Ok, what I'm trying to do is make a sustainer for a guitar (this uses magnetism to keep the string vibrating indefinetly)
I've spec'ed the driver coil & built it.
I created a simple little circuit (preamp & small power amp IC) & squirted a sine wave into (at all the six strings frequencies in turn) & achieved good sustain with all strings.
Excellent...or so I thought!
So I then replaced the sig gen with the guitar's bridge pickup output signalas the 'source signal' ...in this scenario I can only get good sustain on the three lowest (thickest) strings.
now this flies in the face of logic - when using a sig gen you have to get the frequency 'bang on' (tricky) to achieve string resonance/sustain, but using the guitar string itself removes this issue.
I'm thinking here this must be a phase issue. When using the sig gen, there is no danger of the source signal - ie the output of the sig gen - being affected by the sustainer driving the string & cancelling the source signal. But when you use the the sustainer with the guitar string & source pickup, then there's a very real possibility that phase differences can cause havoc with the sustaining.
So to my question ....say for a given frequency of 330Hz (top E String)...how can I construct a circuit where the phase can be altered tweaked to see if I can coax sustain (ie to prove that it is indeed phase that's the problem)problem?
I've spec'ed the driver coil & built it.
I created a simple little circuit (preamp & small power amp IC) & squirted a sine wave into (at all the six strings frequencies in turn) & achieved good sustain with all strings.
Excellent...or so I thought!
So I then replaced the sig gen with the guitar's bridge pickup output signalas the 'source signal' ...in this scenario I can only get good sustain on the three lowest (thickest) strings.
now this flies in the face of logic - when using a sig gen you have to get the frequency 'bang on' (tricky) to achieve string resonance/sustain, but using the guitar string itself removes this issue.
I'm thinking here this must be a phase issue. When using the sig gen, there is no danger of the source signal - ie the output of the sig gen - being affected by the sustainer driving the string & cancelling the source signal. But when you use the the sustainer with the guitar string & source pickup, then there's a very real possibility that phase differences can cause havoc with the sustaining.
So to my question ....say for a given frequency of 330Hz (top E String)...how can I construct a circuit where the phase can be altered tweaked to see if I can coax sustain (ie to prove that it is indeed phase that's the problem)problem?
What happens if you increase an amplification factor, and power of your exciter?
In case of wrong phase the string should resonate, but resonate on harmonics. If it does not resonate that means feedback is too low.
But speaking of sustainers, I used ordinary compressors, with good practical results.
In case of wrong phase the string should resonate, but resonate on harmonics. If it does not resonate that means feedback is too low.
But speaking of sustainers, I used ordinary compressors, with good practical results.
Isnt that like using your amp to feedback the signal? (the way people have been extending sustain for forty years)
How about this:
http://en.wikipedia.org/wiki/All-pass_filter
Choose R and C for your corner freq (330Hz). Use a pot for R so you can tune it.
Murray
http://en.wikipedia.org/wiki/All-pass_filter
Choose R and C for your corner freq (330Hz). Use a pot for R so you can tune it.
Murray
Yes & no. The method you speak of uses acoustic feedback...& it's somewhat erratic to get right (it helps if you have a Marshall Stack turned up to '11' - not exactly what most people living in an apartment can do!)
Waveborn...the problem with cranking the power levels up...it that EMI spews out & into the source (bridge) pickup ....this gives a result akin to a microphone getting to close to the PA (positive feedback squeal)...so cranking the power up isn't an option.
I still think it's a phase issue - why else would the string resonate fine with a sig gen as the source....but when the bridge pickup is used and at similar drive levels to the sig gen - the strings don't sustain. I believe that phase discrepancies is cancelling some of the energy as fed into the string.
I once saw a man in Walnut Creek, on a farmers' market, who played the instrument he invented. It was like an upright guitar with more strings. It seems to me it was exactly what you are trying to achieve.
i have no wish to achieve playing an upright guitar with more strings at a farmers market.
First, increase the hight of the sustainer pickup, it should be very close to the strings and this should be no problem unless you're using a floyd rose. Possibly you can need to have it closer to higher strings (EBG) than lower (DAE).
I agree that if the system doesn't resonate at a basic harmonic it should do at 2nd or 3rd, but phase shifting can be interesting here anyway.
A one op-amp phase shifter is the circuit you may need here.
BTW are you using single coil or humbucking pickup for that purpose?
I agree that if the system doesn't resonate at a basic harmonic it should do at 2nd or 3rd, but phase shifting can be interesting here anyway.
A one op-amp phase shifter is the circuit you may need here.
BTW are you using single coil or humbucking pickup for that purpose?
I realise about the sustainer height being critical (this is in testing phase - the sustainer has adjustable height pole pieces but also because it's not permanently in place, I can freely move it up/down height wise) I have the pickup located as close as psscible to the strings *but* just far enough away to avoid the strings hitting the sustainer at the higher fret positions. - so spacing isn't the issue (Like I say - heaps of resonance when feeding the sustainer a sine wave from a sig gen
What pickup am I using?
I'm using a cheap catalogue stat copy with a single coil brifge pickup as the source, for no other reason than if I can crack it with that ...then the all other guitars should be a breeze! (I believe Sustainiac or Fernandes say that theie sustainers can only be used with other humbucking pickps? Having dablled with these for a while now, I can relate to that!)
What pickup am I using?
I'm using a cheap catalogue stat copy with a single coil brifge pickup as the source, for no other reason than if I can crack it with that ...then the all other guitars should be a breeze! (I believe Sustainiac or Fernandes say that theie sustainers can only be used with other humbucking pickps? Having dablled with these for a while now, I can relate to that!)
