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Post by 4real on Jun 25, 2007 5:33:38 GMT -5
That's a shame, I don't know if anyone could help you with this...
lucky you!
That's an excellent start. I use a blade because it is easier to make from scratch and you don't loose drive bending strings away from the poles of a conventional pickup design...it will work and an excellent place to start experimenting.
We have made drivers successfully using these things..you want to be wary though of traditional alnico ones...this thing will need to be adjusted very close to the strings so you don't want too powerful a magnetic ofce on them...a pickup with a ceramic bar under steel poles (ie, very cheap pickups...is best. What you need is a small roll of 0.2mm enamel wire...you wind this by hand, it is not fragile (like pickup wire) and you need only about 200 turns.
The "secret" of the design is you want a coil directly under the strings that is very "thin". to achieve this you need to strip the pickup wire off completely and block off the lower half or the bobbin leaving only 3mm or less to wind the new wire to. You will also need to wind this using glue (I use woood PVA glue) as you wind so that it sets solid (you want zero internal vibrations in this thing). I do have a tutorial with pics at PG when it comes back of all of this process.
It is important to understand what you are trying to achieve in basic terms. My speaker analogy is fairly good. Basically, you are taking the signal from the vibrating strings and amplifying it. The amplified signal creates an electromagnetic force indentical to the signal but powerful enough to move the strings. The pickup picks up these string vibrations and they are amplified again...so the string never stops moving (till the battery goes flat, anyway or until you dampen the strings of course).
Yes...well the whole idea is that the sustainer should run completely independantly from the guitar's signal chain...the amplifier is simply there to create the magnetic forces to keep the string moving. I say should, because it is possible for some of the driver's signal to leak back through the pickup and so enter the signal chain...but this is to be avoided.
My mid-driver for instance...is suffering from this due to the closeness of the driver to both pickups. While I am getting plenty of sustain there is distortion in the signal. Ideally these things should provide sustain completely clean (you can add distortion or effects later). For an example think of the guitar in U2's 'with or without you' (probably the only famous sustainer track. There are audio examples of my DIY sustainer guitar linked here and others at PG as well.
One of the exciting things about a variax and sustainer technology is that the variax uses piezo pickups which are non-magnetic devices. As a result, they should not pick up the electromagnetic interferance that the driver puts out to anything like the same extent, so this distortion should be nil in this application.
Aside from infinite sustain, which is all well and good...some find the appeal of this device in that it makes the guitar come alive, just like playing very loud (even if with headphones or recording direct).
There is also the harmonic effects. The harmonic function switch reverses the driver signal so instead of sustaining a note, it strives to dampen it. Instead of no sound though, it drives the harmonics...just like holding a finger lightly above a node on a string (12th, 7th, 5th fret, etc.) This greatly extends the range of the instrument by producing sounds perhaps two octaves above the played note.
If I could think of a better name for this device I would use it as sustain is only one of the reasons to be interested in this device. You could think of it as akin to a violin bow...sure with good technique a bow can create infinite sustain, but it can do much more than that for a violinist...pizzicato notes become a novelty where on guitar it is the norm! Of course, completely different instruments and effects, but you see what I mean?
Anyway...hope that makes it a little clearer, or at least gives you something to get your head around till PG comes back! You don't need to be an electronics "expert" to make this thing...you will need a soldering iron, a multimeter and some perseverance! A couple of helping hands won't go astray, chances are you will all get hooked and be making all kinds of driver designs...the more the merrier...here's hoping PG comes back soon...
pete
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disndat
Rookie Solder Flinger
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Post by disndat on Jun 25, 2007 9:50:58 GMT -5
Thanks again Pete.The pickups that I have are the cheapies so I'm good with that.I noticed that you were trying to incorporate the amp into the pickup to save space.I found this 25db mini booster circut online that would fit under the pickup store.guitarfetish.com/25migubociti.html -would this work?.I hope the guitar project forums come back so I can start this project.The whole reason I need this is I do alot of guitar sessions for tv shows and I always go direct(the composers prefer this way) so the only way to get controlled feedback and sustain is using this circut. Thanks |
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Post by 4real on Jun 25, 2007 14:31:14 GMT -5
PG is back! Come over to the main thread and introduce yourself to the others...
I am aware of this circuit and it could be good for the preamp part of the project...it won't run the driver on it's own though! It does show how small our circuitry could be if commercially built with SMD devices like that.
