[sdiy] dx, chorus and Spock

John L Marshall john.l.marshall at gte.net
Fri Aug 16 01:44:36 CEST 2002


I suspect that you were observing an excellent performing VC filter. A less
than perfect sawtooth will have the first eight harmonics at decending

I'm guessing but I suspect that if the retrace is 1% of the total time then
the 100th harmonic would be missing. But, the amplitude would have been
1/100th of the fundamental anyway.

Take care,
Pacific Northwest DIY Synthesizer meeting, July 20, 2002
See: www.sound-photo.com

----- Original Message -----
From: "Gene Stopp" <gene at ixiacom.com>
To: <synth-diy at dropmix.xs4all.nl>
Sent: Thursday, August 15, 2002 4:23 PM
Subject: RE: [sdiy] dx, chorus and Spock

> Ooops sorry! Maybe you should listen to IQ also! Vast analog synthesizer
> noises. Very Genesis-like with the occasional gothic-metal. Start at their
> latest and work backwards. And once again of course a bunch of great guys,
> even if they don't make it across the pond very often.
> http://www.gep.co.uk/iq/
> This message intended for any die-hard progressive or neo-progressive
> (generally older farts like me who remember flowers, black light posters,
> kool-aid, and lava lamps).
> Uh oh better get back towards on-topic.... let's see, what DIYish thoughts
> have been travelling around in my head... oh yeah, here's one:
> Do precise waveforms sound better than "sloppy" ones? What do I mean by
> anyway? A few years back I worked for a company that was closing up their
> California division. We had a six months notice and I stuck it out to the
> end in order to collect severance pay. With lots of spare time and some
> expensive test equipment, I sat around and made synthesizer circuits. Yes
> those were the ASM-1 days. :)
> I remember building a 4-pole OTA VCF (Electronotes 4-pole 3080 design) and
> it sounded gorgeous.  As I ran a sawtooth into it and swept the cutoff
> resonance turned up a little, it was passing through each harmonic in the
> signal as though I had a big mixing board in front of me with all of the
> sinewave harmonics in order, and I was fading them in and out one by one
> sequence. Literally it was like 8th, 7th, 6th, 5th, 4th, 3rd, 2nd,
> fundamental all by themselves, clean, loud, and crystal clear. I was
> headphones at the time and I sat there doing this for hours (or so it
> seemed). I was mesmerized.
> I can't do that on any synthesizer, it seems. I've tried to get the same
> effect since, but no luck. Was it my signal source? I'll bet it was - I
> using a big HP3325 frequency synthesizer/function generator. The analog
> waveforms were good up to 11 Mhz, I seem to remember. So in the audio
> the waveforms were about as close to a math-class graph-paper function as
> you could get. The sawtooth slope was a perfectly straight line, and the
> reset trace was a perfect infinite slope (i.e. invisible on the scope). No
> jitter, no smearing, no rounding, no noise, nuthin. I think this made all
> the spikes on the spectral plot exactly where they theoretically should
> been, at exactly the right amplitude. I don't think that synthesizer
> oscillators have this kind of perfection and therefore their spectra are
> less than ideal ("smeared"?), so you never get that one-sinewave-at-a-time
> sound.
> Thoughts? Experiences? Anybody with an HP3325 or similar source of perfect
> waveforms wanna do some filtering tests? I do see them on ebay all the
> with a wide range of prices. Maybe I should lurk for an "as-is" 3325. But
> they're so bloody big.
> - Gene
> -----Original Message-----
> From: jhaible [mailto:jhaible at debitel.net]
> Sent: Thursday, August 15, 2002 3:27 PM
> To: Gene Stopp; synth-diy at dropmix.xs4all.nl
> Subject: Re: [sdiy] dx, chorus and Spock
> > Yes I know these guys!!! - I think my name is in the liner notes on one
> > more of their CD's. :)
> Great!
> Why did it take me so long to find this music ?! You should have told me!
> (;->)
> JH.

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