, 2006 Hello, I joined "Tutorial" thread and was recommended to joint this monster thread I've tried to read last 10 or so pages, it's so hard to find stuff here Anyway, I've got a few questions: which is the last "official" circuit used to power driver. Is it still Fetzer/Ruby? I'm reading (mostly good stuff) about AGC but can't find what is it exactly? If I understood correctly, iron (Fe) does shield from EMI, so does shielding driver pickup help? I'll try to make one inside single coil cover, so I guess there will be space to insert iron cover around that won't be visible. If that's the case should I connect shield it to sustainter ground or guitar ground? What's the deal with split design. Is it just two separate coils? If yes, how should I drive them, using stereo amp or wire them in series/parallel and use them with mono amp? Thanks guys! Link to comment Share on other sites More sharing options...
Primal Posted October 11, 2006 Report Share Posted October 11, 2006 The Fetzer/Ruby is sort of the "standard" circuit for this project currently. Col's circuit is still under heavy development, which is one reason I'm putting off building it. I myself have made a successful Fetzer/Ruby amp. Regarding the shielding, we don't have a set "formula" for how to shield EMI. Feel free to experiment with it, though! The dual coil design is two coils wound to 4 Ohms (as opposed to one coil at 8 Ohm) connected in series so that you are in effect driving an 8 Ohm load. Using a stereo amp is certainly a possibility, however that would just eat batteries faster. For now, it would probably be good to experiment with a mono amp first. Link to comment Share on other sites More sharing options...
col Posted October 11, 2006 Report Share Posted October 11, 2006 Not quite. Limiting and compression both use the same "threshold" system. The only difference is that once the input exceeds the threshold in a compressor, the output continues increasing but at a slower rate. You can have a compressor set up with a 2:1 ratio, which means for every 2dB that the input exceeds the threshold, the output only increases 1 dB. Limiting is set such that any increase in input level over the threshold results in no increase in output, which in compression ratio terms is infinity:1. Not quite (hah) from wikipedia (I know I know.. not always the most accurate source)... (my underlining not theirs)... "A limiter is a compressor with a higher ratio, and generally a faster attack time. There is no absolute consensus on what ratio constitutes limiting as compared with compression, but most engineers would consider anything with a ratio greater than 10:1 as limiting. Compression and limiting are no different in process, just in degree and in the perceived effect. Engineers sometimes refer to soft and hard limiting which are differences of degree. The "harder" a limiter, the lower its threshold and the higher its ratio." You can add gain to the input of the compressor/limiter so that the quieter audio is louder and the louder audio is compressed - all you're doing is raising the average level of the audio by reducing the "distance" between the loud and quiet bits. yep all a compressor/limiter is is a gain stage and a feedback controlled gain reduction... ...its the feedback that controls the ratio.... OK, so lets think about my ACG circuit again. Lets assume that the first stage is white a high ratio - not quite a brick wall limiter (it's definately not), but a high compression ratio all the same. so below the threshold, theres lots of gain, then as you get close to and go past the threshold the gain drops quickly and smoothly..... So the function of the second stage in my circuit should still be working as I initially described. If the first stage had a low level input and didn't limit the gain much, the second stage won't limit the gain much either - so there will be nearly twice as much gain as would have been necessary to bring a quit signal up to the threshold.... Conversly, with a loud input into the first stage, there would be enough 'linearising feedback' to reduce the gain enough to bring the output down to the threshold.... the second stage does the same again - nearly twice as much gain reduction than would have been required to bring the output down to 'threshold'. So inputs louder than 'threshold' come out quieter than 'threshold' and those quieter come out louder... So we still have Dynamic Range Invertion irrespective of agruements about the technical details and differences between compressors and limiters... The impression I'm getting from the app note is that the threshold is defined by the 100K variable resistor (labelled "output amplitude"). It sets the absolute "ceiling" of the audio, above which nothing shall pass. I haven't built and tested this yet so I don't know exactly how it would behave in real life. Yes that sounds right - I remember that after some experiments, I found that For my purposes, it worked best with that set to minimum, so I just fixed it there and removed the pot. Since then, I've changed things around a bit, so it might be worth playing with that some more.... Anyway, if it works, it works Well, it kinda works It has the Dynamic range invertion thing going - this really does work. The problem is all the noise, and I don't think its all down to crosstalk... Theres a good chance that this circuit is causing problems because of bugs due to my limited knowledge. I'm learning lots through doing this - so its good, but still frustrating. My understanding of current is improving. It seems that one reason that a single passive divider won't cut it is because of the current in the LM13700s vcc/2 line. I was tweaking the resistor valuse in an trial and error fashion until I got the AGC response I was after, however, I wonder if there are better configurations that offer similar AGC performance but with better stability, lower current and less noise..... Edit: looking at your schematic, I wonder if you'd get better performance by changing the order of the buffer and preamp to: Input from guitar -> buffer (buffered output here) -> preamp -> AGC etc... ...instead of the buffer and preamp in parallel, the way it's currently drawn? And would the shared earth work properly if it was? Probably - I'm still trying to remove the need for the preamp gain stage - so there are just two unity gain buffers. I have an as yet untested variation that allows this - however I want to see if I can deal with the current issue, and have another look at that 100k 'output amplitude' pot befire I comit anything to solder Other stuff to try - I've read that using a large and small cap in parallel to filter noise from the power supply can help, maybe accross the LM386 power terminals... Also more filter caps - so each amp has one very close to its