I am in the process of laying out my poweramp circuit for easy replication...similar to those little circuits photoed above.
see you over there... pete
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Post by 4real on Jun 27, 2007 18:41:03 GMT -5
Just another update for those following progess here... I have been doing a few tests of the mid-driver and it does work (at least on the lower strings)...but with some distortion except on lower gain settings. Ideally, you want the device to work without changing the "tone" of the guitar, and while I don't get screaming squeel...this EMI effect is not what I am really after...hmmm So...I have been exploring ways in which I might feed it with a cleaner signal...to do this I need to have more power but run it with less gain so as to reduce distortion...well that's the reasoning... My latest "little" circuit, following the theme of the mini buffer (works well) and the TDA7052 is a dual LM386 BTL amp...  This works but I fear it draws way to much power for practical onboard battery operation...still, these little circuit layouts are cute, have minimal parts and do work...here are the buffer and last amp designs I built...  The little buffer (in front of photo and layout on previous page of this thread) works and could find application in any guitar...only six components and a little veroboard! I will be making another in this series that will be a basic single LM386 amp identical to that used in my sustainer strat but layed out on veroboard or perf in a compact format similar to these. The idea is that this part of the circuit mounted directly below the driver itself. I may also try out the AGC preamp that PG member Col designed that adjusts the amount of power in relation to the amount os signal it hears...less signal, more power...once sustaining, it cuts it back. This is intended to give a more even response and saves some power in doing so. A more complex circuit (I posted it earlier in this thread) but perhaps worth it. I also had an idea for a new driver design that could fit in the 5mm gap between the neck pickup and the neck...this would need to have pickup bypassing and only work with the bridge pickup like a typical sustainer but could be built to surface mount (no routing) and be fairly inconspicuous. Such a design is now more practical given some of the techniques to build the mid-driver, so could be an interesting way to go also... pete |
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Post by CheshireCat on Aug 1, 2007 17:23:22 GMT -5
And we're back! I'm going to go ahead and test a DIY Sustainer!!
1. Will a Duncan minihumbucker coil work as a driver?
2. Got a schematic for the driver preamp?
Chesh
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setain
Meter Reader 1st Class
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Post by setain on Aug 1, 2007 20:32:53 GMT -5
1. No you can not use a regular pickup coil for the driver. The wire used is too fine and there is way too much of it; you about 8 Ohms of 32 AWG wire, instead of 8K Ohms of 42-44 AWG.
2. That is sort of in debate at the PG thread. Pete has a new one he has been working on, but is yet to share it. You can use the Fetzer/Ruby combination, as it has worked for others in the past.
Now, I have a question for Pete (should he choose to look here anytime soon): Assuming the side driver/stacked driver ideas have any merit, would it be possible to bypass only the neck pup and use the middle and bridge one?
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Post by 4real on Aug 1, 2007 21:46:05 GMT -5
Hey there...what a coincidence...haven't looked in here for a while, and here's two posts!!! So...Chesh...no you can't use a pickup for a driver...however, you can modify a pickup to be both a pickup and driver as on my original sustainer stratophasocaster thing. Exciting developments have been going on and am creating production techniques for just such a device...here is the latest incarnation hot off the new purpose built winder...    This first coil is an ultra slim version of my original single coil design...yet to be tested...but you get the idea. If all goes well I may be selling these coils in the near future...see PG for more on those plans... Meanwhile...am researching the preamp thing still...the fetzer/ruby has worked very successfully for some...I hope to develop something a bit more purpose built and will be looking at a kit of ready made circuit to go with the coils. The rail design is an interesting one for this...it could be rewound into a driver with 2x16 ohm parallel coils with some modifications...not been done yet though. Well...would you believe the last driver I made (now broken) was a side driver with 12 neo-magnets and three core fins and was ver compact. Unfortunately it didn't work to well as intended...however, tipped on it's...errr...side, in a stack...it worked surprisingly well with much reduced EMI working even in the middle position...so there is some hope for development there... If the mid-driver low EMI concept ever works, you could mount the driver in the neck position and use both bridge and middle. There are three elements to this project...the driver, the circuit and the implementation. Unfortunately the latter only gets a look in when 1 and 2 are accomplished...more work is needed here... I am hoping to develop a circuit that is simple and compact but provides some compression and limiting to avoid a runaway feedback effect and distortions...this could help. For now....I am aiming for a pickup conversion kit that is cost effective and works in a conventional way for sustainers (bridge pickup only)... I have thoughts that a superswitch could isolate the bridge pickup for the sustainer and a rotary control could select if it is on and which mode it would operate...this would provide an easy low mod way of implementing the device...but will take some work...will be looking for advice when it gets to this part... I have a new innovative design for low EMI that goes with this concept that I hope may replace this primitive single coil design. I have made a machine and developed a technique to make such coils quickly with no bobbins or metal work...the above is the first coil from it, so they can only get better. The new design relies on similar techniques and both are near impossible to make without such a machine. If all goes well everyone will benefit from me making such coils and possibly even the circuits. Imagine if you will, a sustainer that is fitted by replacing the cover of the pickup with one with such a coil built in...getting closer everyday... pete |
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Post by 4real on Aug 3, 2007 5:49:19 GMT -5
;D Just a quick update, the ultra thin coil pictured above appears to be working perfectly, better than the original and on a stock (squier) single coil stagered alnico pole pickup without modifications and completely reversable...
Ok...so I'll try and keep this on a role... pete
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Post by CheshireCat on Aug 4, 2007 2:13:31 GMT -5
It's an individual mini-humbucker coil. I made a thin single coil to go above the intended sustainiac driver, to try and recoup some bassiness, since at the time the proper pickup had been moved so far south.
