utopian isotope

Anyone here that has tested/experienced NE571(SA571) as compressor/limiter? Off-topic this might be, but after reading about that AGC-stuff here, I searched my components, and found some NE571's. It is some kind of compressor/expander(compander) chip. Originally one of those was used in Craig Anderton's "Roctave Divider", that I built years ago. It seems to be quite rare chip, since I haven't found much information about how to use it as a compressor and/or limiter. -------------------------------- @psw: I'm just curious about that PLL. I assume you mean 4046 or similar? How did you use it, if I may ask? interesting subject it is (atleast for me), because I (ab)used that chip on some of my testings in the past.

"first though. I don't think you will find anything by searching as if it is in this thread, which it is, the search function will bring up the whole thread...not the relevant post...a big problem finding things now the thread is soooo looooong... hmm, I've found that by using the search topic box at the bottom of each page, I can very successfully search for individual posts within this single thread (thats what its for ;p) I can usually find any particular post or discussion I'm looking for from way back when within a few minutes... assuming of course that I can remember the topic under discussion e.g. go an put LM13700 into that search box (at the bottom left of this page), you should get about 3 pages of results - certainly a manageable quantity... then when you found the post in the results, click on the 'Post Preview' link under it to jump to the parth of the main thread it came from." cheers Col Thanks for the searching tips. ------------------------ psw wrote:"With the neck pickup wires open, there is at least twice the power and quite a different harmonic response compared to shorted together (still not connected to anything else). Quite bizarre. The driver setup does not like the harmonic mode, requiring the power to be decreased a lot and then only responds properly on the lower strings...hmmm" That reminds me of an electric motor; if you spin its axle when leads aren't shorted, it rotates more freely when compared to leads shorted-situation. When shorted, it resists spinning much more. Shorting coil(s) seems to "freeze" their magnetic field in some way. I assume that shorted pickup does something similar to the strings. ----------------------------- col wrote:"What about the stronger sustain and the warm singing full bodied tone that you get from a loud amp ? It doesn't have any lag - you get it from when you hit the string! and it is arguably even more important then classic 'feedback'! If this effect can be produced (at least in part) by a sustainer, then its unlikely to work if the sustainer doesn't kick in until natural feedback would start to occur (this is a limitation of my existing system, so I am talking from experience)" Yep, you are right. But to get more live sounding feedback, some overdriving is necessary at some stage? Of course it depends on what kind of sound you like. Some examples of my favourites are live sounds from Jimi, Jimmy Page, Pete Townsend, Santana and Tony Iommi. Quite raw stuff, but all of those use fuzz/distortion/overdrive, so that feedback is easier to produce. And also easier to imitate. Maybe some day I make some samples and post them here.

Some thoughts again.. @col: If I remember right, you are using sustainer, that has an AGC? If so, does it have a "pick filter" -properties in it? ------------- @col and psw: When you pick a string or hit chord, there is always signal peak, before string(s) settle and vibrate at their fundamental note. That peak goes to sustainer and is amplified(unnecessarily?) too, causing less efficiency. ---------------------- It came to my mind when testing things and listening some live recordings. Feedback really doesn't seem to start at the time you hit string(s), unless you have some uranium-core pickups and wall of amps that go to 11. ---------------- Anyway, I'm sorry if this subject is discussed earlier. Tried that topic search with word AGC, but it doesn't seem to allow that short acronym. --------------------------- @disndat: This thread just might be focusing more on DIY, rather than modifying readily available commercial products. Browse and read this thread, if you want to know more about the essence of sustainer. And maybe post some audio for us to listen as a reference.

Yep, I have tried piezo, but it doesn't have the same "body" as (in my case P-90). Instead I got some awful howling out of it, when testing. It doesn't create as much low frequency feedback(without preamp), as magnetic pickup does, that is needed for strings and guitar body to vibrate. Maybe enough for an acoustic, but not for solid body. ----------------- Flash from the past: some 15 years ago I struggled with feedback, after listening Jimi, "how can I get that sound". So I took speaker, mounted it in back of my guitar, and hooked it in stereo amp. "More low frequencies", I said. Finally I got some feedback, till that speaker started to smoke. End of the story. ----------------------- But all in all we are closer to those sounds than ever before, if commercial things aren't counted.

