Jump to content

Recommended Posts

Thanks LK, I had kind of seen that over there but not had a good look....it is pretty neat and ideal for modding into something for this by the look of it...still need a preamp and stuff. I actually built a limiter/compressor with a LM386 stage in it as a preamp/amp to test stuff for this project...as seen in this fuzzy picture on the chair...the thing with the green knobs on!

sustainerstrat.jpg

Worked well but obviously a bit big and expensive to build into the guitar. I suspect that there is already plenty of clipping compression anyway with a hot preamp like mine into the LM386 and the resulting sustain is probably just as good.

Interesting circuit mod there for the switching/installation...not sure what is going on there with the 100k resistors to ground, care to elaborate on the principle? For sure, there is more to be explored on the installation front...

I had an idea for a surface mount driver that could be used on a semi-permenant basis with a few different guitars, and I think the bobbinless driver is a natural canidate for that sort of thing.

We really explored the temporary driver idea a fair bit and the idea is great, but I now question it being at all possible...but you never know. Followers of this thread will recall that as my driver designs got smaller we started looking into the idea of a surface mounted box and driver for the whole thing mounted like a tailpiece...but, there will always likely to be significant wiring changes to achieve bypassing so a temporary install is a bit of a dream I think.

What is achievable would be an extremely low to no(permanent)mod install, especially with surface mounted elctronic switching, SMD's and remote power. But even this has some problems...a lot of guitars have their pickups right up against the neck (LP, Jem, PRS) and as a result there is no room to mount a driver in that kind of location. You will also need some kind of height adjustment. Both of these factors favour the modification of the actual neck pickup or it's replacement. A single pickup guitar with dedicated driver has a lot going for it too, if people are making a purpose built instrument.

I am really not sure why the driver seems to be presenting problems for you guys....I do wonder if the test amps may not have something to do with it. It could be that you are not providing the right kind of amplification for this driver and that is resulting in problems that wouldn't be so bad with a low powered battery driven device like mine.

pete

Link to post
Share on other sites
  • Replies 4.7k
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Popular Posts

Hello again...just looking in after moving to my island...getting a bit chilly down here! Good to see the thread continues the tradition of long threads! Still...the computer didn't survive the mov

Excellent... This will be great, and I hadn't thought about that but the 4 ohm coils would take half the time and be easier to wind....alowing the use of quick epoxy like this...hope you wore rubbe

hi everyone:

here's the deal: I'm willing to go through and experiment with all of this stuff, but i want to try to understand it first. I know how electromagnets work KIND OF, and by kind of I mean the basics. What I'm having trouble with, just because I don't understand it, is why put magnets under the steel core? I have a small steel core and some wire ready for winding, but I'm wondering what magnet configuration makes the most sense, if it matters at all, and above all else, WHY???

~P

Link to post
Share on other sites

Hi petegroh, welcome to PG and to the Sustainer Thread...

OK...you might think that you wouldn't need a magnet, as the coil of wire makes an electromagnet...

Interestingly, I was poking around DIYstompbox the other week, when I saw LK's previously mentioned circuit BTW, but also looked at some old sustainer threads...here's a link to one I had found from 2003...Making A Sustainer...

Here is an explanation from there...

R.G.

Guest

Re: Making a sustainer

« Reply #5 on: January 02, 2003, 10:24:35 AM »

--------------------------------------------------------------------------------

(a) There has to be a magnet in the driver; permanent or electromagnet, either way. The steady pull on the strings lets the driver relax the pull in one direction and increase it the other to get steady oscillation.

(:D Andrew's right, it takes a lot of energy/work to move a string. The secret to using a pickup-style device to be a sustainer driver is that the voltage needed to drive the pickup goes up with the number of turns. A stock pickup with order of thousands of turns needs order of hundreds of volts to drive the string. Worse, high turns number makes for high inductance, which limits the high frequencies that the driver can do - you can't turn the current on and off fast enough because of the inductance, and it's the current (ampere-turns actually) that causes the magnetic field to move the strings.

