It's actually hard to describe; the amp itself works absolutely fine, which is great for its age. However, when I turn it off, after a few seconds I can hear a "squealing" of sorts out of some speakers, starting at quite a high frequency and decreasing. It only lasts a few seconds, and there are no humps or any other issues. Is that most likely the capacitors draining, and is it something I should get fixed? It doesn't sound like something urgent to be honest, though I'd imagine that given its age, a re-cap would be good for it anyway. Would I have to replace all of them or just the four big caps? Thank you!