"I have a pretty good understanding of what happens with a bowed string - how it sounds, and a basic understanding of the physics (one of my other interests is digital signal processing, and I have read some papers on modeling a bowed string digitally. The math is heavy, but there are good explanations of what's happening when a string gets bowed.... and it has very little in common with soft or hard clipped fuzz...)". ----------------------------------------------------- Mathematics is something I don't understand, but hearing and seeing is what I understand better. And no, I'm not talking about modern fuzz or distortion. What I mean is "natural harmonic distortion", that has been over 200-300 years, maybe more, since stringed and bowed instruments were developed. If you bow an E and A strings simultaneously, you will get totally different sound, compared to plucking; almost like a choir of those two strings; no clean tone is available there. Simply too much overtones for that purpose. -------------------- No oscilloscopes are available for me, so I just listen sounds. --------------------------- Addition to that loop-thing: Aluminum isn't too good solution, because wires can't be soldered to it. Copper or brass suits better. I'm going to make new loop out of thin copper plate, to make it more reliable.

Did some mind(less)storming again after reading previous posts. Especially that "violinish" tone and sustain -thing. When I saw Led Zeppelin's "song remains the same" -live long time ago, I thought: "wow I want that bow!". And so I bought me one. Tried it with both electric and acoustic, and got quite cello-like sounds at lower strings. Higher strings gave more screeching. --------------------- What I'm after, is that when you listen to real cello sound, when bowed at lower strings, it doesn't sound nowhere as clean as guitar or bass (with clean tones). Reason why I stress those lower strings, is that it is more noticeable(at least for my ears), since cello is like slow-motion version of violin. ---------------- On guitar or bass, you pluck the strings, instead of rubbing them with a bow, letting them to vibrate freely, so that they produce sine wave without too much overtones, when compared to bowing. If we look free string vibration as a sine wave, bowing kind of "limits" strings natural movement, thus cutting its sine wave. As we know, cutting sine wave causes clipping ---> distortion ---->overtones. That's why I came to conclusion, that instead of hunting too clean sound and feedback, more overtones should be added. "Natural harmonic distortion" seems to be a major part of that desired tone. ---------------------------- As I've read these postings, distortion or fuzz/fizz seems to be the problem on the sustainer-circuit(s). Maybe it is just pure nature of tone and feedback, that tries to push out, in form of fuzz/fizz? ----------------------- If possible, get yourself a violin bow(some rosin also) and test things. Compare sounds between bowed and plucked note, so you'll see(hear) what I mean.

Thanks col, I'll try it. I listened your demos, and they give quite good picture of sustainers possibilities. ---------- Seems that some of that annoying fuzz-element came from lower strings rattling against frets. So I decreased lower frequencies on that eq. Clean tones sounds much better now, although there is still subtle amount of fuzz (clipping/distortion). Addition: I also replaced battery with mains adapter. It seems to give more headroom to sustainer, so that it doesn't clip so easily. Not too practical, but as I'm testing things, it doesn't bother. When enough testing is done with my present sustainer, I'm going to replace it with Ruby/Fetzer for better efficiency.

How do you post an audio clip here? Since Photobucket doesn't allow mp3 or any other audio-formats? Do I really have to have my own website, where I can upload the files, so that I can link them here ?

Sounds interesting - here is a crucial question for you: When you set your amp and guitar for a crystal clear clean tone, does the sustainer add some (subtle or otherwise) fuzz to the sound ? You see, the thing I and many others are concerned about is not squeal - that's easy enough to deal with - the really difficult thing to deal with is background fuzz. So do you get a nice clear clean sound with loads of feedback ? can you post an audio clip ? -------------- Yes, it adds fuzz, even at minimum gain, especially at lower strings. With clean tones, it is too disturbing. I guess that the fuzz or distortion (clipping) has something to do with sustainer circuits headroom. - - - - - - - - As psw wrote earlier: Besides the EMI problem that cause squeal if the device is too close to the pickup driving it, I think a lot of the distortion is more caused by driving the strings too hard...I have tested a diode pair to limit this with a bit of success. -------------- Key element seems to be to limit sustainers input to the level, where it can't clip at any case. Since lower strings contain more iron, they are more prone to vibrate and cause feedback. They produce more and more signal to the sustainer, finally so much that clipping occurs. -------------- Maybe I take my present (although overpowered) sustainer circuit, do some measurings and throw few diodes to its input. Since diodes limit only voltage, not current, they are better choice instead of resistors, that limits both current and voltage (correct me if I'm wrong). -------------- Audio clip? If (when) I get good clean tones with clean feedback. --------------------------- Did some brainstorming on diodes, and came to conclusion, that those diodes limiting capacity depends directly on voltage that is fed to them. What I mean is to have some sort of permanent "gate" or "window", that accepts only a certain amount of voltage(for example 0-20mV) from the driver, so that clipping doesn't occur. Those diodes seems to give "signal - minus diodes voltage-dropping" -effect, instead of permanent 0 - (whatever is your sustainers headroom) mV window.