power pins... Absolutely! From the National Semiconductor Audio Handbook 1977: "...Shown or not, bypass capacitors are always required. Ceramic disc capacitors (0.1uF) or solid tantalum (1uF) with short leads, and located close (within one inch) to the integrated circuit are usually necessary to prevent interstage coupling through the power supply internal impedance. Inadequate bypassing will manifest itself by a low frequency oscillation called "motorboating" or by high frequency instabilities. Occasionally multiple bypassing is required where a 10uF (or larger) capacitor is used to absorb low frequency variations and a smaller 0.1uF disc is paralleled across it to prevent any high frequency feedback through the power supply lines..." Whether it actually makes much of a difference in our application though..? I think it might for my circuit ! I was just using cap values that seemed reasonable from what I've seen in other fx circuits. It seems though that most of those values are aimed at reducing lower frequency problems - powersupply hum, motorboating etc. The problems I'm having after my install _seem_ more like high frequency parasitics to me, and I don't have low value bypass caps !!! I've got stuff like 100u 22u 47u. probably should be more like 1u and 0.1u ? I've tried the fancy inter-8 weave style cable - it looks great and is fun to make (my wife said it could be used for jewelery), but it didn't make any noticable difference. Also although my driver casing seems to very effectively control the field of the magnet, removing it made little difference either way. That's why I'm focusing more on the circuit as a possible culprit for the problems I've been having. I would scrap the idea completely if it didn't work so well (apart from the noise) it really does make a big difference. Col Link to comment Share on other sites More sharing options...
psw Posted October 11, 2006 Author Report Share Posted October 11, 2006 Welcome again bancika Bancika posted on the sustainer tutorial thread and is also the creator of the DIY Layout Creator that I was raving about a few pages back!! which is the last "official" circuit used to power driver. Is it still Fetzer/Ruby? Yes it is. At the moment I would recomend it be made in two parts...the fetzer and the LM386 stage. Later, if something better comes along, you could replace the fetzer or amp stage, or insert an AGC circuit between. It may also be easier to build this way, especially since you have a layout for the fetzer already on your program. I'm reading (mostly good stuff) about AGC but can't find what is it exactly? AGC is "automatic gain control". Really a kind of limiter or extreme compression. The idea is that once the string is vibrating enough it does not need to be driven any harder. My guitar will continue to drive the strings until they physically can't viabrate any stronger or they crash into the frets!!! Member col has devised a circuit that cuts back the sustain once the string is vibrating enough. This may save power, but it mainly is aimed at evening out response and giving the sustain more refinement. I think col or curtis could explain the details better. There may be other ways of doing it, col has built and tested it, but it needs a little more work perhaps. AGC is featured in the commercial units by Sustainiac and Fernandes. Also, these feature phase correction circuitry. One difficulty is that there is a lag between the response of the driver coil and the speed at which the string vibrates. The result is a phase difference that can result in sweet and dead spots as well as a difficulty in driving the high strings. I have advocated driver designs that are fast enough to avoid such complicated circuitry although some simple AGC does have merit. The driver is really the heart of the device. You need good windings that are immune to vibration. Large amounts of glue is winded into the coil to achieve this. The other feature of my designs are very thin coils (mine is 3mm deep). The intention is to limit EMI to a compact area around the driver and to increase speed to overcome phase lag. If I understood correctly, iron (Fe) does shield from EMI, so does shielding driver pickup help? I'll try to make one inside single coil cover, so I guess there will be space to insert iron cover around that won't be visible. If that's the case should I connect shield it to sustainter ground or guitar ground? Yes...we sometimes have modeled such shields with a program called FEMM that simulates magnetc fields (in a very crude 2d way). This can give a feel for the shape of the field and the effects of things like this. You could try it down the sides of the driver to keep the field contained around the driver. Sucha a shield may have an adverse effect on a pickups sound if you are making a pickup/driver. I would not connect the shield to anything as it is likely that noise will enter the system... What's the deal with split design. Is it just two separate coils? If yes, how should I drive them, using stereo amp or wire them in series/parallel and use them with mono amp? At the moment we are looking into the next step in driver design. My thin coil desin is a simple 3mm deep single coil with a thin 3mm steel blade. A rail design (a small humbucking driver) is being tested to try and reduce EMI. It works just like a HB pickup, two opposing coils and magnetic fields. There are a number of schemes for dual coil designs that have come forward and a few variations I have suggested... > the rail side by side idea > a "bi-lateral" design with a coil under the high strings and another under the low (used by sustainiac) > two coils on their side with three blades (once used by fernandes) > a stacked coil, two single coils on top of each other I drew up a few versions. One I called a split blade...the intention was to combine the elements of the rail and bi-lateral designs. I do not know how well this would work or if a bi-lateral version would not be better. One intention is that one coil would drive the high strings and the other the low and that they could be driven by a stereo amp with different frequency responses for each set of strings. It could just as easily be driven by a mono amp in the same manner as the single or other dual coil designs. If you are building on top of a single coil pickup, my simple single coil design is proven and a good bet. A pictorial of how it was made can be found here... pictorial If you wanted to make a dedicated driver and wanted to get adventurous, a stacked driver may be the go. You may find magnetic shielding helps, of makes little difference. Otherwise, the main one being tested is the rail ideas. Hope that helps and wets your appetite...perhaps others could comment... pete Link to comment Share on other sites More sharing options...