Then it occurred to me . . . if I can turn that thin single coil into a driver, then I can just bring my old Seymour Duncan Jeff Beck back, and then everything's gravy.
The coil is from an old Lil'59, and as such had a bar magnet, blade, and six lug pole pieces (machine screws) screwed into the blade. Would this be adequate, assuming that I rewound it appropriately, or do I need a straight-up blade pickup?
Also, do you have a copy of the Fetzer/Ruby schematic, or perhaps pics or diagrams, so I can breadboard it and test it out?
Chesh
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Post by 4real on Aug 4, 2007 5:16:11 GMT -5
Chesh OK... Ok...you need to block off the lower half of the bobbin to make a thin 8 ohm coil of 0.2mm wire on top, well potted. Go to the main thread at PG and on any of my posts are links below to a range of tutorials and such with the information you need on it... Also, do you have a copy of the Fetzer/Ruby schematic, or perhaps pics or diagrams, so I can breadboard it and test it out? Better yet, have you seen the fabulous software called DIY Layout creator? Go to this page www.storm-software.co.yu/diy/index.php?project=layoutsfor a circuit layout of the F/R (you'll need to download the free software to read it)...and this page www.storm-software.co.yu/diy/index.php?project=sustainerThe links are also at the bottom of his page too! This would appear to be exactly the kind of thing you are contemplating...yes? The direction I am presently returning to is pickup conversion to have a simple reversible way to adapt a pickup into a driver. I am working towards circuit improvement. Specifically, the thing could benefit from some limiting of the signal based on some kind of feed forward type of design. This is a pretty unusual kind of circuit, you want the circuitry to compress and limit according to what the string is actually doing, not what the circuit thinks it has done to the signal...high string require a little more power for instance, you don't want to cut back on power because it has reached an arbitory threshold based on the amps output...subtle but significant in this application. The basic amplifier design though does work fine though, just a little less refined than I'd like. The problem is also balancing complexity with practicality...Col's circuit posted here does something like this, but requires quite a few opamps and assorted supporting components to achieve it...debatable as to whether it is overkill or not... anyway...always best to start off with the simple circuit and with a simple test coil held above the strings before you get to carried away. Most need a couple of goes at the coil, though many have been successful first go... pete |
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Post by CheshireCat on Aug 4, 2007 22:05:02 GMT -5
So far everything looks cool!
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Post by 4real on Aug 8, 2007 16:07:12 GMT -5
A bit more of an update...
I have tried a few alternative designs, but am settling for now on a simple ultra slim epoxy wound coil from my new driver winding machine.
This coil is built to stick to the top of a strat neck pickup and hopefully will work with the cover on (otherwise I will have to modify covers fro the purpose)... This driver is working perfectly on all strings (with a '10 set), even better than the original and two thirds thinner...only 1mm thick
The next step is refining the circuitry...I already have ideas. It needs to be very simple and small of course. Ideally I'd be looking for a kind of forward feed limiting circuit to avoid excessive drive and EMI before the strings reach their ultimate vibrating potential.
Following that will be working out the bypass switching to make this an easier failsafe procedure. This is tricky and I will no doubt be back asking for advice and opinions when it gets to this stage. What would be really cool would be a pot that controls the harmonic drive in it's sweep...combine that with a pot-switch and you'd have a fantastic no-mod installation. Unfortunately, only the S-1 has the kind of switching power (4pdt) that I'd need to achieve this. Perhaps there is a way to simplify it with a push/pull dpdt switch, or maybe combine such a switch with a super-switch so that the pickup selection only occurs when the bridge pickup is selected. It's one of the trickier parts of the project and often overlooked...
Hopefully, the end result will be a small time supply of coils and circuits. The aim is to make a reversible mod to the pickup and a simple, small and cheap kit that people can be assured will work for them (on strat pickups for a start)...
This shouldn't kill experimentation though, the circuit could be used for peoples driver experiments or the driver used to develop circuit ideas...at the very least it would make a good jumping off point.
The pictures of the driver above show the kind of direction I am going with this venture...wish me luck!
pete
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gunther
Apprentice Shielder
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Post by gunther on Aug 8, 2007 16:46:33 GMT -5
Cool. I'm definately interested in one of these as i love playing with my ebow.
Do you make any for others?
Cheers
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Post by 4real on Aug 8, 2007 17:28:11 GMT -5
Yes...well not yet but soon. As with all sustainers there is a bit of installation to contend with. This idea though allows a minor addition/modification to a strat pickup rather than the complete replacement of it with a driver.
There are a lot of similarities to the ebow but a sustainer has the advantage of keeping your technique and working on all strings. Damping of strings becomes very important as it is much like playing with a very loud amp!
The down side has always been the modifications required to install this type of device and the cost and lack of support.
The DIY sustainer works well enough and even has advantages over the commercial systems. My new approach...modifying the pickup with my trademark thin coils, takes it another step further. It should also work out a lot cheaper!
