Stereo hard panning repeat percussion design help

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Stereo hard panning repeat percussion design help

Postby Nocentelli » 29 Apr 2017, 09:39

I made a vox RP-like pedal which i really like using moosapotamus's skippy schematic for the 2N6027 PUT implementation and the hummingbird jfet audio stage. Whilst playing earlier this evening through a pair of amps, i was gripped by a powerful desire to make a circuit that could do the percussion-style "trem" thing but alternating rhythmically between stereo outs.

i have only a very vague idea of how this could be achieved (with an analog circuit - i imagine it would be relatively straightforward in dsp). I have done a stereo panning tremelo before, where the signal is rhythmically crossfaded between the outputs using a single LFO controlling the output of a pair of circuits, and the LFO output being inverted for the right channel. However, for a panning repeat percussion, i feel that the left output would need to be muted when the right passed that reverse sawtooth plosive thump, then immediately reverse, so right is silent whilst left emits the thump. Obviously this would need to be tightly sync'ed so the initial, sudden attack of each signal burst was not missed when the output signal swapped sides.

I have not seen any RP-soundalike circuits using different components that i could modify, and i get the impression the characteristic vrp sound is entirely due to the mechanism of the raw capacitor discharge shape controlling the output. SO my only idea to provide a panning RP would be to have the guitar signal split into two channels, and have the UJT/PUT based LFO signal trigger some kind of flip-flop arrangement, so each cycle of the LFO would swap which audio path was triggered AND apply that cap discharge to the appropriate channel...

...and that is as far as i have got. I have little idea of how the "inactive" channel could be muted, or whether the RP lfo could even be tapped for a sync signal to trigger the flip-flop panning/muting implementation. Any advice, suggestions or party-pooping will be gratefully received.
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Re: Stereo hard panning repeat percussion design help

Postby ~arph » 30 Apr 2017, 12:27

Ok, so you want the pulses to alternate between two channels right? I think something like this might work. I'd say the first thing you need to do is to is as you suggest create a signal that selects the output. Something like a comparator into a flipflop should do. The output voltage of the flipflop can be scaled so it is half the supply voltage when the output is high. If you use the output as a vref on an inverting opamp stage it will go on and off with flipflop. You need an inverted version of this control signal too. You can invert this after the flipflop or use a second comparator flipflop pair.
Also check the panning for fun article on geofex for ideas on panning. But you've probably already seen that as you did a planner before
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Nocentelli (30 Apr 2017, 14:03)
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