Yes it would be an ideal solution, but since that loop is more capacitive/inductive element, additional resistance would add unnecessary stress to sustainer circuit.

One thing to watch out for is that steel has a fairly high magnetic permiability, so putting a lump of steel near your pickup could have some negative effect on the sound of the pickup ! I would stick to aluminium or copper for this reason. ------------------------------- My guess about the need for 'tuning' is that if the wire loop is creating more interference current than the driver it will cause squeal/noise and if the driver is creating more interference current it in turn will be the culprit, 'tuning' is basically the process of tweaking the level of interference that the loop is causing so that it matches the driver and they cancel With this in mind, it may be possible to setup the loop with a low resistance trimpot so that 'tuning' can be done with a screwdriver! Yes it would be an ideal solution, but since that loop is more capacitive/inductive element, additional resistance would add unnecessary stress to sustainer circuit. ------------------------------------------- btw, utop iso, are you using a basic mechanical switch to flip the driver connections as your harmonic switch? No switches used, just plain point-to point wiring, as I am experimenting things. --------------------------------------------------------------------------------------------------------- Depending on the pickups polarity, there is only one 'correct' polarity for the driver. In the past, some people have had more noise in normal mode and some in harmonic - me and another poster (can't remember who but he explained it better than I did?) came to the same conclusion as to why - something to do with shared earth and polarity of the coils, but anyway - my understanding is that either normal or harmonic mode will be noisy unless you use an op-amp inverter in the preamp for mode switching. No inverter is in use; just an eq, that acts as a buffer with some gain on certain frequencies.

Have you tried positioning it around the pickup ? If that works, it would be ideal in terms of minimizing space requirements and making it look better. What kind of adjustments do you make to 'tune' it in ? What happens when you switch the polarity of the loop, does is then fail to work ? Loop around pickup is what I also have in mind. Should it be wrapped around pickups cover or straight around to pickups coil... that is something I'm going to test. ----------------------------------------- Tuning the loop position? All you have to do is to use driver in harmonic mode(that's what I have used while experimenting loop, because it seems to be more willing to squeal), and increase sustainer gain enough that it starts to squeal. Then take loop and move it close to driver and pickup. Near the pickup, you should get some weird theremin sounds. That's where "tuning" starts. It might take some time to find that "sweet spot", but when you get to that point, squealing stops suddenly. To verify that, increase sustainer gain even further. No squeal should appear. ------------------------------------------- Because all guitar/pickup combinations are different, free experimenting is suggested. --------------------------------------------- Polarity seems to be one of the key elements. You can change loop polarity by switching its wires, or just flip the loop upside down. If polarity isn't right, it fails to work, and you don't get much audible results. So "tuning" is done by ear. --------------------------------------------- Note on loop construction: Wire loop isn't too stable, unless it is glued on something that preserves its shape. Nevertheless it is acceptable, but I still encourage you to make the loop out of an aluminum, brass, steel or copper plate; so that it keeps its shape and is more solid. Doesn't matter how thin plate is, as long as it doesn't vibrate along the (electro)magnetic flux. Solid loop should take care of that squeal-phenomenon.

I've been doing some experiments with that loop, and replaced wire with loop I made made of kitchen aluminum foil. It's too thin to handle, so I sandwitched it between two layer of adhesive film. Purpose for this is that I wanted as thin loop as possible. It does the trick same way as wire loop when positioned between driver an pickup. Strange thing is that it works also behind the pickup!! Since I have LP Junior-type bridge, under it is enough room to place loop there. The more I experiment with it, less I understand... Positioning the loop is quite critical anyway, so it takes some "tuning" to find that sweet spot, where squealing goes away. Wires that I used to connect aluminum foil loop to driver, were braided and not twisted. At least I didn't notice difference between straight and twisted wires.