Still...a little more ways to go yet. So far, I have developed the technology to produce the coils which many find difficult to construct with accuracy, even finding the wire has been tricky for some.
The circuitry, finding components and making the circuit has been a problem. There have also been a variety of circuits but few purposely designed for this project. I have been working on this for a bit and if a universal design can be hit upon, they could be made as a kit or assembled by me...or with sufficient interest made in small quantities on PCB, possibly even using SMD components!
Anyway...one step at a time, for now circuit development and consideration of installation procedures. This type of driver will only work in the neck position with the bridge pickup, all other pickups must be completely removed (both hot and ground) from the guitar's signal chain and the bridge pickup selected, plus the power turned on...that's a lot of switching! Additionally you will want a harmonic switch function but other modes are also possible that range around the "mixed modes" of operation between fundamental and harmonic modes.
Previous sustainers have provided a sensitivity control (drive gain) but I have not really found this to be that useful (it can be controlled by picking strength to some extent) A harmonic control dial would be a fantastic development for usability of the device.
Any assistance on circuitry or installation issues would be greatly appreciated and help things along...
pete
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Post by CheshireCat on Aug 8, 2007 21:23:17 GMT -5
Yes...well not yet but soon. As with all sustainers there is a bit of installation to contend with. This idea though allows a minor addition/modification to a strat pickup rather than the complete replacement of it with a driver. There are a lot of similarities to the ebow but a sustainer has the advantage of keeping your technique and working on all strings. Damping of strings becomes very important as it is much like playing with a very loud amp! The down side has always been the modifications required to install this type of device and the cost and lack of support. The DIY sustainer works well enough and even has advantages over the commercial systems. My new approach...modifying the pickup with my trademark thin coils, takes it another step further. It should also work out a lot cheaper! Still...a little more ways to go yet. So far, I have developed the technology to produce the coils which many find difficult to construct with accuracy, even finding the wire has been tricky for some. The circuitry, finding components and making the circuit has been a problem. There have also been a variety of circuits but few purposely designed for this project. I have been working on this for a bit and if a universal design can be hit upon, they could be made as a kit or assembled by me...or with sufficient interest made in small quantities on PCB, possibly even using SMD components! Anyway...one step at a time, for now circuit development and consideration of installation procedures. This type of driver will only work in the neck position with the bridge pickup, all other pickups must be completely removed (both hot and ground) from the guitar's signal chain and the bridge pickup selected, plus the power turned on...that's a lot of switching! Additionally you will want a harmonic switch function but other modes are also possible that range around the "mixed modes" of operation between fundamental and harmonic modes. Previous sustainers have provided a sensitivity control (drive gain) but I have not really found this to be that useful (it can be controlled by picking strength to some extent) A harmonic control dial would be a fantastic development for usability of the device. Any assistance on circuitry or installation issues would be greatly appreciated and help things along... peteFirst off, sign me up for the first one. Second, hmmmmmmmmm . . . ya got me thinkin'. |
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Post by 4real on Aug 9, 2007 7:10:45 GMT -5
Well that's some interest for a start... There is still a bit of work to turn this into a "product" but so far all is going well. I have been mucking about with the latest coil and it is a big improvement over the original using the same circuitry and guitar. I have been doing quite a bit of research on some circuits and have made a prototype board today, so the circuitry is well on the way. I would like to make a significant improvement without getting complicated and I believe this is possible. If it all becomes a little hard of course, we know that a simple amplifier circuit like the fetzer/ruby or the circuitry I use (high gain preamp) works well. Basically we are looking at a LM386 amp with a preamp or buffer. The improvements I am seeking is forward feed limiting...this will help the amp respond to how hard the string is actually being driven rather than how hard the amp thinks it is being driven (thin high strings require more power for instance, and the bass strings need to be toned down a little). The device may even benefit from compression, though it seems to work quite well without it. Col has shown that it would appear that such automatic gain control will actually make the battery life longer as the driver isn't pushing so hard all the time...it's main purpose is to add control and improve response caused by string gauge, mass and the effects of the guitars "action" pushing the string closer to the driver as it is fretted by varying amounts. Col's circuit, posted earlier in this thread, does work but uses 4 opamps just in the preamp with a lot of supporting components...this would be impractical for my purposes and am sure there is an easier, good enough approach. Even as is, these things are minor issues and the device works well in it's prototype form...I actually wouldn't want it tamed too much! This coil is such that I get harmonics in the fundamental mode and higher harmonics in the harmonic mode. With the original coil I had to put a fair amount of treble bias into the circuit to get the high strings to respond well, the result was a pleasing fundamental into fifth above harmonic on the lower strings. With this new coil, the resonant frequency will be different and so less bias must be needed. Of course, the response of the pickup driving it will also be a factor. Ideally, I would like to do away with as many trimmers and such and have a simple compact one-circuit-suits-all solution (fernandes and co have 4 trim pots to adjust for response). Given the range of harmonic responses possible by altering this bias, it may well be possible to make a "harmonic control" pot...another unique feature of my device...now if I can just work out how to turn the thing on! The guitar I am testing it on has a stacked single coil in the bridge position, the guitar I am going to install it on first is a SD JB HB. This should cover most bases. There could be an issue with some cheap strats that have a narrower string thread as the coil may not fit under these covers...tele's may require a narrower coil with a bit more depth to fit...that will be another issue. 