[sdiy] Tri-core phase reset to +5v or -5v

David G Dixon dixon at mail.ubc.ca
Sat Mar 9 09:32:13 CET 2019


The original Intellijel Rubicon had that feature.  There was a panel switch
for determining whether it reset to +5 or -5 volts.  It's very easy to do.
You simply follow the integrator with a unity gain inverter with -5V also
summed in at unity gain to shift the integrator output by +5V.  Send this
inverted and level shifted output through another inverter then into the
comparator.  Switching between the outputs of the two inverters selects
between reset voltages.

> -----Original Message-----
> From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] On 
> Behalf Of Rutger Vlek
> Sent: Friday, March 08, 2019 11:44 PM
> To: SYNTH DIY
> Subject: [sdiy] Tri-core phase reset to +5v or -5v
> 
> Dear list,
> 
> I'm working on a triangle and square wave LFO, based around 
> an integrator and window-comparator and would like to reset 
> the phase of the triangle (and derived waveforms) with a 
> trigger event. I've simulated (Spice) to w common technique 
> to short out the integrator capacitor with a JFET, but that 
> of course only resets to 0V, while my triangle is moving 
> between +5V and -5V. Ideally, I'd like to choose which of 
> these voltages to reset to. Any tips on how to implement 
> something like that? It's important for me to maintain stable 
> temperature/tuning of the LFO frequency as I will use it to 
> modulate things at audio rate as well, and prefer to keep a 
> stable timbre as the result.
> 
> Regards,
> 
> Rutger
> 
> 
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