psw Posted October 11, 2006 Author Report Share Posted October 11, 2006 I would scrap the idea completely if it didn't work so well (apart from the noise) it really does make a big difference. oh no.... the intention is right on, it may be the execution... it could well be circuitry noise at the heart of your noise problems. If so, you have made great strides in the driver design (I am a little dubious of magnetic shields after my own endeavours) and in the approach of the circuitry in general. I can't help thinking something couldn't be done in a simpler way. My preamp has a natural compression due to clipping form the high gain...every thing is loud!!! I think the problem with mine is it doesn't know when to quit...it needs something to say, enough already...that is AGC for me! The jury is still out about the whole clean driving thing, at least for me. I am sure someone made one of these with a big muff as a preamp (now there's clipped compression) and there was quite a bit of debate earlier about whether such a signal wouldn't be preferable. Of course any such clipping that may get into the pickup will sound particularly bad...but then we are seeking to eliminate that anyway...for that, the driver is the key... pete Link to comment Share on other sites More sharing options...
col Posted October 11, 2006 Report Share Posted October 11, 2006 (edited) oops - looks like I pretty much duplicated petes reply 2 posts up ... which is the last "official" circuit used to power driver. Is it still Fetzer/Ruby? There is no official circuit. The Fetzer/Ruby is surely not optimal - even as a simple buffer/power amp circuit for this application. My AGC circuit is not near comletion yet either - the published schematic is not as good as the current ones, and they're not nearly good enough yet Having said that, the Fetzer ruby is simple, easy to make and cheap, so use that until somthing better comes along. Use sockets for the transitor and LM386, so you can transfer them if you build a 'better' circuit in future. I'm reading (mostly good stuff) about AGC but can't find what is it exactly? AGC stands for Automatic Gain Control - another name for it is automatic level control. A compressor is a type of AGC. The idea of using it for a sustainer is that when the string is vibrating weakly and producing a low level signal, you need lots of amplification(gain) to make it vibrate more to give a good strong sustain effect. On the other hand if a string is vibrating strongly and producing a loud signal, you don't need much amplification at all to keep it going (and if a string is going so hard that it's bouncing off the frets, you don't want to give it any gain at all). This has two advantages for us: #1 It makes notes on any fret and on any string sustain at roughly the same level (instead of no sustain at all on high E string low fret, but way too much on g string high frets) #2 It uses much less power so batteries could last up to 5 or 6 times longer. This is because you only use power when its needed, so less is wasted. If I understood correctly, iron (Fe) does shield from EMI, so does shielding driver pickup help? I'll try to make one inside single coil cover, so I guess there will be space to insert iron cover around that won't be visible. If that's the case should I connect shield it to sustainter ground or guitar ground? iron can be used as a shield - it works by redirecting the magnetic flux. To what extent it helps in this application is not really understood yet. I have tried shielding all but the top of my driver, and it made little difference. Also be careful of the design of the shield, if you don't leave enough of a gap between shield and magnets, it will dramatically reduce the power of the field at the strings (probably a bad thing). What's the deal with split design. Is it just two separate coils? If yes, how should I drive them, using stereo amp or wire them in series/parallel and use them with mono amp? The split design helps to keep the magnetic field of the driver under control, reducing crosstalk between the driver and pickup. Wire it like a humbucher pickup, making sure that the magnet for the coil nearest the pickup has the same polarity as the pickup magnet nearest the driver... Good luck, Col Edited October 12, 2006 by col Link to comment Share on other sites More sharing options...