7 strings should work too, but I would need to make a new jig to wind such a coil... HB's will require two coils and different specs...Avalon has shown that it would work, but how it could be done with my concept is another matter, for another time... As will a bass version, for this, a separate driver is probably more appropriate, but it would need a different circuit that could handle the lower frequencies and special driver for pickups such as that on a P-bass which is split between the string sets. For the time being then, it is strats, unless you want to make your own...  Oh...and by the way...very light strings, .9's will not respond I fear and you may have to change up a set to 10's otherwise your high string will not sustain... So...all good and coming along...stay tuned... pete |
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Post by 4real on Aug 10, 2007 4:58:35 GMT -5
So, here is my latest post over at PG...but in it is some questions possibly more appropriate to you guys to ponder over....(see highlighted bit below)So...you see after extensive work, this "product" coming together. Now I am up to the tricky question of installation. The circuit is pretty small, and in Strats you tend to be able to find room for the battery in the trem cavity (it needs to be easily replaced with this device so can't really go under the pick guard). Potentially, even the circuit could go in there too! As with any sustainer, you pretty much have to rewire the guitar. Even though I only recently did this for the mid-driver experiments...thanks to John and all who helped with this...but now I am getting to the nitty gritty. This driver design is simple and very effective, the circuitry small and devoid of too many "tricks" or any fancy components, though it is not your typical preamp/amp (has compression and limiting built in ). The thing fits in easily with no mods... As quoted, I was thinking of a super switch with the following selections... neck pickup~ neck and middle~ neck and bridge~ Sustainer bridge~ Bridge HB pickup~ Master volume and tone... The sustainer selection must completely disconnect both other pickups (both hot and ground of the coils) to avoid noise. I am prepared to add a small tactile switch to switch on power in the sustainer selection of the super-switch...a small protrusion should easily activate that, but can it cope with the other requirements? As for the rotary control...a normal push-pull DPDT is enough to reverse the pickup (effecting the combined settings) or the driver leads, but using this pot as a harmonic control will require some inventiveness. Basically, the smaller the output cap, the more mixed the harmonic response. I use a 100uF cap that gives a harmonic bloom (up a fifth) to the lower notes. A 220uF gives a pretty strong fundamental to the low strings, but then the higher strings are less responsive. Similarly, in harmonic mode, such alterations in treble bias produce a wide range of harmonics and response that coul be useful. What would be really cool would be a turbo mode in the extreme setting, or perhaps this would require another switch...increasing the gain to just before squealing does produce distortion, but then it also makes wonderfully strong feedback and harmonic effects. Building this into the same control is probably a bit of an ask, it is almost asking for a joystick control...hehehe Anyway...hope you guys can put a little input into this, I have a much better idea of how the super-switch works after the last time, so the mechanics wont be so much of a problem, only the logic... Thaks in advance... pete
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Post by sumgai on Aug 11, 2007 2:03:18 GMT -5
Pete, One or two things about what you said above.......... This is emminently do-able. There's no reason why each pickup can't be assigned to one of the switch sections, and the Sustainer can be controlled (i.e., powered on/off) via the remaining section. Do you want me (or any other member here) to draw up a schematic for you? Errrrr, not quite. No disconnection of the ground side is necessary. If it was, we'd: A) see this happen in absolutely every (quality) guitar ever made - the fact of any such necessity would have shown up by now; and B) be in strong violation of every known principle of electromagnetics. Anything that "gets" into the ground is, by definition, dead meat - we won't be hearing it any time soon. That's why we call it "ground", and not "return side of the circuit" - it's gone to the Mother of All Sound Absorbers!  If you can hear, through the amp, noises from the Sustainer being picked up by a coil hooked to the ground only, then your wiring needs to be re-checked! Not necessary, see the first answer above. Whoa! Those are some mighty big capacitor values here, podner! I gotta believe that you meant to type in nano-farads, not µ-farads. Those values would be effective in the sub-sub-sonic range of frequencies, given the inductance values you're playing with. Just some observations. sumgai |
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Post by 4real on Aug 12, 2007 4:25:59 GMT -5
Thanks Sumgai...I thought you guys might be getting sick of me popping up and asking these questions...am bogged down at the moment just getting the thing to respond properly...making good headway...
That would be great if anyone has the time...however...
Well..it could be from the battery connected to earth and drawing so much current to drive it that causes the noise...but noise there is. I believed that it wouldn't be necessary but found no other solution...also, had the feeling that the pickups were acting as antenna and transmitting noise from the coil, through the ground to the bridge pickup and from there to the hot of the guitar's output...similar to a transformer coupling effect...but I must admit to not understanding this phenomena myself...
Well..if it is possible, then great...but I have a suspicion that more switching could be required...see what you guys can come up with...switching logic is not a strong point...the tactile switch for power on is an option if necessary...
