spwyatt wrote:

I've just been lucky enough to have purchased a pair of the stunning
Rogers/BBC LS5/8 speakers, complete the with a pair of the BBC modified
Quad 405 frequency splitting amps (actually, one 405 and one 405-2...
no idea why!)

The main problem is that both amps exhibit a low level but perfectly
audiable mains hum - even with their gains right down and nothing
plugged into the (XLR) inputs. Am I right in thinking it's reasonably
easy to fix by changing some capacitors? Any help greatly appreciated!!

Any 405 is pretty ancient by now. You should consider replacing all the
electrolytic caps.

Graham