spazzyone Posted October 11, 2006 Report Share Posted October 11, 2006 (edited) Sorted out my recording problem (spyware chewing up memory) new clips are on the sound thread in straming audio no more downloads!!!!!! they are the second link (the soundclick one) here http://projectguitar.ibforums.com/index.ph...st&p=292613 im kinda laughing right now at all the technological mumbo jumbo as im getting awsome results with maybe $25 worth of junk im not trying to be rude at all. its just that im not an electronics guru and other than puting the rail pickup in a differant guitar i have not changed anything or experimented listen for yourselves....and i can't wait for Petes next experiment as im sure he will finally put the nail in the coffin here are two pics of current setup pic 1 guitar (note the "speaker wire" for the cable connecting driver to amp) real high tech ha.ha http://i32.photobucket.com/albums/d38/femf.../Picture008.jpg pic 2 the Rp6 with P.A/driver amp in backround (notice the mess of wires) adds no Emi or extra noise to my signal any noise is from the distortion/effects to the computer (i dont even get the normal computer monitor noise) http://i32.photobucket.com/albums/d38/femf.../Picture009.jpg Edited October 11, 2006 by spazzyone Link to comment Share on other sites More sharing options...
col Posted October 11, 2006 Report Share Posted October 11, 2006 im kinda laughing right now at all the technological mumbo jumbo as im getting awsome results with maybe $25 worth of junk im not trying to be rude at all. its just that im not an electronics guru and other than puting the rail pickup in a differant guitar i have not changed anything or experimented listen for yourselves....and i can't wait for Petes next experiment as im sure he will finally put the nail in the coffin Its great that you are happy with your setup The reason I am playing around with electronics mumbo jumbo (apart from that its fun) is that I want the whole thing to be cheap, easy to make and work from a battery - so the whole lot can be in my guitar. (I'd like to try this in an acoustic - with no external amp at all just an acoustic guitar that sustains forever ) It's all very well saying that you did the whole thing for $25, but does that include the Amp? Is that amp something thats easily available for everyone ? Maybe for the project to go the 'high power external PA' route, we need to get a PA style circuit that everyone can build.... which could be even more tricky - it certainly would be much more dangerous. Another potential issue is the longevity of the system - It's still not certain how long an un-modified rail pickup will last having so much power pumped through it for sustained (no pun intended) periods. (of course, there are going to be issues no matter which route we choose to take - maybe we will end up with two equally good different systems that folks can choose from depending on their requirements) I hope Pete also gets good results from your ideas, and maybe we can get an idea of the voltages and currents involved and think about the long term practicalities of the setup... cheers Col Link to comment Share on other sites More sharing options...
spazzyone Posted October 11, 2006 Report Share Posted October 11, 2006 (edited) Hey Col On the acoustic i'd agree onboard electronis apears to be the only way and i can understand the fun factor as for the $25 that includes the pickup and the P.A amp (a cheap 20 watt radioshack) found at a swap meet the rest of the setup is standard stuff every electric guitar player would have the pickup was $12.99 buy it now on ebay and for $38 bucks i can equip three guitars and so for like $50 bucks ill have three guitars loaded ready to go with no Emi/Noise/batteries or other problems that seem to keep popping up on every body on this thread and i only turn the amp up a quarter of the way (i could probably use one of those (mini amps) like 9 volt fender/marshall things) and it would probably work as the headphones on my MP3 player drown out the P.A amp turned that low (yes thats a joke) but its close (if i turn the volume past half the strings vibrate out of control rendering it useless for playing) as far as the pickup lasting. ive been using it since june (at first a i ran it on the 70 volt output of the amp but after Petes warning i stopped) but now i use the 16ohm output and it's still turned on from recording yesterday and the coils aren't even warm im not at all saying my way is best as i realy have no clue. but i does work good im just suggesting trying something like it. because if you had my setup im sure you would have it blowing away the fernandes/sustainiac systems because of your knowledge how to modify it better i know how to trouble shoot to a certain degree and can work off a schematic but could never design the stuff you guys are talking about how can i get the voltage/current readings from the amp? i have a fluke meter but not sure how to use it in this manner. but i could tell you guys how much power its taking to power the rail. which maybe of interest to help in everyones designs the main reason i like this setup is that once i figure out the phase reversal issue (maybe someone can help me with this?) i can make a floor controller that would have an sustainer on/of switch a phase reverse switch and two expression pedal outputs one for sensitivity the other as a blend pedal so i can bring it in or out at will with the original signal without removing either hand from playing and i wasn't trying to be rude in my last post when i said i was laughing its just when i hear about AGC's and all the likewise circuts it makes me wonder if i already have stuff like that in my system without even knowing it Edited October 12, 2006 by spazzyone Link to comment Share on other sites More sharing options...