Actually I do mean u-farads...we are talking a mini power amp here, not a signal processor...you need this kind of cap to get any kind of bass response on the output cap...also, the thing is putting out a few volts, about half a watt of power, so a few of the caps need to be this kind of size unfortunately...it's a miricle I have a circuit as small as I have...check out circuits like ROG's Ruby or any other LM386 type of circuit...
An amusing side note...so I made one particular circuit that I am pretty happy with...then I find an error in my layout and so, it isn't doing what I intended it to do...I rebuilt it as intended but it wasn't anything like as good...so now I have to try and figure out what went right on this one...it looks like there are a few redundant components including two trim pots...so this thing may get even simpler and smaller as a result! I'm not one who easily gives up on my failures...hehehe
Better run, but appreciate the interest and if anyone has a mind to look into this or have some other ideas...(seems a bit strange to have only one positon where the mid-pickup is used, and then only in combination...oh and the bridge pickup is an HB (JB) suitable for splitting if that is of any help)...I'd be most interested...more hands will lighten the load!
Thanks in advance... pete
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Post by sumgai on Aug 16, 2007 4:29:33 GMT -5
Pete, Here ya go, as promised:  Pretend that the Bridge single coil is your humbucker. Since you didn't mention anything about splitting, putting it in series or parallel, or whatever, I simply redrew a previous schematic with the necessary switching changes, and didn't bother to draw up a new dual-coil pup.  You'll be happy to note that I was able to snap off both ends of the Neck and Middle pickups when the Sustainer goes into action. While I still don't believe it's necessary, I can't see any legimate objection, so I did it anyway. Absolutely not true. The fact that you have a power amplifer instead of a preamp (or what you called a signal processor) has absolutely nothing to do with it. Nor do the voltage/current/power levels, all of those are indicated by the ratings on the cap itself, but none of them are directly concerned with the actual capacitance value. In short, frequency doesn't care about how much power is being developed, it's independent of all that. By way of example, look at any home-stereo hi-fi amplifier, or even our own guitar amps - you'll find the same values of capacitance (within a small range) no matter which end of the circuit they are located in. The only differences will be the voltage handling rating, and that is directly concerned with size, just like capacitance. In point of fact, if you'll look up the various formulae for selecting capacitors to either pass or block certain frequencies, you'll find that a 10µf cap pretty much covers the entire audio spectrum, right down to 20Hz. What you'll get with a 220µf cap is essentially the ability to pass all frequencies above approximately 1Hz - not quite DC, but purty close. Do you really need that capability?  I think that if you are exciting the coil by amplifying and feeding back the initial string signal, and you need this large a capitance to make it work, then there's something else going on here of which we are not yet aware. So ends today's diatribe. ;D HTH sumgai |
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Post by UnklMickey on Aug 16, 2007 12:08:35 GMT -5
...Actually I do mean u-farads...we are talking a mini power amp here, not a signal processor...you need this kind of cap to get any kind of bass response on the output cap...also, the thing is putting out a few volts, about half a watt of power, so a few of the caps need to be this kind of size unfortunately...it's a miricle I have a circuit as small as I have...check out circuits like ROG's Ruby or any other LM386 type of circuit... Lemme see if I can get us all on the same page here. This output cap would be in series with the sustainer coil. Remember this is not acting as "microphone" it's functioning like a "speaker". It's the load. It's impedance is probably in the tens or hundreds of ohms, not 100k ish loads like we're accustomed to dealing with. The roll-off (-3dB) will occur when the capacitive reactance of the cap in series with the load is equal to the impedance of the load. |
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Post by JohnH on Aug 16, 2007 15:43:35 GMT -5
Yes, Id agree that a large output cap is needed - as on the output of most transistor amps that drive speakers.
