[sdiy] Deep thoughts on Old drum machines: the "VCA"

Roman Sowa modular at go2.pl
Sun Jan 23 21:09:41 CET 2022

If you talk about Korg 700, the octave selector is not tuning the VCO to 
different octave, but uses waveshaping (basically adding divided square 
to the saw) to create sawtooth exactly one octave lower. This is not 
perfect, so you can see the glitches in the middle of the ramp. And 3 
glitches in lower octave and so on.
This way they had no problem keeping octave switch always in tune and 
VCO didn't have to track in wide range.


W dniu 2022-01-22 o 22:51, Adam Inglis (synthDIY) pisze:
>> On 27 Nov 2021, at 05:16, Mattias Rickardsson <mr at analogue.org 
>> <mailto:mr at analogue.org>> wrote:
>> Probably also for synth sounds. Among all potential cases of people 
>> saying that "the old synth sounds better than the new 
>> version/clone/emulation/whatever", offset thumps might be one of the 
>> unknown secrets that reverse engineers often miss.
> I’ve wondered something similar.
> When I’m editing recordings at the waveform level in Cubase, I’ve 
> noticed that my most, er… ‘characterful' synths have the most waveform 
> distortion about the zero axis (sorry, can’t think of the technical 
> term!) i.e. the waveform will be skewed more above or below the line 
> (Korg 700, TB-303, SH-2000) whereas more polite sounding synths are 
> perfectly symmetrical about this axis. I’m assuming there is some kind 
> of DC offset going on there, but that may not be the correct explanation
> A
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