Workable sustainers use low turns to get high frequency response and low voltage drive. A coil with around 200 turns of #24 ('stat about right, Mark?) is reasonably suitable for a 9V powered 386 driver in a strat-pickup style bobbin. There was a discussion on sustainers a few months back in the pickups forum over on ampage.

© power from batteries is a problem. The later built-in sustainers use Class D amplifiers to wring out the most battery life.

(d) is my own fillip, which to my knowledge no one else has come up with. A 200 turn pickup coil is pitiful in terms of how much output it has. I think you could do one of two things to get dual use as both a sustainer driver and as a pickup out of it. One is to just use a very, very quiet high gain onboard amplifier to boost the low signal back up. The second is to use a stepup transformer, similar to the arrangements for moving coil LP pickups, to get more level out of the thing.

R.G.

So, I tend to think of the magnet as providing a bit of grip on the string that is tightening and loosening on it...but you do have to have some grip on it to get it to move. That is what the magnet is for...without it it would be like picking the guitar by waveing a plectrum at the strings rather than physically striking them!

As for the type of magnet. You need to have the core with the same polarity across it, changing the polarity is the equivilent to changing the wires around which will produce the harmonic effect. You cant then use a magnet which has the poles on either end but one that is magnetised along it's length as in a pickup magnet. You could however use a number of smaller magnets arranged so that all the polarities are facing the same way. You don't need any special type of magnet, you don't want it too strong that it effects the strings vibrations...you can use exotic magnets like Neodyminium/Rare Earth magnets but they will have to be very small (possibly an advantage) and could be tricky to find. If the driver is going to be made with a conventional pickup as I have done and fookgub is trying...there is no need for magnets as the pickups own magnet is enough.

Hope that helps... pete

Link to post
Share on other sites

Worked well but obviously a bit big and expensive to build into the guitar. I suspect that there is already plenty of clipping compression anyway with a hot preamp like mine into the LM386 and the resulting sustain is probably just as good.

I haven't been able to hook it up to a real coil yet, but my tests on the Ruby-Fetzer indicate that there is going to be a substantial amount of clipping. I may try the compressor if I can dig a suitable MOSFET out of my parts bin, but I have a feeling it's not going to add much. Unfortunately my oscilloscope is so old that the only way to get a screenshot is to take a picture of it. Otherwise, I'd post a few images of the waveform.

Interesting circuit mod there for the switching/installation...not sure what is going on there with the 100k resistors to ground, care to elaborate on the principle? For sure, there is more to be explored on the installation front...

The resistors are there to keep the pickups referenced to ground when they are not selected. This prevents pops when switching pickups. Imagine replacing the resistors with open circuits. You can see that each pickup that is not selected is completely out of the circuit. So when the bridge pickup is selected, the neck and middle pickups are not connected at all. I believe this replicates what you're doing with the automatic bridge pickup selection, except that it's not automatic... I still have to make sure the bridge pickup is selected before turning on the sustainer. The upside is that the wiring is much simpler, and there is no need for exotic 4PDT switches.

I am really not sure why the driver seems to be presenting problems for you guys....I do wonder if the test amps may not have something to do with it. It could be that you are not providing the right kind of amplification for this driver and that is resulting in problems that wouldn't be so bad with a low powered battery driven device like mine.

That is probably an issue, but I think the bigger problem is that I still have not been able make a coil that isn't microphonic. I came close with the last one I did on the Lace bobbin, but broke it before I could do any real testing. I think that Lace bobbin is ruined now, too. I spent some time trying the cut the coil out last night and it's not going to come out without some real effort. This is why I'm staying away from epoxy for my pickup/driver coil. Also, I may stick the coil that I potted in Loctite in a vacuum sometime and see if I can get the Loctite to set up. Obviously this isn't a solution available to most DIY'ers, but I'd at least like to see if it's workable.