col Posted October 11, 2006 Report Share Posted October 11, 2006 Hey Col On the acoustic i'd agree onboard electronis apears to be the only way and i can understand the fun factor as for the $25 that includes the pickup and the P.A amp (a cheap 20 watt radioshack) found at a swap meet Thats the bit I'm questioning pricewise What I'm saying is how much does the whole thing cost NEW - pickup = $13 which is cool, but how much for a usable readily available 20 watt amp ? ...ready to go with no Emi/Noise/batteries or other problems that seem to keep popping up on every body on this thread It makes sense that you have little or no trouble with emi and noise. Using a pickup means that you won't have problems with the driver and pickup acting like a transformer. Using an off-board amp means no worries about interference between the amp and pickup/driver due to close proximity. (Also, the Amp has been designed by professional electronics engineers rather than ignorant amatures) Obviously if you don't use batteries - thats not a problem Ive been using it since june (at first a i ran it on the 70 volt output of the amp but after Petes warning i stopped) but now i use the 16ohm output... This is interesting - it sounds like it will be very inefficient, but that doesn't matter because it's not battery powered - and my setup has shown that you can get the strings going with very little power, so its not surprising that even with some major inefficiency due to imedence mismatch, it still doesn't need that much juice. how can i get the voltage/current readings from the amp? i have a fluke sm 77 but not sure how to use it in this manner. but i could tell you guys how much power its taking to power the rail. which maybe of interest to help in everyones designs for voltage, just set the meter to ac voltage, and put one probe on each of the driver leads. for current, set to ac current (you'll have to put the lead plugs in the correct sockets and make sure to try on the 10A setting first(read the manual)), then disconnect one of the driver leads, and patch the meter inbetween. the main reason i like this setup is that once i figure out the phase reversal issue (maybe someone can help me with this?) it may not be simple to fix this - it probably a combination of the phase response of your PA amp and the high impedence driver.... so it could be a 'feature' of your setup. cheers Col Link to comment Share on other sites More sharing options...
spazzyone Posted October 11, 2006 Report Share Posted October 11, 2006 on the voltage i get a reading of 0.42v current reads 0.11 Link to comment Share on other sites More sharing options...
col Posted October 11, 2006 Report Share Posted October 11, 2006 on the voltage i get a reading of 0.42v current reads 0.11 current sounds right, voltage isn't what I expected, maybe I told you to measure the wrong thing... maybe curtis can help us here ? Col Link to comment Share on other sites More sharing options...
curtisa Posted October 11, 2006 Report Share Posted October 11, 2006 Not quite (hah) from wikipedia (I know I know.. not always the most accurate source)... (my underlining not theirs)... "A limiter is a compressor with a higher ratio, and generally a faster attack time. There is no absolute consensus on what ratio constitutes limiting as compared with compression, but most engineers would consider anything with a ratio greater than 10:1 as limiting. Compression and limiting are no different in process, just in degree and in the perceived effect. Engineers sometimes refer to soft and hard limiting which are differences of degree. The "harder" a limiter, the lower its threshold and the higher its ratio." Uhh...Isn't this what I said anyway? Limiting = compression except for a much higher ratio. Whatever! Compression. Limiting. Doesn't matter - we're just attempting to average out the driver signal I'm learning lots through doing this - so its good, but still frustrating. My understanding of current is improving. It seems that one reason that a single passive divider won't cut it is because of the current in the LM13700s vcc/2 line. I was tweaking the resistor valuse in an trial and error fashion until I got the AGC response I was after, however, I wonder if there are better configurations that offer similar AGC performance but with better stability, lower current and less noise..... Well, the LM13700 isn't exactly reknowned for it's audio performance. The companies that produce commercial compressors and limiters use much more esoteric circuits based around higher cost dedicated VCA chips. I did actually try breadboarding up the circuit in the LM13700 app note last night, but it refused to work - all I was getting was really nasty distortion as soon as the input exceeded a certain threshold which seemed to have nothing to do with the "output amplitude" pot. I don't have a second LM13700 to swap out to see if the first one was faulty though. I want to try a variation on the compressor idea using a completely different IC, a SSM2018, which is a professional dedicated VCA chip. I'm expecting much more predictable results using it, but the unfortunate thing about this IC is that it's particularly hard to get and quite expensive, at least here in Australia. Probably - I'm still trying to remove the need for the preamp gain stage - so there are just two unity gain buffers. I have an as yet untested variation that allows this - however I want to see if I can deal with the current issue, and have another look at that 100k 'output amplitude' pot befire I comit anything to solder I think you will need some form of preamp gain because the AGC will expect to see higher input levels than what a guitar can typically deliver. Shouldn't need too much though, say 10-12dB extra. I'm finding the really frustrating thing about my setup is that I'm 99.99999% sure that adding compression to the driver signal should even out a lot of inconsistencies, but each time I go to test the theory I always get better results using the straight LM386 circuit. D'oh! Pete: I just noticed your request for audio samples in one of your earlier posts further up - I'll try to record some samples of my setup this weekend coming so that you can compare my driver performance to yours. Cheers, Curtis. on the voltage i get a reading of 0.42v current reads 0.11 current sounds right, voltage isn't what I expected, maybe I told you to measure the wrong thing... maybe curtis can help us here ? Col Are you changing the meter probe positions when you change from AC current to AC voltage? Current measurements need to be taken with the meter in series with the circuit you're measuring. Voltage measurements need to be done with the meter across the circuit. Cheers, Curtis. Link to comment Share on other sites More sharing options...
