[sdiy] monolithic VCO chips for FM??

[Scott Stites]

John Mahoney wrote:

"When Harry speaks, though, it's usually a good idea to listen."

100% agreed.  The talcum powder worked wonders!

----- Original Message -----
From: "john mahoney" <jmahoney at gate.net>
To: <synth-diy at dropmix.xs4all.nl>
Sent: Saturday, August 21, 2004 9:15 AM
Subject: Re: [sdiy] monolithic VCO chips for FM??


> > Well, the potentiometer per note approach would be a necessity if you
were
> to use
> > those VCOs that does not work in pitch so you can tune each note on all
> the other
> > octaves where double or 1 volt DC increment won't get you double the
> frequency.....
>
> Yes, that will work. When Harry speaks, though, it's usually a good idea
to
> listen. Harry said, "Temperature stability and no long term changes with
age
> and vibration would make the trimpots a tough choice. Calibration of such
a
> system could be a nightmare."
>
> Sure, you can tune the trimpots for each note. Without temperature
> stability, it's all pointless, though! Regardless, you will still be
locked
> into each of the pre-tuned pitches -- a tuning knob or octave up/down
switch
> will be impractical without accurate, expo VCOs. A vibrato CV (FM) will
have
> a different affect on each note (in some cases, this is okay or even
> desirable). Pitch bend will be *very* difficult to control, requiring a
> different input on each note to get the same degree of pitch bend.
>
> Since you are just starting in synth DIY, my [only slightly more
> experienced] advice is to follow the traditional path before blazing your
> own trail. There are many good reasons why you should use
> temperature-stable, exponential response VCOs. The ASM VCO is often cited
as
> an excellent, proven VCO design based on readily available parts (no
Curtis
> chips or other unobtainium). You can get ASM PC boards from (Mr.) Laurie
> Biddulph at http://www.elby-designs.com/.
> --
> john
>
> P.S. I hate that Oakley trademarked "unobtainium." Bastards!
>