I spent some time looking at Class D stuff the other day. I was hoping to find an integrated IC, similar in application to the 386. Such things do exist, but they're intended for cell phones, mp3 players, and other small devices. The form factors are small. A discrete design is about the only way to go, but a PCB would still be required since the potential for unwanted EMI is high and the lead layout would need to be done very carefully.

Anyway, for those that are interested, a Class D amp like what we would want needs 4 basic things: a triangle wave generator, a comparator (for PWM generation), an output stage, and an output filter (filterless designs exist, but I don't think that's an option in our application). The first two stages could be implemented with a quad comparator and some various passive components. I think the best way to go for the output stage is to find a suitable buffer/line driver IC. We'd probably just want two output devices in a half-bridge configuration. The output filter would be a regular LC filter. I'm not sure how big it would need to be, though. That will take some design work, but the inductor would probably need to be wound by the builder. There is also an issue with the power supply. Something like this really needs a split supply. A virtual ground may work, but I'd need to look into it. It would require a capacitively-coupled output, which may (I'm not sure about this) affect the circuit's performance.

The bottom line is that Class D is probably do-able, but may not be worth the effort. A universal PCB would need to be developed, and, even then, I'm not sure how much of a problem EMI would be. Part of the reason most of this stuff is implemented in surface mount is that EMI is a real problem, and I don't know how well a through-hole design would do on this front. I think moving the power source out of the guitar is a better and much more feasible idea. I'd like to give it a shot anyway, but for now Class D is at the bottom of my list behind getting a working sustainer installed and rebuilding the ebow.

Ben,

I've used CA debonder before. In my experience it works anywhere from ok to not at all, depending on the application. I may try it on a test coil sometime, but I'd like to stay away from it for my pickup/driver coil.

Link to post
Share on other sites

alright, I've started winding. Attempting to figure out if the coil's resistance measures out to 8 ohms has been a real pain in my ass though. :D I've been trying to use epoxy gel as I wind the wire around the driver, but that's been just making a mess and leaving me with a lot more to redo when I mess up. Could it make sense to immerse it all in wax (the driver) in much the same way you pot a pickup? Or is that a no-no?

Link to post
Share on other sites
I suspect that there is already plenty of clipping compression anyway with a hot preamp like mine into the LM386 and the resulting sustain is probably just as good.

The problem with clipping as compression is that as much as 20% or more of the energy generated is harmonic content that will not reinforce the fundamental, and may even interfere with it, so while the overall level is limited, the level of the fundamental (and hence the drive) may actually be reduced. Gain control should be noticably more efficient at driving the string, and limiting the preamp's frequency response with a steep low pass filter should eliminate almost all of the higher overtones, resulting in a reasonably clean driver signal, especially for the smaller strings, which are apparently more difficult to drive - somebody with a spectrum analyzer (and too much time on his hands) could probably figure out the necessary filtering in short order. Just my too sense... :D

Link to post
Share on other sites
Could it make sense to immerse it all in wax (the driver) in much the same way you pot a pickup? Or is that a no-no?
Well, Waxing is not easy to do and there is a risk of fire! The way I did it seemed to work each time without hassles with the PVA...simple, cheap and effective. Here is a complete sequence of photos again on my pickup driver combo, but the same applies for dedicated drivers...

The bobbin made up and ready to wind...

PD5.jpg

What you will need...glue, multimeter, wire, etc...

PD1a.jpg

Starting to wind...notice I have already soldered on one of the leads to the start of the coil...

PD2a.jpg

You can see the glue squeezing through the windings as I go...when you cant see the white glue anymore, it's time to add a little more... (notice the white sandpaper used to remove the enamel to take resistance readings on the coil)...

PD3a.jpg

I used cardboard to stiffen the flexible bobbin top...it wasn't stiff enough and you can see it tries to force up the ends where it's tighter...

PD4a.jpg

After winding I used spring clamps to hold the ends down while it set. Blue tape is tightly wound around it after the end lead is soldered on...

