This amplifier had a case of scratchy volume controls, so when you adjust the volume you get crackle from the speakers, and at full volume they actually because unreliable and the signal would drop out.
Being a power amp (a big one, 1500watts!) the volume knobs are usually left at max, and the level is controlled by the separate preamp. Having to keep the knobs slightly below max, and occasionally having the amp go crackly wasn’t ideal, so I decided the best option was to bypass the volume pots.
Inside the amp:
The original wiring for the volume pots:
and the modified wiring:
I just moved the output wire from the wiper terminal of the pot (middle) to the input terminal (left in the photo) so the signal passes straight through to the amp. No more crackle!