col Posted October 11, 2006 Report Share Posted October 11, 2006 (edited) I want to try a variation on the compressor idea using a completely different IC, a SSM2018, which is a professional dedicated VCA chip. I'm expecting much more predictable results using it, but the unfortunate thing about this IC is that it's particularly hard to get and quite expensive, at least here in Australia. Is the SSM2018 available in a DIP package? Probably - I'm still trying to remove the need for the preamp gain stage - so there are just two unity gain buffers. I have an as yet untested variation that allows this - however I want to see if I can deal with the current issue, and have another look at that 100k 'output amplitude' pot befire I comit anything to solder I think you will need some form of preamp gain because the AGC will expect to see higher input levels than what a guitar can typically deliver. Shouldn't need too much though, say 10-12dB extra. With the right setup the LM13700 can provide plenty gain.... no guarantees, but I think it can be made to work. Problem is that huge input resistor - I'm guessing that is there to stop the divider pot on the input from pulling the dc levels of the previous stage out of whack. I guess its about what the stage is... it's output impedence ? I have a question about bypass caps - one good source says to bypass both the negative and positive supply to ground. Should I bypass +v and -ve supply pins to vcc/2 ? (maybe a silly question) or just the +ve to ground and vcc/2 to ground... if the second option, where is best to put the cap? cheers Col Edited October 11, 2006 by col Link to comment Share on other sites More sharing options...
spazzyone Posted October 11, 2006 Report Share Posted October 11, 2006 (edited) Not quite (hah) from wikipedia (I know I know.. not always the most accurate source)... (my underlining not theirs)... "A limiter is a compressor with a higher ratio, and generally a faster attack time. There is no absolute consensus on what ratio constitutes limiting as compared with compression, but most engineers would consider anything with a ratio greater than 10:1 as limiting. Compression and limiting are no different in process, just in degree and in the perceived effect. Engineers sometimes refer to soft and hard limiting which are differences of degree. The "harder" a limiter, the lower its threshold and the higher its ratio." Uhh...Isn't this what I said anyway? Limiting = compression except for a much higher ratio. Whatever! Compression. Limiting. Doesn't matter - we're just attempting to average out the driver signal I'm learning lots through doing this - so its good, but still frustrating. My understanding of current is improving. It seems that one reason that a single passive divider won't cut it is because of the current in the LM13700s vcc/2 line. I was tweaking the resistor valuse in an trial and error fashion until I got the AGC response I was after, however, I wonder if there are better configurations that offer similar AGC performance but with better stability, lower current and less noise..... Well, the LM13700 isn't exactly reknowned for it's audio performance. The companies that produce commercial compressors and limiters use much more esoteric circuits based around higher cost dedicated VCA chips. I did actually try breadboarding up the circuit in the LM13700 app note last night, but it refused to work - all I was getting was really nasty distortion as soon as the input exceeded a certain threshold which seemed to have nothing to do with the "output amplitude" pot. I don't have a second LM13700 to swap out to see if the first one was faulty though. I want to try a variation on the compressor idea using a completely different IC, a SSM2018, which is a professional dedicated VCA chip. I'm expecting much more predictable results using it, but the unfortunate thing about this IC is that it's particularly hard to get and quite expensive, at least here in Australia. Probably - I'm still trying to remove the need for the preamp gain stage - so there are just two unity gain buffers. I have an as yet untested variation that allows this - however I want to see if I can deal with the current issue, and have another look at that 100k 'output amplitude' pot befire I comit anything to solder I think you will need some form of preamp gain because the AGC will expect to see higher input levels than what a guitar can typically deliver. Shouldn't need too much though, say 10-12dB extra. I'm finding the really frustrating thing about my setup is that I'm 99.99999% sure that adding compression to the driver signal should even out a lot of inconsistencies, but each time I go to test the theory I always get better results using the straight LM386 circuit. D'oh! Pete: I just noticed your request for audio samples in one of your earlier posts further up - I'll try to record some samples of my setup this weekend coming so that you can compare my driver performance to yours. Cheers, Curtis. on the voltage i get a reading of 0.42v current reads 0.11 current sounds right, voltage isn't what I expected, maybe I told you to measure the wrong thing... maybe curtis can help us here ? Col Are you changing the meter probe positions when you change from AC current to AC voltage? Current measurements need to be taken with the meter in series with the circuit you're measuring. Voltage measurements need to be done with the meter across the circuit. Cheers, Curtis. yes ac voltage is the first setting on my meter and i stuck the pos probe in the 16ohm jack and the neg probe in the common jack for that reading and for current i removed the driver lead going to the 16 ohm output and placed the neg probe in the jack. with the neg driver going to the common jack then the pos probe to the pos driver lead. and on my meter the neg is connected to the 10 A connection and the meter is set to amps and its an auto ranging meter so im reading what it shows does this sound correct? Edited October 11, 2006 by spazzyone Link to comment Share on other sites More sharing options...