PD7a.jpg

The blue and green are the driver wires, red and white the pickup. The pickup coil is covered in black tape and a notch in the bobbin allows the driver wires to pass down to the exit hole. The top of the cover has been removed...

pup-driver1a.jpg

The end result turned out pretty neat...

pup-driver1b.jpg

So...I hope that helps

pete

I haven't been able to hook it up to a real coil yet, but my tests on the Ruby-Fetzer indicate that there is going to be a substantial amount of clipping.
Yes, and mine even more so...this clipping already provides compression itself...like a fuzz box. Maybe a simple fuzz box would make the perfect preamp...

I spent some time looking at Class D stuff the other day. I was hoping to find an integrated IC, similar in application to the 386.
Oh they are out there, but there are issues with them. What I liked about them is that the outputs don't seem to be connected to ground which may address some of those issues, and they have popless switching built in...some even an idle mode to send them to sleep! The downside is that they are SMD and way too small for had soldering (in the main), seem to have trouble putting out consistant power over extended periods and are far more expensive in small quantities (if you can get them) than the old LM386. It would still be interesting to try, but I think the remote power is an even better option. Another idea would be to use a stereo chip with a EMI cancelling dual coil design and having different output filters for each side to run the coils for the low and high strings... Sometime though...too many ideas!!

:D

The problem with clipping as compression is that as much as 20% or more of the energy generated is harmonic content that will not reinforce the fundamental, and may even interfere with it, so while the overall level is limited, the level of the fundamental (and hence the drive) may actually be reduced.
This reminds me of the early days of the tread..where you were suggesting that a square wave signal amy be best to drive it while I was convinced clean drive would provide a better polyphonic response. I don't know. Connecting a speaker in place of the driver provides for an overdriven sound, but I don't know what the effect of the static driver coil will have (cause you can't hear it!). I think the LM386 at x200 with a hot preamp is going to be distorted...another reason for remote power....more clean power and a range of amp options. I did try using stompbox compressors for preamps which worked well too. That LM386 compressor circuit sure is interesting though, very tempting for when I get my soldering iron back :D Edited by psw
Link to post
Share on other sites
This reminds me of the early days of the tread..where you were suggesting that a square wave signal may be best to drive it...
:D Did I say that? Actually, what I thought was that a square wave would be good enough, especially with a hex driver and bandpassed signals for each string. Now that we're down to a single channel, and having near universal problems driving the higher strings, I've developed a sneaking suspicion that optimizing the driver signal to drive the most difficult strings has become much more important. But that's just me -YMMV! :D
Link to post
Share on other sites

Ah yes...though I may have distorted you view somewhat! Anyway, I am a convert to what works for now. For sure there can be improvements but if the basic concept works, go with the flow for now... pete

Link to post
Share on other sites

I'we been following this post for as long as I remember, and decided yeasterday was the time to start building a sustainer.

I constructed the driver like this:

The bobins are cut out of black plastick. I taped six neodym magnets with a diameter of 1 cm each to the bobbin with double-sided tape. All magnets have the polarity on the same side. I the n taped the top-bobbin to the top of the magnets with the same type of tape.

I then winded the coil with 150 rounds of 30 AWG wire, resulting in a resistance of 6.4 OHM. The whole thing is potted with wood-glue.

Ended up with a tiny driver, wich suited well under the strings on my strat. I connected this to the output of my fetzer ruby, and it did nothing..... I could see the driver affecting the strings, but just in the same way as a single magnet without coil would.

Any ideas why it did'nt work? I am still a little unsure what the polarity of the magnets should be. I also suspect that the tape and bobbin on top of the coil places the actual coil to far from the strings.

I hope to get this thing up and running later today, so any tips and hints will be welcome.

magnet.jpg

The magnets used. Mine does not have holes in them, though.

sustainer.JPG

A quick drawing of my driver.

Edited by syndromet
Link to post
Share on other sites

Hi there syndromet, all the way from Norway! Nice to meet you :D

Ok...a few things come to mind. Those neodyminium magnets are too strong I am afraid...they are solid and 1cm in diameter, I'm not sure how thick but even at 3mm will be way too straong. They will be trying to pull down on the strings and stop vibration, may even be pulling them out of tune just being there. The sustainer will have to be working against the pull of the magnets.

