[sdiy] Voltage references in VCO

[elmacaco]

Agreed,

But how to introduce it in a way that reproduces what people hear in the old
drifty moog oscillators?

I know the evolver has an oscillator slop parameter, and reducing the tuning
options on the a6 reportedly makes it sound better, but how exactly to dial
it in effectively is the question.


----- Original Message -----
From: "Ian Fritz" <ijfritz at earthlink.net>
To: "Rob" <rob at emulatorarchive.com>; "'Synth DIY List'"
<synth-diy at dropmix.xs4all.nl>
Sent: Thursday, April 13, 2006 7:53 PM
Subject: RE: [sdiy] Voltage references in VCO


> ARGHHH!!!!!
>
> As I have shown in great detail, residual drift can be zeroed out with
> appropriate active circuitry.  The "character" introduced by temperature
is
> not acceptable to me.  I have had several recording sessions ruined
because
> I didn't retune often enough.  If you want frequency variations, then add
> them electronically.  That way you can have whatever "character" you want.
>
>    Ian
>
> http://home.earthlink.net/~ijfritz/sy_cir9.htm
> http://home.earthlink.net/~ijfritz/sy_cir7.htm
>
>
>
> At 04:45 PM 4/13/06, Rob wrote:
> >Hi
> >Agreed, I'll add some more info! All the components need to be carefully
> >considered, with low drift OP177/LT1013 Op Amps, and 0.1% 15ppm resistors
in
> >the critical places. And yes temperature drift is still going to be an
issue
> >even when the voltage reference and line regulation has been sorted out.
If
> >you are building a new VCO you might as well make it high quality one...
> >
> >Regards
> >Rob
> >
> >No disagreement there, with careful notice of the big "IF". That is if
> >the stuff that gets these stable references really good enough to really
> >benefit from that. In a VCO that is peppered with TL084s the money for a
> ><1ppm reference is just thrown out money. For that a Tl431, LM336
> >(20-50ppm) is way better than the rest of the circuitry can handle.
> >
> >Besides nobody is going to toss their old synths because they did use a
> >LM7xxx style regulator... It was good enough for rock and roll back
> >then, so why not anymore?
> >
> >You might want to add a paragraph about choosing the right components to
> >make the most out of these references. The performance should match.
> >It is very easy to spoil the performance. Opamp drift exceeding that of
> >the reference for example.
> >
> >Don't forget that you can't use metal film resistors anymore, since
> >their 100ppm temperature coefficient even does exceed the precision of
> >your reference. Even with the 25ppm types.
> >
> >Cheers,
> >   René
>