John
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Post by sumgai on Aug 16, 2007 15:55:17 GMT -5
Lemme see if I can get us all on the same page here. This output cap would be in series with the sustainer coil. Remember this is not acting as "microphone" it's functioning like a "speaker". It's the load. It's impedance is probably in the tens or hundreds of ohms, not 100k ish loads like we're accustomed to dealing with. The roll-off (-3dB) will occur when the capacitive reactance of the cap in series with the load is equal to the impedance of the load. Always a good idea, as per the usual high standards of The Unkster. I use this formula to derive capacitance values for a given frequency: C = 1 / 4π 2F 2L (That reads as "c equals 1 over four pi squared times frequency squared times inductance") Note that inductance is not the same as impedance. We all have those impedance numbers stamped in our heads, but it's inductance that counts most. Accordingly, we need an inductance figure before we can go any further. But that gets involved and deeply mired in electrical theory, so let me shortcut it way down to basics - a speaker's nominal inductance is, happenstancely, 8 to 10 henries. For purposes of our discussion here, I'll treat 4pete's sustainer coil as having the same properties as a speaker, and therefore it should exhibit about the same inductance value. Returning to the forumla, we can now plug in all the necessary numbers. We'll assume that a guitar's lowest frequency is an open E, or about 81.something Hz. We need to pass that frequency in full force, and the formula calculates a 3dB rolloff point, also defined as the half-strength point. So let's drop our frequency to 40Hz, and at 80Hz, we should be at full strength. Plugging in the numbers: L = 10 F 2 = 1600 (40 squared) 4π 2 = 39.48 Multiplied together, we get = 631,680 Inverted (the "one over" statement) = 0.000001583 Therefore....... C = 1.5µf, giving us just enough passage to pretty much guarantee full signal strength at the proposed 81Hz. Unless other constraints apply, we always "fudge" this value a bit, so a 2.2µf cap would probably be best here. Note: at no time did voltage, current or power come into play here. Frequency is simply a measurement of how often a tone cycles from zero strength to full strength and back, and neither voltage or current affect that measurement. In basic terms, of course. ;D And yes, I have played a bit loose with the inductance factor, but consider...... even if the factor is off by an order of magnitude, in either direction, the equation will still skew only one decimal place, in the appropriate direction. 4pete's chosen values of 100 to 220µf show that the inductance must be literally a small decimal fraction of a henry. With an iron core in the gap, I'm gonna have to refuse to believe that one, it just ain't in the cards.  Further research on inductors and inductance is an exercise best left to the reader. ;D HTH sumgai p.s. (added this as an edit....) It seems to me, upon several minutes reflection, that some folks may balk at my use of inductance. I need only ask, where do you think impedance comes from? Assuredly, it is a complex number (a force vector, right up ChrisK's alley) that comes from both the straight-ahead resistance of the wire in a coil, and the inductance of said coil. I always feel more comfortable with using the most basic building blocks. |
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Post by 4real on Aug 16, 2007 15:57:35 GMT -5
Thanks Unk, superb... Having thought about it, I could see it would be possible, this will save a lot of time trying to nut it out for myself. As for the cap...the LM386 and all amp circuits using it use quite large output caps to preserve the bass response... www.national.com/ds/LM/LM386.pdfI typically use a 100uF to get a balance between low and high string response. 220uF will give better bass, but not so necessary with this, I have seen 470uF specified. In my prototype "magic" circuit I have a rotary control that ranges from a clean very controlled but lower than the original note, infinite sustain. Higher setting give a reedy distortion effect and more power and maxed out a full on distortion and screaming feedback response...all of this through headphones if desired. Still working on the circuit and variations, but if I work it too much it will take a long time to get the thing out to others. This super switch with a push-pull pot would be ideal. The push pull operates the harmonic/fundamental modes. One problem that you may be able to assist with, this rotary control requires a 1k linear pot, is there a way to adapt a different value of pot to work at this value, I think a 1k push pull is going to be hard to track down and precludes the use of existing pots for this purpose...rats... I think I heard of some technique of putting a resistor across a pot to change its value... Large caps do make things a bit bigger, but since there are few components, for these larger ones I am experimenting with some SMD and Tantalum caps as replacements... Anyway, this scheme will make things a lot easier and will rewire the guitar accordingly as soon as this circuit is complete. The only phase, or series combinations at this stage could be with the middle selection. The mid pickup is an obsolete kind of sound, this scheme gives the classic strat neck/middle sound so the bridge/middle seems not so important and can sound a little thin. On this guitar, with a bridge HB, it doesn't quack anyway. whether the middle selection would be more use as three pickups on, series, split HB or OoP is up for debate. Anyway...fine work and just in time... petePS...I take it there will be some takers for an affordable low mod s*stainer kit from this site when it is fully developed? |
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Post by sumgai on Aug 16, 2007 16:34:16 GMT -5
Pete, Not to put too fine a point on it, but if you'll look very carefully at each of those schematics (in your link), you find that the output capacitor is actually part of a divider network. The value is so high in order to create a favorable ratio with the grounded capacitor, not because it's needed to pass a given frequency. Voltage dividers do. In point of fact, the cap is necessary to prevent (block) DC from getting to the next stage or device in the signal chain. But once that's present, then the grounded one is needed to compensate for the phase shift introduced by the series cap. Ugly, but tenable. Best would have been to eliminate the DC offset on the output line right inside the chip in the first place. HTH sumgai |
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Post by ChrisK on Aug 16, 2007 18:47:20 GMT -5
Bear in mind that your 40 Hz example (10 H and 1u5F) also (perhaps inadvertently) has a resonant frequency (as in oscillatory peak) at 40 Hz. For relatively even frequency response, one would want such peaking to be outside of the frequency band of interest (unless you're looking for a boomy bottom end in a bass reflex sort of way).
Based on the drive results as a function of capacitance, this peaking is being used to realize the preferred response.
Fr = 1/(2pi(LC)^0.5)
1/(2pi(10 * 0.0000015)^0.5) = 41 Hz
The error induced by an inductor value off by a factor of 10 either way is really the square root of the error.
1/(2pi(10 * 0.000015)^0.5) = 13 Hz
1/(2pi(10 * 0.0000015)^0.5) = 130 Hz
As one can see, an error of 100 equates to an actual shift in Fr of a factor of 10.