So...that is the first thing that comes to mind. I can see why you used them though...6 of these exactly span the strings (6cm) but it is just too much. Maybe six ceramic magnets like this would be better. I used some Neodminium magnets underneath my 3mm steel cored driver and with others but they were very small...(3mm roundx2mm thick disks)...these I estimated to be as strong as my big ceramic magnet (or a typical pickup) but although it worked, was not as good as the bigger ceramic that spread the magnetism over the whole length, rather than in "spots" along the steel...here's a pic...

driverphoto2.jpg

The driver on the right is 3mm thick and has a thin cardboard bobbin and some tiny rare earth magnets stuck to the bottom of the steel blade in the core of the coil. The one on the left is made from a very cheap pickup with screws in the core to a base plate and a ceramic magnet on the bottom. The thin driver (right) was used as the model for my pickup driver but both worked well. Much better with the ceramic magnet though. The blade core worked better than the screw pole piece when bending strings as the sustain effect will get weaker as the string is bent away from the poles!

So...a new driver I am afraid. Other things you could try is to test the amp is working by replacing the driver with a speaker...turns it into a practice amp...an 8 ohm speaker from an old computer, radio or anything really should work for this. While you are at it, you can test a "power slide" trick. Use the back of the speaker magnet as a slide on the stirings, the vibrations of the speaker (not the electromagnetism) will cause the string to vibrate...a lot of fun!

Anyway...back to your driver. I don't think these magnets are suitable. Also, 30 AWG...is that 0.2mm? This wire guage I have found to be most suitable. You could have added more turns...the am runs most efficiently at 8 ohms I believe, but there are also resonant frequencies in the coil to consider. The pictured coils really are about 8 ohms, but I must have made a mistake on my pickup driver (that works well) as it is more like 7 ohms, much like yours. You will still get a response...so if you are getting nothing....something is wrong.

Another possible problem with your driver design is that the core is too wide. The core is 10mm wide...mine is 3mm. It would still work on the lower strings but at higher frequencies it would span both the up and down motion of the strings and be trying to push and pull them. Tim has a magnetic core of about 5mm I think that works well...but 10mm is a bit much I think.

OK...so I hope that helps...I am not sure that I understand all your questions but I will do a few short answers to see if that helps...

I could see the driver affecting the strings, but just in the same way as a single magnet without coil would.
I assume that you see the magnet attracting the string...that means it is too much...a pickup shouldn't pull at the strings enough to see!
I am still a little unsure what the polarity of the magnets should be.
Either way is ok...as long as they are all the same. If you reverse them (all the other way) it will create the harmonic effect just as reversing the wires to the driver does.
The bobins are cut out of black plastick. I taped six neodym magnets with a diameter of 1 cm each to the bobbin with double-sided tape.
This construction should be fine. Even if the magnets or core are not visible, if the plastic is thin, it will not have much of an effect. The driver does need to be close to the strings (I don't think you can do this as the strings would stick to it!) but only enough to freely vibrate when played on the highest frets. It also helps to cut back on EMI if the bridge pickup is close to the strings also.
Ended up with a tiny driver, wich suited well under the strings on my strat.
The strat is a great guitar for this project because they almost always have enough room between the neck and neck pickup. All my testing was done on a couple of cheap strats. To make it thin enough though you will probably need to put magnets inside the coil...or make it thicker with magnets under and cut into the scratch plate (only when you know it works though) or build it onto the pickup like I have done (but you may not want to do this to your pickup!).

Welcome again to the sustainer thread, and good work in just a day! pete :D

Link to post
Share on other sites

Just a few more quick questions from me! :D

1. Does anyone know a UK source for 7P3T or 8P3T rotary switches? (actually anything with 7+ Poles and 3+ Throws is good)

Or alternatively I have found THIS SITE, but its an american site.

