🚀 go-pugleaf

I have a Yamaha C2a pre-amp which has become noisy over the years. The
noise is on all inputs at any position of the volume control except almost
fully off. It does not increase as the volume is turned up. The noise can
vary but starts after about 15 minutes from turn-on and sounds like a high
pitched kissing (that's right, purse your lips and make the highest
frequency kissing sound possible) and a sharp intermittent crackle at
other times, one one channel. I have had Yamaha work on it a couple of
times, and they have replaced a few components but basically they can't
find the fault. I have been told that this is a fairly common problem with
ageing C2a's. But I love the darn thing. It has one of the best moving
coils stages I have ever used. In perfect working order, its my all-time
favourite pre-amp. Does anyone have any suggestions for tracking down and
fixing the fault?