18 and i dont know what i want .

[petey twofinger]

can i run this circuit at 18 volts ? lets say if i used 25 or 50 volt capacitor - i am hoping to use 18  v dc and have the circuit function well . curious about this .

the op amps are tl072 and lm358 - its similar to a dod 230 noise gate .

thanks !!

[ElectricDruid]

I'd say that yes, you can. The op-amps will certainly be fine, so there's no problem there. You're right to mention the cap voltages. Regard 25V as a minimum for an 18V supply, and 50V is better.

The only other query I'd have is the LED end of the vactrol/optoisolator. It's currently set up with a 10K resistor. At the higher voltage, that might well need increasing (since otherwise you'll double the current through the LED) but the correct value for that resistor is going to depend on what vactrol or LED/LDR you use, so it would probably need choosing for a specific build anyway.

[Mark Hammer]

Welcome back pete.  Long time, no see.

[duck_arse]

I'm not sure that led will ever turn on, with its Anode hard to ground and the opamp swinging around +9V [in case of 18V supply] at the Kathode. backwards, maybe?

actually, no, not +9V. I can't follow your bias setup. ok. I follow now.

[ElectricDruid]

I'm not sure that led will ever turn on
backwards, maybe?

Yeah, I thought so too.

[Wavelength]

Petey,

Hey it's Gordon, Rob Fetters buddy.6

If your building this for sure you could but I would suggest some changes. Any optical compressor I designed would have similar vdrop LED in the other direction to handle recovery better. Plus as stated above maybe that 10K is a bit much. In all the ones I have done that has been more like 1K.

I am not sure you really need 18V for this because of what it is doing but if you feel like it then going there is your choice. If it was me I would use an LTC1044 invert the 9V's and then run the damn opamps with a good +/- V regulated like +/- 6V or something like that and the circuit will sound better. Still not a fan of opamps but it's a compressor so the building blocks make it easy build.

Thanks,
Gordon