2. I'm making my own pickups, and I am wondering which magnet configuration I should use for the neck pickup which will have the sustainer mounted on top of it.I have 2 alnico humbucker magnets to use.

What do you think would work best? stacking them down the centre of the pickup (1), or a P-90 style layout (2)

pickups3zr.jpg

I was originally going to go for #1, but reading what people have writen in this thread about EMI made me think #2 may be better.

( I may have completelty misinterpreted what I was reading, I dont know anything much about EMI except what I have tried to deduce from what other people have written here.... I was thinking that the opposing magnetic field at the edges the pickup would help prevent the driver interfering with the bridge pickup somehow... I think pete posted something like that about paperclips..?)

Thanks!

EDIT: it was staples:

"One used common staples to create a magnetised sheild up the sides of the driver with a polarity the reverse of the core. Theoretically this should have been great, but in practice, it seemed to make little difference...so I didn't mention it much."

But as you say pete; "in practice, it seemed to make little difference" .... maybe I'm worrying too much...

Edited by Ben
Link to post
Share on other sites
7P3T or 8P3T rotary switches

You can get stacking switches I know but these get very big and are unlikely suitable for a guitar. Otherwise, I personally don't think you will find such a device easily, and certainly not cheaply. I'm not even sure it is desirable in operation for the sustainer...but that is a personal opinion of course. Ideally I'ds like to see some push button operation or somthing as intuitive as a vibrato arm for adding in the sustainer at will. Fender's S1 switch also sounds promising and I am told is 4PDT which would be adequate and be identical in connections to the toggle switch I currently use.

Digital switching really is the answer but I don't know how to impliment such an arrangement. A digital switching circuit could be able to provide any number of switch opitions from a a single pole switch...even a momentary push button, or touch pad...or indeed any rotary switch, and that would really be the answer right there!

Anyway...as for the device...both magnet arrangements would work but with differences in pickup response and tone. There seems to be some confusion about what EMI is and the role of the permanent magnets...so I will try to explain.

A pickup senses disturbances in it's magnet field caused by the strings vibrating through it. These disturbances are "picked up" by the core or wire which produces a small current/signal which is amplified. A passive pickup requires thousands of turns of wire to produce a strong enough signal for the amplifier. The "shape" of the magnetic field influences the amount of the string is sensed and how strong the signal to an extent.

The driver acts in reverse...the string is held in the sway of a magnetic field created by the permanent magnets. An amplified signal in the driver coil, disturbs this field causing the string to vibrate at the frequency of itself, as this is the signal driving it...creating a feedback loop...and infinite sustain.

So...there are two types of magnets...the permanent magnet and the electro-magnet (the coil of wire with the amplified signal going through it). It is the electro-magnet alone that causes electro-magnetic interference (EMI) when the signal is picked up by the pickup.

More power then, will only result in more EMI. An inefficient coil will require more power for the same effect...more EMI. A design that is large and not focused...more EMI.

The permanent magnet wont stop it, but they and ferrous materials in the form of magnetic sheilding (staples, etc) may be used to influence it by creating some additional focus or soaking it up before it gets to the bridge pickup...but some will travel down the metal strings anyway, so simple distance between the driver and the operating pickup is best.

Please note that adding more magnetic power with permanent magnets will try and inhibit vibration, making it difficult for the string to vibrate freely (that's why you don't get super powerful magnet pickups) and so make it difficult to drive them too. The electro-magnet (the coil) is the key component of this device.

The thin driver design seems to be the most effective that I could devise that kept the EMI in an efficient compact form that keeps this energy localised around the driver. It has other advantages too....like the ability to combine the pickup and the driver, or to surface mount the driver...but these are secondary to the intent of the design.

Anyway....I hope that clears it up a little. A thin driver a distance away from the pickup, well potted to exclude any secondary signals produced within the coil by internal vibration with an average (pickup strength) magnetic field, driven by a circuit that is just powerful enough will produce the desired response.

