[sdiy] pitch to voltage

[harry]

Hi Toby (and Nick etc...)

I agree with Toby.  Waveshaping the actual signal is a much better way
to go.

You will need a separate pickup coil for each bass string. They are "hex pickup"
for guitar so maybe "Quad Pickup" for bass ???   Don't know a source.

Toby... If you can really make a suboctave (without any glitches, ever..) you
can do P/V conversion easily.  It is almost impossible to make a perfect octave
divider.

I have a design based on the Synclavier Guitar to Synth interface... it does not
EVER hop octaves... (it just shifts phase... sounds much better to the ear, but
still fucks up P/V converters)

Another P/V problem with guitar is that the low strings (besides being very long
in
period) are very massive (Bass is worse).  Even if you stop the strings very
quickly...
they will still ring for oh... 2 to 10 cycles. Enough for the P/V converter to
attenpt to
follow, and screw up the held note.

There are multiple S/H solutions, take the last "valid" data as the output. They
require you to accurately determine the start of any note (also tricky...)  Then
you select the
"n" sample if it is valid, or the "n-1" if not.

My best solution was to use a voltage controlled lag circuit on the P/V output.
This tracked the string amplitude... so it follows with small lag while the note
is fresh... and
increases the lag, essentially becoming a second S/H by the time the note is
almost
over.

Still. I'm not impressed with any of the methods out there. Most folk consider the
GR-300 design from Roland the best. This because it more or less uses sync from
the actual guitar signal to make sure the sawtooth is accurate.  Amplitude might
have a little error, but that is much less noticible than pitch error.

I'm using waveshaping these days and am quite happy. There is NO lag.

H^) harry

Toby wrote:

> on 11/3/01 10:47 PM,  at nick at dreamtheater.zzn.com wrote:
>
> > I am planning to create a semi-modular synthesizer for use with the electric
> > bass guitar.  I know that i will need an envelope follower, preamp, and
> > pitch to voltage converter.  I had no problem with the first two modules,
> > but the third has me stumped.  Could anyone point me towards some info on
> > pitch to voltagge conversion?  I'm looking for schematics and theory.
> >
> > Thanks,
> > Nick Liebrecht
> >
> Nick, you might want to screw the whole pitch-voltage conversion thing, I'm
> assuming that you want to take the voltage and use it in a vco(which can be
> nice because you can further vary the pitch(modulate it) in funky ways.)
> >From everything I've read on the list for the last two years, the
> pitch-voltage thing seems very painful to realize in a completely functional
> way.  I think it would be much easier just to do waveform conversion on the
> bass signal.  You can get a pretty nice square, triangle, sine coming out of
> your box, in addition, you can get a sub-octave and if you're crafty enough,
> get an octave up.  I actually got a PLL to do an 8x frequency multiplication
> then I divided that by nine and got a major second harmony on a square wave
> guitar signal.
>
> Anyway, I thought I might warn you, but maybe my warning will encourage you
> to find a great new solution to the pitch-voltage thing.  I just love it
> when somebody tells me something is difficult to achieve, because the first
> thing I want to do is figure out a way to do it.
>
> toby

--
Jihad Terrorism Conspiracy New World Order
Revolution Black Helicopters Freedom of
Speech First Amendment Rights: Carnivore Bait
go ahead and READ my e-mail I have nothing to
hide... how about YOU ???