psw Posted October 11, 2006 Author Report Share Posted October 11, 2006 (edited) I hope Pete also gets good results from your ideas, and maybe we can get an idea of the voltages and currents involved and think about the long term practicalities of the setup... Remember what I said about this thread being about Sustainer Ideas (with a bias towards DIY approaches and furthering the technology)? Anything goes, so we must respect anything that is suggested and tried...keep an open mind! That said...I did try, as have many others to get a standard pickup to work as a driver without success. Obviously shawn has achieved something by the evidence of the latest sound clips. There is no denying something is going on here, but I too am wary of the practicalities. From a technical point of view also, there is a big difference between a load of 16 ohm and 14,000 ohm as we have here. At the very least it is inefficient. Micheal Brook addressed this problem with some kind of transformer, and this approach has been suggested by someone else here also. I had thought the main problem would be speed of response of such a large coil and the fragility of the windings. When I originally tried experiments with a crude coil and a hifi amp I got tremendous heat...enough to burn. Now this was with thicker wire (thicker than I am using now). Without giving too much away, my hex design elements were very fragile and contained delicate components and also generated a lot of heat (a lot of power through a thin wire will do that) and needed the protection of quite a bit of heat sinking in order for it not to self destruct. If you were experienceing such heat, I think you would know (smell!) it. I do still however favour a dedicated purpose built low impedance driver for a number of reasons. Your experiences though may she some light into the way driver's perform and the development of this area anyway, so it is worthy of note, even if not pursueing this part. The next stage is as you say to make some kind of floor controler as you described... must run, but will post something on that and the phase reversal switch when able... pete ps...I would have expected something like 4.2 volts to be comming out of an amp at least... Edited October 11, 2006 by psw Link to comment Share on other sites More sharing options...
bancika Posted October 11, 2006 Report Share Posted October 11, 2006 Hi Guys, me again. I drew layout for Fetzer/Ruby on 13x7 perfboard. I don't have necessary components at the moment so I can't veryfy it now, but should be fine. It uses in-line trimmers, but can be easily adapted for other types Here's link to GIF file And .DIY file Cheers Link to comment Share on other sites More sharing options...
col Posted October 12, 2006 Report Share Posted October 12, 2006 (edited) DAAAAMMMMMMNNNNNNN what a bbbbbaaaaaa..... So, I'm preparing to hack some extra bypass caps into my circuit, and searching for the correct pin/track from the LM13700 when I discover one of the pins was never soldered !!!! Whats more not only is it pin8 which is the source of the all important AGC control current, it is also making a good enough mechanical contact so the circuit works, but is noisy. So after fixing that, Things are a WHOLE lot better. Still not perfect, but better than my breadboard setup. I still put in the extra bypass caps, but they didn't have any noticable effect. So, now that the fizz is no where near as bad, I will re-install the driver shield to see if that now makes an audible difference. After Curtis' comments regarding the virtual ground dividers etc. I've done some reading, and have some new ideas about how to possibly make the whole thing more stable... but that will involve a total rebuild, so I want to spend some more time on the design... and I need to go buy some parts... anyway I'm kinda happy, but also really annoyed Col Edited October 12, 2006 by col Link to comment Share on other sites More sharing options...
ebenezer shred Posted October 12, 2006 Report Share Posted October 12, 2006 col, you're my hero. The only thing i was worried about on this project was whether or not I could build this circuit, but now I can see it's not too difficult Link to comment Share on other sites More sharing options...
