[sdiy] VCO reference voltages

[cheater cheater]

On Sat, Apr 17, 2010 at 01:08, David G. Dixon <dixon at interchange.ubc.ca> wrote:
>> David,
>> > PSU load is largely fixed
>> > unless modules are added or removed from the cabinet
>>
>> But what about transient loads that other modules can create? Say,
>> other VCOs which are not nicely decoupled...
>
> If modules are changing the rail voltages, I'd say one has bigger problems
> than drifty VCOs!  But, then again, maybe I'm smokin' crack.  I only have my
> own system to judge by.

You'll find this is common..

>> > the rail voltages should remain fixed to
>> > within 1 or 2 mV during actual operation.
>>
>> Out of curiosity (pedantry?), where are you getting this figure from?
>
> Just my own experience.  Every time I've ever measured my rails, they've
> always been within 1 mV of the last time I measured them.

Yes, but I think you might be one of the few people who understand
it's quite useful to have a good PSU :-)

> There is actually no good justification for not regulating the rails out to
> the panel pots,

Hm. What does 'regulating the rails out to panel pots' mean?

> unless a) you just don't care that much about these small
> fluctuations, or b) you do care a lot about saving a buck or two on extra
> parts or extra layout hassle.  In any case, regulating the tuning pots is
> very easy to do, and removes one more source of drift and uncertainty.

you're killing its soul!
;-)

It would be very interesting to make research with say 20 very similar
VCOs running in parallel, starting out with the most perfect one each
one would be a 'step down' from the previous one in regulation,
compensation, decoupling, parts matching, etc.. I'll have to do this
one day when I'm really bored :-)

>> What range are you thinking of for your coarse tuning potentiometer?
>> Full range? Or just, say, +/- 6 semitones?
>
> Mine are always full range.
>
> It's just what I started out doing, and I've seen no reason to change it.

Gotcha. Inertia is as good a reason to do things as any :-)

>> Seriously - how many people active in this field do you think are
>> truly masters of their art?
>
> Well, having just read some very interesting interviews and book chapters
> about Moog, Buchla and Oberheim, I found it quite reassuring that these guys
> basically had no clue what they were doing when they started.  We all learn
> by doing, trying, failing, succeeding, failing, two steps forward, one step
> back.  Some of us learn faster than others, and some of us persist in
> spectacular stupidity longer than we have any right to, but still, we're all
> works in progress.  Can any of us really lay claim to being "master of his
> art"?
>
> In my experience, greater master is almost always accompanied by greater
> humility.

Good thing I'm not a master then. I'll never have to be humble ;^>

Cheers,
D.