Author Topic: Pot Swap in Op Amp drive  (Read 1853 times)

spacecommandant

Pot Swap in Op Amp drive
« on: January 26, 2023, 03:43:08 PM »
If I were to pop an A500k pot into the Drive and I wanted to keep the amount of gain and frequency the same, is it as simple as lowering R4 to 1k65 and raising C2 to 220n to get the approximate corner frequency? I imagine C3 and R6 might need to be changed but I'm not sure how to factor these in.

FSFX

Re: Pot Swap in Op Amp drive
« Reply #1 on: January 26, 2023, 04:02:58 PM »
If I were to pop an A500k pot into the Drive and I wanted to keep the amount of gain and frequency the same, is it as simple as lowering R4 to 1k65 and raising C2 to 220n to get the approximate corner frequency? I imagine C3 and R6 might need to be changed but I'm not sure how to factor these in.

With a A500k pot rather than a A1M changing R4 and C2 to the values you say (1k65 and 220n) will keep the low end response pretty much the same as the original. To get the top end response similar then C3 needs to be doubled in size to 440p (470p will do fine). I would halve the value of R6 as well.
« Last Edit: January 26, 2023, 04:09:03 PM by FSFX »

ElectricDruid

Re: Pot Swap in Op Amp drive
« Reply #2 on: January 26, 2023, 07:27:30 PM »
+1 what FSFX said.

Half of 3K3 is 1K65, but 1K5 is close but a bit low. Twice 100n is 200n, but 220n is close but a bit high. Together 1K5/220n is pretty much spot on - both 1K5/220n and 3K3/100n are 482Hz, way within the tolerance of the components.
500K/1K5 gives slightly more gain that 1M/3K3, but not so much you'll care - there's only 1dB in it, which is not even close to an audible change in this situation.

The biggest change is turning 220p into 470p, since that goes up a few percent, and brings the maximum cutoff down a tiny bit. But again, not so much you'd really notice. 720Hz vs 680Hz, roughly.

So yeah, go for it. It's the same thing with different values.

spacecommandant

Re: Pot Swap in Op Amp drive
« Reply #3 on: January 26, 2023, 08:54:01 PM »
Great, thank you!