Knowing the inductor values (Henry's and Ohms) would enable easy modeling of the voltage induced across the drive coil. The inductance and capacitance set the resonant frequency, the resistance sets the Q or broadness of the peaking. And then there's the driver stage to model also.....
I suspect that we're looking at a coil that might be 100 mH and maaaaybe up to 1 H, maybe. An 8 Ohm guitar loudspeaker coil is maybe 0.5 to 1 mH.
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Post by 4real on Aug 17, 2007 3:51:32 GMT -5
Wow...great stuff...
I don't know how I can uses it...I chose the 100uf as a result of substituting various caps, phase is important as you want the drive to be as close to the physical vibration of the string to get the most efficient drive.
The driver can be looked at as a speaker, exactly how I can determine it's inductance is beyond me at present.
I am seeking a circuit that works (for whatever reason) and will be seeking to refine it further for a mark 2 version at some point. The output cap was chosen completely by trial and error over very many experiments with this device. With some sustainers there is a mix setting between harmonic and fundamental modes (mine tends to operate in this mode on the low low strings in fundamental mode)...this seems to be chosen by adding a 10uF cap to the circuit.
The commercial sustainers us a far more complex circuit than my device with phase compensation, ACG and more...my designs have always tried to address these issues with driver design...my new circuit does have some limiting now to avoid the response completely running away, also this should extend battery life.
I have since kind of abandoned this variable capacitor idea mentioned earlier, for a unique, more gain/compression type effect. This has been prototyped and would be given as an optional offboard control, or equipped with a trimmer on the board, a set-and-forget install...
So...better keep at it and thanks for the input, every bit helps, and that wiring diagram will really help things along...any ideas on pot conversion or a switch pot of 1k ohms?
pete
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Post by sumgai on Aug 17, 2007 4:05:06 GMT -5
Chris, ...........
An 8 Ohm guitar loudspeaker coil is maybe 0.5 to 1 mH. A milli-Henry coil with that much metallic mass in it? This I gotta see. It's late, I'll go do some more research on-line tomorrow..... see if I can't find a definitive source on that particular topic. Oh, that 40Hz resonance? It is outside the frequency band of interest, by about an octave. Might not be enough, of course, but for a first approximation.........  sumgai |
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Post by ashcatlt on Aug 17, 2007 16:05:11 GMT -5
I've been looking forward to this product, can't wait till I can purchase a simple, plug and play, non-permanent sustainer solution. For a while there that's what I thought you were talking about. Now I'm not so sure. You're talking about re-wiring your guitar to make it work and all that. Any reason it can't just be a coil and some little box that hangs on the guitar strap or somewhere similar (maybe like the box connected to the roland hex pickups?). I understand that certain pickup selections will not work or give pleasing results for one reason or another (noise, etc) but can you not just include a warning in the packaging/installation guide/owner's manuall pointing these things out? As you're seeing, trying to rewire your guitar to accomodate the sustainer forces you to make tough decisions re: pickup selections/combinations. Some of us have worked (or made others work ) very hard to come up with the wiring that we find most intuitive and useful for our style. If I have to throw all of that out in order to use your circuit, I won't. Besides that, some whacko might actually use the "wrong" pickup selections for special effects. Oh, and have you put any thought into a version compatible with rail-style mini HBs? What about Ric "toasters"? Thanks edit - i can spell, really i can.... |
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Post by 4real on Aug 17, 2007 17:48:39 GMT -5
Now Firefox has auto spell...so can I truuuely... I note your concerns ashcatlt... This system is a lot less invasive than any other proposed system so far...that said, there will always be a need to comprimise... The problem with wrong pickup selections is not that it makes an unpleasing noise, it makes the guitar unusable even in other modes of operation, not just noise and distortion but high frequency oscillation that masks all of the guitar's signal... That said, if people wanted to misuse my device to create such effects or to develop it further, I am encourging people to do so...the more people working on it and various installations, the faster progress and innovations will come. That is the reason for the very long (200+ page) sustainer thread at PG. The solution for you is to install the device with a separate toggle switch as I did on my original guitar...see the early posts on this thread. A 4pdt switch can be used to deselect all pickups and connect the bridge pickup no matter the pickup selection and turn on the power... Any other variation could be done at your own risk...no harm will come of anything except a lot of frustration...believe me... The box idea was something I really did pursue but extensive manipulation of the guitars electronics will need to be utilized anyway...here is a realization from a long time ago of the kind of thing we envisaged...  I was also trying to make bridge mounted systems but there are seemingly insurmountable problems and I really did over-reach myself with some of these pursuits... Kids wont let me stay right now...and this will be a mark one version...other driver models are likely to follow, in particular rail and HB models (a fair amount of work has been done along these lines) but these will not be quite as simple to make or install...for now it will be the single coil or stacked type pickups... later... pete |
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If you can hear, through the amp, noises from the Sustainer being picked up by a coil hooked to the ground only, then your wiring needs to be re-checked!
