Buzz in speakers following POTS change

Hi all. I recently had to change the POTS in my Musical Fidelity A5 integrated as the old one only rotated a 1/4 turn. The new POTS is an exact latter day version of the original POTS. At listening distance, there is a noticeable hum from the speakers since the POTS was replaced. The hum doesn’t increase/decrease with volume.

The transformer also used to hum a little but only noticeable at very close distance. The transformer noise is now audible from listening distance. I have changed power cords, speaker cables, disconnected the only source, and the buzz persists. Nothing else in the environment has changed or further afield in the house.

Has anyone any suggestions before I buy ferrite beads for the power cables?



It sounds like a ground loop, but odd it showed up only after a component was replaced.

Have you tried a cheater plug which lifts the ground to the unit?

Have you tried unplugging everything from the integrated leaving only the power and the speakers connected and checked if the hum remains? If it goes away you have a classic ground loop.

Thanks Elk. It’s only the AMP as nothin else connected. I’m thinking it might be a bad/loose solder in the POTS when it was replaced.

Issue was definitely not there before the POTS was replaced. It’s there even when plugged into a power bar that has a passive filter installed.

I agree, it appears something is wrong with the repair.

Do you have pictures of the old (broken) and the new pots…? Or numbers…?

Hi Ronald. Both are Motorised ALPS 50KAX2. The initial 4 digits don’t matter (I believe) just the fact that it’s stereo and 50 ohm.

The new part code is RK27112MC01P.

I’m going to deoxit shortly to see if that cleans things up a little. I’ll make sure the transformer is seated tightly as well.

I seem to have found the problem. The tech didnt mount the POTS to the PCB properly and also left a lump of electrical tape on the PCB under the POT. Buzz barely audible now but will still bring back.

Thanks everyone for your input.

Excellent news.

Thanks for letting us know.

Even managed to get rid of the transformer hum by centering and bolting it down tighter.

A good result all round!