[sdiy] Fet to short pedal input?

[Roman Sowa]

Neither drain or source has to be "fixed". They can fly at whatever 
voltages both sides of glide pot is experiencing. You only need to make 
sure that gate voltage is a few voltages higher than any possible Source 
voltage to turn it on, and at least no higher than Source to turn it 
off. In simple terms, switch it between plus and minus power rails, r as 
in this case between +15 and 0V should be enough.
And to get rid of substrate diode that will spoil it in glide circuit, 
just connect 2 MOSFETs back to back. Or should I say source to source.
Common MOSFETs accept +/-20V Ugs

Roman

W dniu 2025-11-28 o 22:51, Pete Hartman via Synth-diy pisze:
> Am I just missing something here? If neither the Source nor the Drain is 
> tied to anything resembling a fixed voltage, then what does the Gate 
> have to "compare" to (yes I'm being imprecise about the mechanism of a FET).
> 
> When one side is a ground, certainly, that makes sense to use a FET for 
> muting or even a BJT for switching (I've done the same).  But FETs 
> floating in the air ... unless there's a DC offset in that signal going 
> to the portamento circuit that can be relied on, I don't see how that 
> would work.
> 
> On Fri, Nov 28, 2025 at 3:26 PM brianw <brianw at audiobanshee.com 
> <mailto:brianw at audiobanshee.com>> wrote:
> 
>     A relay will certainly have the conductive properties of the pedal
>     switch.
> 
>     My questions are 1) how fast will the relay open circuit after the
>     Frostwave converts MIDI velocity to voltage? and 2) how many notes
>     can you play before the relay wears out?
> 
>     If the relay doesn't 'release' quickly enough, then the portamento
>     won't work as expected, since the early part of the note will jump
>     instantly towards the new pitch CV. In other words, the timing
>     between the Note On gate (when the pitch CV changes) and the relay
>     disengaging has to be zero (or less!). One possible solution is to
>     delay the Gate - perhaps using the Frostwave as the gate source.
> 
>     Brian
> 
> 
>     On Nov 28, 2025, at 7:39 AM, Michael E Caloroso wrote:
>      > You really need a control element with infinite resistance (open
>     circuit).  That element needs to have open circuit and short circuit
>     states and it's hard to beat a relay controlled by a Darlington BJT.
> 
> 
>     ________________________________________________________
>     This is the Synth-diy mailing list
>     Submit email to: Synth-diy at synth-diy.org
>     <mailto:Synth-diy at synth-diy.org>
>     View archive at: https://synth-diy.org/pipermail/synth-diy/
>     <https://synth-diy.org/pipermail/synth-diy/>
>     Check your settings at:
>     https://synth-diy.org/mailman/listinfo/synth-diy
>     <https://synth-diy.org/mailman/listinfo/synth-diy>
>     Selling or trading? Use marketplace at synth-diy.org
>     <mailto:marketplace at synth-diy.org>
> 
> 
> ________________________________________________________
> This is the Synth-diy mailing list
> Submit email to: Synth-diy at synth-diy.org
> View archive at: https://synth-diy.org/pipermail/synth-diy/
> Check your settings at: https://synth-diy.org/mailman/listinfo/synth-diy
> Selling or trading? Use marketplace at synth-diy.org