Source of Buzz / Amplifier Repair

[virnuls]

My system has developed a noticeable buzz (rather than a hum) that it didn't used to have. I haven't changed equipment or cabling - it just appeared one day and seems to have got worse.

Before I look into repairs, I thought I'd canvas thoughts on possible causes other than the need for a repair. The buzz...

- gets quieter as the system warms up
- is on both channels for all sources
- disappears when the preamplifier is muted
- isn't volume-independent, but gets less loud than you'd expect as you turn up the volume
- is still there when all inputs are unplugged from the pre-amplifier
- isn't affected by the ground-lift switch on the back of the pre-amplifier
- is still there with a different mains cable into a different socket
- doesn't change if I switch from a balanced to a non-balanced connection to the power amplifier
- is slightly louder when the balance control is by-passed (strangely!)

I'm thinking therefore that it's a fault in the pre-amplifier (a Plinius M8). Could it be anything else?

Assuming that it is a fault, any recommendations for repairers? Thanks!

 

[Strider]

The more experienced among us might suggest a capacitor is on its way out, if you can whip off the lid look out for bulging/weeping capacitors, if either is observed I suggest switching it off just to be on the safe side.

 

[virnuls]

Thanks - I was expecting it to be something along those lines, but I've been buying hifi equipment since the 80s and nothing has needed a repair before. I'll have a look.