As for switching....you may be on your own there...good luck, but you may have to review the rotary option for the sustainer control. However you switch it, get the thing working to a standard simple design before you or anyone else gets too fancy with it. If I had taken that advice initially, I could have saved myself a lot of effort and expense. Sometimes simple is best. I am sure there can be improvements made to it...I think people should have something to improve and understand why it works before launching into ideas that may prove to inhibit it's workings...perhaps to the point of it not working at all.

So...good luck everyone...and now it's back to my sleep and work cycle I seem to be on...cheers... pete

Link to post
Share on other sites

7P3T or 8P3T rotary switches

You can get stacking switches I know but these get very big and are unlikely suitable for a guitar. Otherwise, I personally don't think you will find such a device easily, and certainly not cheaply. I'm not even sure it is desirable in operation for the sustainer...but that is a personal opinion of course. Ideally I'ds like to see some push button operation or somthing as intuitive as a vibrato arm for adding in the sustainer at will. Fender's S1 switch also sounds promising and I am told is 4PDT which would be adequate and be identical in connections to the toggle switch I currently use.

Digital switching really is the answer but I don't know how to impliment such an arrangement. A digital switching circuit could be able to provide any number of switch opitions from a a single pole switch...even a momentary push button, or touch pad...or indeed any rotary switch, and that would really be the answer right there!

Anyway...as for the device...both magnet arrangements would work but with differences in pickup response and tone. There seems to be some confusion about what EMI is and the role of the permanent magnets...so I will try to explain.

A pickup senses disturbances in it's magnet field caused by the strings vibrating through it. These disturbances are "picked up" by the core or wire which produces a small current/signal which is amplified. A passive pickup requires thousands of turns of wire to produce a strong enough signal for the amplifier. The "shape" of the magnetic field influences the amount of the string is sensed and how strong the signal to an extent.

The driver acts in reverse...the string is held in the sway of a magnetic field created by the permanent magnets. An amplified signal in the driver coil, disturbs this field causing the string to vibrate at the frequency of itself, as this is the signal driving it...creating a feedback loop...and infinite sustain.

So...there are two types of magnets...the permanent magnet and the electro-magnet (the coil of wire with the amplified signal going through it). It is the electro-magnet alone that causes electro-magnetic interference (EMI) when the signal is picked up by the pickup.

More power then, will only result in more EMI. An inefficient coil will require more power for the same effect...more EMI. A design that is large and not focused...more EMI.

The permanent magnet wont stop it, but they and ferrous materials in the form of magnetic sheilding (staples, etc) may be used to influence it by creating some additional focus or soaking it up before it gets to the bridge pickup...but some will travel down the metal strings anyway, so simple distance between the driver and the operating pickup is best.

Please note that adding more magnetic power with permanent magnets will try and inhibit vibration, making it difficult for the string to vibrate freely (that's why you don't get super powerful magnet pickups) and so make it difficult to drive them too. The electro-magnet (the coil) is the key component of this device.

The thin driver design seems to be the most effective that I could devise that kept the EMI in an efficient compact form that keeps this energy localised around the driver. It has other advantages too....like the ability to combine the pickup and the driver, or to surface mount the driver...but these are secondary to the intent of the design.

Anyway....I hope that clears it up a little. A thin driver a distance away from the pickup, well potted to exclude any secondary signals produced within the coil by internal vibration with an average (pickup strength) magnetic field, driven by a circuit that is just powerful enough will produce the desired response.

As for switching....you may be on your own there...good luck, but you may have to review the rotary option for the sustainer control. However you switch it, get the thing working to a standard simple design before you or anyone else gets too fancy with it. If I had taken that advice initially, I could have saved myself a lot of effort and expense. Sometimes simple is best. I am sure there can be improvements made to it...I think people should have something to improve and understand why it works before launching into ideas that may prove to inhibit it's workings...perhaps to the point of it not working at all.

So...good luck everyone...and now it's back to my sleep and work cycle I seem to be on...cheers... pete

hey psw. how many poles would work for you, i know a little about electronic switching. :D but i am sure lk does as well. i have played with cd4016 for various projects.

hope that helps

Link to post
Share on other sites

Thanks Ansil...

