[sdiy] VCO reference voltages

[karl dalen]

Hmm lots of trolls today, have they escaped from Iceland recently? :)

--- Den fre 2010-04-16 skrev cheater cheater <cheater00 at gmail.com>:

> Från: cheater cheater <cheater00 at gmail.com>
> Ämne: Re: [sdiy] VCO reference voltages
> Till: "Ian Fritz" <ijfritz at comcast.net>
> Kopia: simon.oo.o at xs4all.nl, synth-diy at dropmix.xs4all.nl
> Datum: fredag 16 april 2010 23:51
> 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...
> 
> > 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?
> 
> > It is only when modules are added
> > that the rail voltages may change measurably, and only
> then when the PSU is
> > at or near its drive capacity.
> 
> You are here assuming a perfectly, or even properly,
> working
> PSU/synth. It might be a deadly mistake ;-) But then you
> can ask
> yourself how far do you want to go to correct the problems
> of someone
> connecting a toaster to the same voltage rails as your
> VCO.
> 
> Either way: at A5 this voltage difference on the exp input
> is a
> difference of frequency of over 1 Hz in comparison to an
> instrument
> which doesn't experience this. I'm just putting this into
> musical
> wording - I believe this is much better than many VCOs
> 
> Good (and important) point with the knob range though. I
> wonder if
> there is some tricky/smart way to use voltage references
> and still
> maintain full range. I'm thinking of using a range switch
> rather than
> knob, then you don't need a continuous transfer, that might
> make it
> simpler to implement a technique based on voltage
> references..
> 
> What range are you thinking of for your coarse tuning
> potentiometer?
> Full range? Or just, say, +/- 6 semitones?
> 
> If full range - are there many practical applications of
> such a huge
> range? I'm not saying there aren't, just wondering. The
> only thing for
> which I really use full range knobs on VCO frequency is
> adding a
> little audio-rate AM to the patch and changing the general
> setting
> from the LFO area to the audio-rate area while modulating
> the AM
> depth, for musical expression. This gives an effect similar
> to what
> happens when the player of a string instrument pulls up a
> string to
> change the speed of beat between his note and another
> instrument on
> the same note.
> 
> Another thing is when I'm using sync, but I don't use such
> big
> adjustments often. Sadly the coarse tuning knob is one
> mostly unused
> by me, because most of the time I touch it I end up with
> result that
> is way over the top. This got me quite interested, what
> other
> situations are there where you can make use of such big
> range for
> musical expression that will be nicely graded, rather
> tearing my ears
> out?
> 
> On Fri, Apr 16, 2010 at 19:21, Ian Fritz <ijfritz at comcast.net>
> wrote:
> > That's 800 ppm/K.  I try to get under 100 ppm/K drift
> with my VCOs. Of
> > course, I've just learned today that all my VCOs are
> crap, so what do I
> > know?
> 
> Who told you that? :^) I understand 'die meisten' means the
> same thing
> in German as 'the most' in English, but maybe your
> translator slipped
> up and wrote 'alle' in the subtitles ;-) clearly a case of
> 'lost in
> translation'..
> 
> Aaron,
> >> Most commercial *and* diy VCOs are crap.
> >
> > That is a rather strong statement.
> >
> > How would you quantify it?
> 
> I used quite a few :^)
> 
> Seriously - how many people active in this field do you
> think are
> truly masters of their art? Not all - so what's the
> percentage? Out of
> all VCOs that you can get out there, how many of them were
> made by
> those few select people? I would probably end up calling a
> guitar not
> made by someone who has mastered the basics of luthiery
> *crap*.. at
> most mediocre. If I made a guitar right now it would
> certainly be
> crap. The requirement of knowing what you're doing when
> making musical
> instruments should go for synths too, in my opinion, but
> unfortunately
> practical experience says it doesn't and people build and
> buy terrible
> little monsters anyway.
> 
> Bear in mind I wasn't voicing an opinion about the designs
> of anyone
> in this thread. I hadn't used your or Ian's VCOs, for one
> thing, and
> the fact that both of you contribute so much information
> here is good
> reason to believe you two's designs are, in fact, much
> better than
> 'crap' :) Either way no reason to feel hurt for anyone
> here.
> 
> Cheers,
> D.
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