Quasar Crackle/Pop in Treble Control (not dirty pot!)

[idy]

I have built the Quasar several times on Madbean pcb pattern, using RC values. Also have done the AC/RC on vero. On the PCB versions I had a strange crackle or pop on the treble control. BOth times. And even after swapping out pots several times. The one I have now has two loud "pops", both close to the counter-clockwise extreme. I have swapped the pots out (alpha, 50k linear) and the replacements do the exact same thing in the same place!

The earlier version got a nasty distortion on this same point in the pot travel, a sudden extreme fizziness that went away after I subbed the pots. The new circuit had the fizz on the first pot, just the pop on the second and third.

Any ideas? Whole baggy of pots with identical defect? I took one apart and there is no visible damage, no huge splash of solder or anything.

[madbean]

Hmmm...what IC are you using?

[idy]

Good question. Thank you!
I was using a mosfet, CA3260. When you asked I put in a 4558 and the problem went away. What was it?

[madbean]

Maybe the high input impedance of the the CA3260....? Dunno.

[idy]

So we still like the sound of the ca3260e better.
A little more on the pops: they only happen when volume is on maximum, at two points on the "cut" side of the treble control. I can also park the treble in the danger zone and get the pop by sweeping the volume back to full.

I have found out that the pedal only does this when it is plugged into another high impedance pedal: BYOC reverb,  Boss reverb/delay (even bypassed the buffer makes the popping happen)  FA-1 clone, a tremulous lune clone etc. My ampeg scrambler also pops with it, and it has a 1M input impedence.
The popping does not happen when the pedal goes into a fuzz face, or a rangemaster or a LPB or a simple MOSFET booster. (I thought that was high Z, maybe I added a too-small pull down resistor...)

Maybe next step is to breadboard a different kind of output buffer. I really like the OD with Baxandall tone control.