@ psw: I meant that the loop "binds" or limits driver's magnetic flux, and prevents its affection to PU. Because that loop is between driver an PU, it allows the driver to concentrate magnetic force on strings, instead of PU. @col: You just might be on the right track about that loop thing.. somehow your text makes sense to me. In practice it is simple, but in theory it is far beyond my knowledge. Maybe the pickup "sees" drivers magnetic field as a parasitic element? And the loop works as a sink or drain that absorbs most of the parasitic forces? ---------------------------------------------------- Lot of discussion here about that switching thing.. got stuck when reading it..almost forgot that loop thing. Some day, when I get that strat together, I'll read whole story.

Dimensions of magnet: length: 60 mm, width: 14,3 mm, and thickness: 5,5 mm. Coil thickness: about 4 mm Coil is wrapped directly around the magnet. I rounded the magnet's corners, so that it was easier to wound. With that amp, I use single 9v battery. It takes only a minimal amount of volume to produce feedback, so battery is enough for now. But I have planned to replace battery with mains transformer, for an extra headroom. Here in Finland we also have 50hz. Signal goes from guitar ---->stompbox EQ -----> amp. Preamp? What I had in mind was some sort of buffer to take the load from pickup. What leads me to that loop? Hard to say. First I tried to eliminate that squeal with magnets. Magnet tends to excite strings too much: no result. Resistor in series with driver: no result. Piece of steel between driver an pickup: no result. Iron does just the same: no result. So nothing magnetic fits between the driver and pickup. Because the driver uses strong electromagnetic force, that is the same force we can use to create physical "bridge" between pickup and driver, so that magnetic flux doesn't float too much anymore. Instead it flows from the driver---->strings--->pickup.

Thanks for reply. My driver may look different, but there is nothing special. Amp that I use: http://www.vellemanusa.com/us/enu/product/...t.asp?id=350506. I know it's bit of an overkill for this purpose, but it works well. Only small amount of volume is needed to get feedback. What comes to that driver construction, I took some plywood and sanded it down so that it has same thickness as drivers magnet. Then routed hole for the driver. Next I placed driver in that hole and soaked it with epoxy. I used clamp to squeeze it. It needed to be flat enough to fit under the strings, so I bolted it straight to body. That black rag on right side of the driver is just a piece of rubber, used for height adjustment. So there is no iron core, only magnet. And yes, I have checked amp and all the wirings many times. But that loop thing... it is mystery to me. Even tried it with other driver, that has iron core, with same results. But it sure has some capacitive or inductive properties. Something that eliminates and/or reverses the phase of magnetic field maybe?

Thanks psw for help. So here it is: http://i247.photobucket.com/albums/gg158/u.../experiment.jpg Yep it is almost too simple but as I said, it just works. Photo of my setup: http://s247.photobucket.com/albums/gg158/u...rrent=setup.jpg That driver in neck position is made of plywood, with milled hole for the driver core. And then it was totally soaked in epoxy, that took care of potting. No microphonic behaviour available there anymore. Just singing feedback. Need I say more?

Hello there all. I have been reading this thread every now and then. I have built couple of drivers, and latest is wound around permanent magnet from an old pickup. My recent setup contains only one pickup(P-90) at bridge position, and space between pickup and driver is about 7,5 cm(3 inches). As many other readers here, I had that nasty squealing feedback, especially in harmonic mode. I don't know much about electronics or magnetics theory, so it's trial and error. One day I was tinkering again, and found out that between pickup and driver, there must be some kind of physical shunt element to eliminate cross-talking. So I took about 30 cm(10-11 inches) of solid (not braided)0,8 mm (swg 0-1?) copper wire and made a loop between driver and pickup, then hooked it in series with driver. There is very little resistance in that loop, so it won't draw too much power, and it sure doesn't excite the strings... But just enough of inductance or whatever it is, to keep driver and pickup separated. Somehow. Magically it just works, and eliminates most of cross-talking, so it is possible to put even more juice to that driver if needed. But it takes some testing, so be patient. Since my strat is in pieces right now, I have no experience with multiple pickups. If some of the readers are willing to test this, and succeed, maybe then we are able to develop better looking version of the loop. I have a primitive image of that thing, but it seems that I can't post it here directly.