[sdiy] New here

[Harry Bissell Jr]

Hi Gene (inline)


--- Gene Stopp <gene at ixiacom.com> wrote:
> I can say that flute makes for a good source for a
> PV converter, at least
> the one I built some years back.
> 
> It's a 3080-based exponential VCO core (Electonotes
> workhorse VCO) with a
> home-built phase locked loop detector I made out of
> a quad NAND gate. The
> VCO tracks the mic signal, and the CV that's driving
> the VCO is brought out
> as the recovered pitch CV. My wife plays the flute,
> so one day I had her
> play into the converter and drove a Minimoog with
> it. It tracked perfectly
> and the response was plenty fast. The only thing
> that needed possible work
> was when the signal went away, the pitch CV dropped
> to minimum so the
> Minimoog pitch went sub-audio.
> 
> Question - what *should* a PV converter do when the
> input goes away? Should
> you latch the last stable CV with a sample and hold?

Yes... so that the decay portion of the synthesized
sound can still be used.

> If so, I found that you
> need to delay the CV by some amount (some kind of DC
> delay, like a cascaded
> S/H). 

Right again.  You can make it so the first trigger
selects the first S/H (no delay) and then later
samples
can be taken from a later tap in the S/H chain

Another way, if you can be sure that the signal fades
away slowly before the lock is lost... is to use
envelope following to set a variable LAG... as the
signal gets smaller, the lag time increases until it
becomes a total S/H of the last value. 

This method made the 360 Systems "Slavedriver" almost
work, imho.

You could use a footswitch and S/H (also a 360 Sys
option). pita imho

The sample command is triggered by the lack of
> input, and by that time
> the CV has already dropped.

Don't know how flute decays... guitar almost always
dies
over several cycles so its a big problem.

H^) harry


> 
> Or, let the CV drop, and turn off the gate when the
> input falls below some
> threshold, which is higher than the lost phase-lock
> point.
> 
> I was going to take the latter approach, since I did
> not want to add
> latency. I never did add the envelope follower to
> make the gate...
> someday...
> 
> Best Regards,
> 
> - Gene
> 
> 
> 
> -----Original Message-----
> From: Harry Bissell Jr
> [mailto:harrybissell at prodigy.net]
> Sent: Tuesday, January 27, 2004 11:08 AM
> To: Thomas Dunker; synth-diy at dropmix.xs4all.nl
> Subject: Re: [sdiy] New here
> 
> 
> Hi Thomas
> 
> for a good envelope follower design, see the Design
> Ideas submission for DEC 25, 2002 in EDN Magazine
> 
> "Envelope Follower combines fast response, lowest
> ripple" by Harry Bissell Jr (me)
> 
> I have some experience with P/V conversionn as well,
> but not for flute.  Most of my experiments have been
> with guitar, and I do not find it to be very
> satisfying.
> 
> My current work is using the actual waves produced
> by
> the strings as the sound source, warped, modified
> etc
> and fed to filters etc.
> 
> The PV-1 pitch to voltage converter was based on the
> Etherwave (theremin) P/V converter designed by Bob
> Moog
> and used with permission.  Many people have used it
> with
> theremins (which have a continuous wave, no pauses)
> as
> well as with analog keyboards to get a CV out.  I've
> played a little with guitar and microphone with it,
> and am not too pleased with the result (I'm fussy -
> the low-fi people might actually like it !).
> 
> The boards (from EFM) are sold out but probably if
> you
> asked on list, someone would prlly offer you a blank
> board for some price (they can't ALL have been built
> or I'd get MORE e-mail).  I can provide the
> documentation.
> 
> enjoy
> 
> H^) harry
> 
>