[sdiy] CEM / V3340 output spikes

Matthias Herrmann matthias.herrmann at fonik.de
Mon Aug 14 13:39:22 CEST 2017

the negative overshoot of the ramp is what i experienced with the original
CEM3340 as well. seems it is by design.


> -----Ursprüngliche Nachricht-----
> Von: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] Im Auftrag von
> Martin Klang
> Gesendet: Montag, 14. August 2017 13:00
> An: synth-diy at synth-diy.org
> Betreff: [sdiy] CEM / V3340 output spikes
> Hello list,
> I've been prototyping with the Coolaudio V3340, their CEM3340 clone.
> I'm seeing a voltage spike on the ramp output at the oscillator reset
> point. The output, which is 0-8V positive (with +/-12v supplies), swings
> negative as it resets.
> This is not so much an issue for a sawtooth waveform, since it just adds
> more harmonics (flavour!). My problem is that I'm cross-fading the ramp
> and tri outputs to get a variable output waveform, and the spike bleeds
> through in an ugly way.
> Is this something anyone else has come across, with the V3340 or the
> original?
> I've tried loading the output in different ways but it doesn't seem to
> make much of a difference. A fixed filter can get rid of the spike, but
> then I'd loose a lot of lovely high harmonics!
> any ideas would be much appreciated!
> cheers,
> Martin Klang
> Rebel Technology
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