psw Posted October 12, 2006 Author Report Share Posted October 12, 2006 (edited) Good stuff, bancika I drew layout for Fetzer/Ruby on 13x7 perfboard. I don't have necessary components at the moment so I can't veryfy it now, but should be fine. It uses in-line trimmers, but can be easily adapted for other types People want to go over this and check it out??? The great thing about this is with bancika's program and file posted above, we can correct, modify or improve this circuit. Now that is simple and compact, cheap too! I don't think the F-R is the last word in circuitry, on mine C5 is a 100uF for better high string response but you get some harmonic effect on the lower strings (I like it!)...I'd also like to see a 10uF cap between pins 1&8, a diode for power protection and a resistor for an LED...that's me though, primal effectively made this and it worked fine. Given col runs the LM386 at minimum gain with a high powered humbucker, perhaps this is all that is required on some guitars... Speaking of which... So, I'm preparing to hack some extra bypass caps into my circuit, and searching for the correct pin/track from the LM13700 when I discover one of the pins was never soldered !!!! Whats more not only is it pin8 which is the source of the all important AGC control current, it is also making a good enough mechanical contact so the circuit works, but is noisy. funny that, my guitar has a fault, the cap between pins 1 & 8 on my guitar has a dry solder joint or something and I can detach the cap. Sometimes the guitar looses power and that is the cause...so it will work with minimum gain is one thing, and even if built with a soldering station, digital heated iron and a fair bit of practice...constant modes will take their tole on components and such (maybe that's my fizz too). Unfortunately, I have no access to such equipment just now, so I have to live with it as is and occasionally hit it! So after fixing that, Things are a WHOLE lot better. That is good news...and a bit weird because with any tested circuit with such faults the first thing anyone says is to check thiose solder joints...d'oh DAAAAMMMMMMNNNNNNN what a bbbbbaaaaaa..... nothing is lost in translation.... So good news...I really am pleased Now, I know this is probably not going to be taken too well, but what about a compression circuit that uses an op-amp with two diodes in the feedback loop...common in circuits like the tubescreamer? I know this will cause clipping, but it will effectively limit the signal to a given level. I went to the library today and looked up some simple AGC circuits like this. Shawn...the harmonic switch is simply a phase switch as found on guitars. It uses a DPDT switch (very common in those stomp box footswitches) and would be wired on the driver leads like so... You will find there are a lot of very simple IC based amps that could be built into some kind of pedal and a volume footpedal an excellent idea...how much power you need to get what you are achieving may still need some work, if you are to continue with this approach to the sustainer. The other issue that you will likely face is that signal wires in the guitar lead and the speaker leads to your driver wont like to be mixed at all...separte and separated leads are probably going to be a necessity... You are most likely going to need some kind of buffer or splitter to stop the guitar's pickups from being loaded down also...you could run it after effects that could serve that purpose though. It is interesting to consider if a circuit could be devised (perhaps an op-amp) that could drive a 14k load with sufficient gain from a battery. Perhaps such an amplifier would have such improvements in efficiency that battery power and onboard electronics is possible. Either way, your experiments certainly have opened peoples eyes to the possibility of the rail style of pickup for low impedance driver technology. This has been a very interesting and quick moving era of the sustainer thread that I have found enjoyable and quite unexpected. It is great to see that even though my ability to contribute actively in develoments (contribuing my 99% perspiration...and it's stinky hot today down here), developments are still taking place and new things still being tried... The thread is in good hands and still vital, simply amazing. Also staggering is the number of visits 64,623, thats a few thousnad over the last few weeks !!! If only it was pay per view or we had some google adds or something...hehehe... pete EDIT...changed to bancika's gif which sows trim pots, unlike the layout .diy file I uploaded (perhaps I have an earlier verison of the software or something...?) Edited October 12, 2006 by psw Link to comment Share on other sites More sharing options...
zfrittz6 Posted October 12, 2006 Report Share Posted October 12, 2006 PSW. the measures of the magnet that I use are of 5.5 cm. in length, 0.3 cm. wide and 0,5cm of stop, everything with enough plates removed from the softdrink cans to isolate EMI and works perfectly, also to say that it reaches the conclusion that at least clean circuit and but is better, because utilize in principle the fetzel-ruby and tapeworm too much noise and probe with my rp-6 of digitech in clean with lm386 and worked enough good, so buys an amplifier of 2w and single I put that to him and is when really I work of wonder, I have to directly say also that to the coil enrrolle to the magnet trying that the thread was crossed less possible not if I explain myself that is to say, if empizo by down I am enrrollando upwards without cruzes in the thread and later downwards up to 160 returns, 8 ohms altogether. In the end without previous it does not notice either that it lowers as soon as the signal towards the amplifier. thing also I have other two bibinas done of 4 ohms each one and the measures are 3mm. by 3mm. by 5.5 cm. which I have still not proven, the nucleus of these I have done it with worn out magnet and magnetized North it arrives and the south down but I have not been able to verify its operation with my guitar which is a ibanez gem-555 and for which me vendria very well. also to say that if makes lack design pcb of some circuit in smd or normal as well as some type of electronic switch here me teneis to your disposition. Greetings. Link to comment Share on other sites More sharing options...
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