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This may give you some help:
http://projectguitar.ibforums.com/index.php?showtopic=16984&st=90
Search for sustainer on that site & there are lots of threads about building & troubleshooting. The main thread has been closed, but there are still lots of others.
http://projectguitar.ibforums.com/index.php?showtopic=16984&st=90
Search for sustainer on that site & there are lots of threads about building & troubleshooting. The main thread has been closed, but there are still lots of others.
Ok, I've now moved the guitar off the bench so to speak & onto my lap to play properly.
Firstly, I've had decent sustain across all strings on the bench...but under this scenario I'm flipping magnets around, adjusting drive (significantly), reversing driver feed wires etc.
Now, having played my guitar with the sustainer mounted, I'm fairly convinced that this is a phase issue (as opposed to a driver coil being wrongly spec'ed or the supporting circuit not delivering enough drive).
Why?
A couple of reasons. For example, if I twang an open E (330Hz), it doesn't sustain that well....yet if I detune the same string lower to say the B string (247Hz) - it then sustains fine....therefore same string, same driver, same open string...which kind of proves the circuit & the sustainer driver coil are fine. Now I'm pretty convinced isn't an impedance issue...as the difference in impedance between open E frequency & open B isn't that great (obviously reducing the frequency decreases the AC resistance & therefore allows more drive through the coil)...but the real 'deal sealer is' if I flick the harmonic switch (which reverses the wires to the sustainer coil ...essentially a 180 deg phase shift & fret the top E at the 12th fret, it's doesn't play the harmonic note (which is what should happen) ...it actually plays the fundamental note, which rings out as clear as a bell.
Same if I fret the same note but on the G string (ie playing the same frequency note as the E string at the 12th) - it rings out the fundamental clear as a bell - move anywhere else on the guitar fretboard (whilst in harmonic mode) & you can hear harmonics being coaxed into the string. Now bearing in mind all the 'harmonic mode' does is switch the phase of the signal to the sustainer coil by180 degrees...this more or less proves the issue of weaker sustain on top E is phase related.
But what is the solution...some form of phase control for 330Hz? (top E string frequency)
If you want to see what this is all about, I made a short clip where you can see the guitar being sustained.....
http://www.youtube.com/watch?v=DXitvBFwgKY
Firstly, I've had decent sustain across all strings on the bench...but under this scenario I'm flipping magnets around, adjusting drive (significantly), reversing driver feed wires etc.
Now, having played my guitar with the sustainer mounted, I'm fairly convinced that this is a phase issue (as opposed to a driver coil being wrongly spec'ed or the supporting circuit not delivering enough drive).
Why?
A couple of reasons. For example, if I twang an open E (330Hz), it doesn't sustain that well....yet if I detune the same string lower to say the B string (247Hz) - it then sustains fine....therefore same string, same driver, same open string...which kind of proves the circuit & the sustainer driver coil are fine. Now I'm pretty convinced isn't an impedance issue...as the difference in impedance between open E frequency & open B isn't that great (obviously reducing the frequency decreases the AC resistance & therefore allows more drive through the coil)...but the real 'deal sealer is' if I flick the harmonic switch (which reverses the wires to the sustainer coil ...essentially a 180 deg phase shift & fret the top E at the 12th fret, it's doesn't play the harmonic note (which is what should happen) ...it actually plays the fundamental note, which rings out as clear as a bell.
Same if I fret the same note but on the G string (ie playing the same frequency note as the E string at the 12th) - it rings out the fundamental clear as a bell - move anywhere else on the guitar fretboard (whilst in harmonic mode) & you can hear harmonics being coaxed into the string. Now bearing in mind all the 'harmonic mode' does is switch the phase of the signal to the sustainer coil by180 degrees...this more or less proves the issue of weaker sustain on top E is phase related.
But what is the solution...some form of phase control for 330Hz? (top E string frequency)
If you want to see what this is all about, I made a short clip where you can see the guitar being sustained.....
http://www.youtube.com/watch?v=DXitvBFwgKY
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You can still experiment with one opamp phase shifter circuit and even make it adjustable.
Also keep in mind, that physical placemnt matters a lot as well, your neck pickup is exactly at 1/4 of the total open string lenght (where 24th fret on superstrats is). Using two pickups or a neck humbucker may give different results.
Also keep in mind, that physical placemnt matters a lot as well, your neck pickup is exactly at 1/4 of the total open string lenght (where 24th fret on superstrats is). Using two pickups or a neck humbucker may give different results.
I guess the trouble I'm having, is how to choose the components (& select the centre frequency) for a one opamp phase shifter....to get close to the phase shift results I think I'll likely need (for example the top E string fretted at the 12th fret (circa 660HZ) ...it seems almost 180 degrees of phase shift is going to be necessary (on account when I reverse the sustainer coil feed wires, this note sustains well - & at the fundamental frequency). But then it begs the question...how will adding a phase shift impact the sustains that are sustaining well presently?!! I'll probably need to compromise & tune it for the least worst situation!
I've found a reasonable site (albeit in japanese english)....
http://www.aleph.co.jp/~takeda/radio/phaser/indexE.html
...where he shows a suitable circuit & goes on to give the formula for the 'center frequency' which will yield 90 degrees lag at that fequency. Therefore choosing 330Hz, as the centre frequency (the frequencies that seem to sustain poorly start in or around that frequency). I suppose I could use a pot to vary the 'centre frequency', which if I'm reading the explanation correctly will affect the phase change of frequencies close by (he reports that frequencies immediately above the centre frequency will have more lag)...time for a breadboard session methinks.
By the way...I'm now using a humbucker as the source -the single coil pickup I was using just had way too little output. (meaning I had to apply a lot of first stage gain to compensate...but this isn't good when you have a lot of EMI spewing all over the place with a single coil meaning no hum cancelling!)
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