On my guitar the on/off bypass switch requires a 4PDT switch and the harmonic function a DPDT switch...

I have looked into it but most switching things seem to require a circuit quite a bit bigger than the amplifier itself...a concern with on board stuff...however...the size of the switches themselves need to be taken into account, with digital switch system micro switch surface mount systems may be possible amoungst other options...

pete

Link to post
Share on other sites

Does electronic switching mean using relays?

Edit : 100th post! :D

Edited by Ben
Link to post
Share on other sites

Does electronic switching mean using relays?

Edit : 100th post! :D

Nope, it means CMOS.

My only issue with electronic switching is that, while it eliminates exotic (expensive) mechanical switches, it doesn't cut down on wiring clutter. It's also one more thing to build. On the other hand, it could be pretty small and could provide optimal switching. :shrug:

Link to post
Share on other sites

Why not relays? I have zero experience with them, but in principle they seem quite simple.

Link to post
Share on other sites

ahh.. touché :D

Edit: they're only tiny little things though, would it have any noticable effect?

Edited by Ben
Link to post
Share on other sites

I should think you'd get a 'pop' every time you switched setting..you probably wouldn't get a continous noise but it could be quite loud as the signal is very close to the electro magnet; and its not always the size of the magnet its how powerful it is. Another reason not to use relays is that they'd drain a 9V battery very quickly. They tend to use a lot of current compared to transistor type switching. I've played with the idea of transistorised switching before but its quite a lot of work when you could just have half a dozen toggle switches :D

:D sorry for hijacking your thread Pete!

Edited by Robert_the_damned
Link to post
Share on other sites

Dont know what your sorry for, I'm the one with all the stupid questions :D

Thanks for answering, and sorry to Pete for the deviation! :D

Link to post
Share on other sites

Does electronic switching mean using relays?

No...welcome deviation guys :D

Well, relay's could probably work, but you would need a few of them and away from the pickups. The principle is the same with digital, solid state switching but it is done with transistors on a chip. You will also need some kind of flipflop so that it would change when it senses a short current via a momentary switch.

This type of technology is how a computer works effectively....1000's of tiny switches! But, you need a 14 pin chip to get a DPDT switch so you would need three of these and a circuitboard to put them on...ekkk! With SMD this would be small enough...hmmm The wiring would be easier in some ways...wire everything in, then out...but still a lot of wires...and you still need some kind of switch. Boss Stompboxes have electronic switches and are so able to use a switch like that on the computer keyboard for instance.

There are other ways of complex electronic switching but I really don't know much about them. Common devices like calculators for instance obviously incorporate this type of thing in their circuitry. I had wondered if there wasn't some kind of integrated keyboard circuit that could be adapted...

For interest sake, here is a great little circuit for switching effects that uses a 4066 chip...Switching Circuit Page

Got to run again....keep on thinking... pete

Link to post
Share on other sites

The two major disadvantages of using relays are switching noise and current consumption - since this project already has issues in both areas, CMOS switching would seem to be a better solution (although it has its own problems). Keep in mind that switching a relay coil on and off will not only generate another magnetic field to be dealt with, but the inductive nature of the relay coil will probably induce switching noise in the power supply as well. I know of at least one homebrew Ebow project that used a relay coil as its driver. Just my two cents - YMMV.

And I wouldn't use a 4066 - a CD4053 gives you 3 SPDT switches on a single chip (see RG's ...Switching with the CD4053... article over at Geofex for more info).

Link to post
Share on other sites

All this talk about switching got me thinking about that eBow circuit again. I still have no idea how they do it, but my preliminary search didn't come up with any CMOS switches with a low enough on resistance to be useful for the driver phase switching. Here's what I came up with using a latching DPDT relay:

EDIT: Schematic removed because it doesn't work right. It was too complicated anyway.

Edited by fookgub
Link to post
Share on other sites
Guest
This topic is now closed to further replies.
×
×
  • Create New...