[sdiy] "Living VCOs" PCB in 2009 ?

Thu Dec 11 01:20:02 CET 2008

If you were to open the .wav file I posted, in a wave editing program,
you see some of that amplitude jitter on the Moog waveform but not the
digital waveform.  That's because when sampling a waveform, on one
wave cycle the sample might be right on the point of the waveform, on
another cycle samples may hit on either side of it, so you'll see less
of a point.  If anything, sampling adds randomness.  But when viewing
an animated fourier display, analog waveforms are very sterile and
stable.  Compare that to an acoustic instrument where the upper
harmonics are a noisy mess.

And the thing is that there isn't anything special about the Moog
waveforms that put them beyond other VCO's either in their sound or
any of their characteristics.  That was the point of my tests. People
would say the Moog sawtooth sounds so fat, or organic, or warm, or
some other superlative compared to the VCO's, but that's not the case.
 That's just fantasy.  This has nothing to do with how the Moog VCO's
track.  That's an entirely different issue.

And to address JH's description of the TGS and AH wars.  The reason
there was fighting there was because people were speculating about why
Moog waveforms sounded the way they did without actually comparing
them to others to see if they really did sound different or not, nor
actually looking at and measuring whether what they claimed was there
really existed.  I'm into reality, not fantasy.  But other's are into
fantasy, and when somebody puts hard reality in front of them that
they can't argue against, then it's the usual "shoot the messenger"
behavior so prevalent on these lists.  Some people don't like their
theories being proven wrong in front of other people, so they blow up
and start name calling.

And in regards to tuning, it's possible on an analog VCO to have it
tuned such that it's a little stretched or compressed.  My MOTM is
slightly off and I need to re-tune the thing.  With a number of my
sounds, I patch in a key triggered random sampled noise to offset the
pitch of the note so it behaves like a fretless instrument.  That will
add life to sounds that a typical analog VCO won't give you.  For
instance, a brass patch may sound organ like, but with the above
technique it suddenly sounds loose and chorusy.  That's the advantage
of doing things yourself, because you can do it to the point where it
is easily audible.

On Wed, Dec 10, 2008 at 5:40 AM, nicolas <nicolas3141 at yahoo.com.au> wrote:
> I think you may have struck on something.  Maybe the VCOs that people love so much are not jittery or unstable in their fundamental frequency (unless deliberately fed noisy CV).  But are somehow unstable in their waveshape.  That is to say unstable in their higher harmonic content.
>
> Maybe another avenue for someone to analyse who has access to some dry wave files and time on their hands.
>
> I know that my personal triangle to saw waveshaper puts out a sawtooth that wobbles around on the scope quite a bit even when the triangle going into it is nice and solid looking.  Its the pointy bits of the saw that are the wobbliest and they wouldn't affect your 65Hz jitter analysis.  My ears aren't quite discerning enough to reliably pick the difference though.
>
> Cheers,
> Nicolas
>
>
> --- On Wed, 10/12/08, Ken Elhardt <ken.elhardt at gmail.com> wrote:
>
>> From: Ken Elhardt <ken.elhardt at gmail.com>
>> Subject: Re: [sdiy] "Living VCOs" PCB in 2009 ?
>> To: "Antti Huovilainen" <ajhuovil at cc.hut.fi>
>> Cc: synth-diy at dropmix.xs4all.nl
>> Received: Wednesday, 10 December, 2008, 7:53 PM
>> This was several years ago and spanned the The-Gas-Station
>> and
>> Analogue Heaven lists.  It started out with people claiming
>> the Moog
>> VCO was real magical and nothing else on earth sounded
>> anything like
>> it.  You know, the usual B.S. that fills these lists.
>> After getting
>> actual Moog wav files from a couple of different people it
>> turned out
>> there was nothing special about it at all.  It's
>> waveforms looked and
>> sounded like others, it had LESS jitter than other
>> oscillators, and
>> drift could be easily programmed, and all kinds of other
>> VCO's were
>> tested and compared too and files were put online to put to
>> rest some
>> of the ridiculous things people said about them.  I posted
>> cycle to
>> cycle jitter measurements too.  Most of those files are no
>> longer
>> online except the very last one I posted which compared
>> that supposed
>> super magical Moog 901 VCO with a miserable digital
>> waveform generated
>> in Cool Edit Pro and there is virtually no audible
>> difference.  The
>> wav file below alternates between the Moog and a digital
>> waveform a
>> few times over the length of the file.  Jitter measurements
>> comparing
>> the Moog and a modern Technosaurus VCO are after my text
>> and it can be
>> seen that the Moog has about 3 times less.
>>
>> http://home.att.net/~elhardt2/Sawtooths.wav
>>
>> Now if somebody is designing a new unstable VCO, that's
>> fine, if
>> that's what is meant by "living".  If I want
>> unstable, I use my
>> Doepfers.  But nobody should be claiming that the Moog VCO
>> is somehow
>> different/better than other VCO's.  There just
>> isn't anything there to
>> back that up.
>>
>> One of the many hypothetical potential products that
>> I'd like to come
>> out with is called the Acoustic Oscillator and produces
>> "alive" and
>> constantly changing waveforms the same way acoustic
>> instruments do.
>> Prototyping the thing up in Reaktor has been on my list for
>> a couple
>> of years now.
>>
>> ------
>> Moog Modular 901 VCO 65Hz, 40 cycles measured.
>> Cycle to cycle jitter in microseconds.
>>
>> +1.4  -0.7  -0.7  0.0  +2.1  -0.7  -0.7  0.0
>> +0.7  +0.7  0.0  +2.8  -2.1  -0.7  +1.4  0.0
>> 0.0  0.0  0.0  -0.7  0.0  +0.7  -0.7  +0.7
>> 0.0  -1.4  +1.4  +7.0  -1.4  0.0  0.0  -1.4
>> +0.7  0.0  +0.7  0.0  0.0  0.0  -0.7
>>
>>
>> Technosaurus Selector VCO 65Hz, 20 cycles measured.
>> Cycle to cycle jitter in microseconds.
>>
>> -2.1  +3.5  -4.9  +3.5  -2.1  -3.5  +2.1  +0.7
>> 0.0  +1.4  -2.1  -2.1  +3.5  +2.8  -6.3  +4.2
>> +1.4  -2.1  -2.1
>> ------
>>
>> On Tue, Dec 9, 2008 at 8:41 AM, Antti Huovilainen
>> <ajhuovil at cc.hut.fi> wrote:
>> > On Tue, 9 Dec 2008, Ian Fritz wrote:
>> >
>> >> Ken did a superb, thorough study of this.
>> It's really depressing that
>> >> nobody seems to believe his results.
>> >
>> > I seem to have missed this. Can someone post a url to
>> the results? (Which of
>> > course include detailed explanations of the tests,
>> right? (*))
>> >
>> > Antti
>> >
>> > "No boom today. Boom tomorrow. There's always
>> a boom tomorrow"
>> >  -- Lt. Cmdr. Ivanova
>> >
>> > *: Any study which only says "Here are the
>> results, but we're not telling
>> > you exactly how we got them" is largely useless.
>> >
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