At the moment I am working on a friend’s Quad 405-2. It has never been serviced and is well over 30 years old. Electrolytic capacitors have a limited lifetime, mostly 2000 hours, special ones more (the ones I am using for replacement have a lifetime of 7000 hours plus). They gradually degrade sonically and may even break down completely, some of the ones coming out of my friend’s amp are bulging and leaking electrolyte (like an old cell battery). You won’t necessarily hear the degradation as it is gradual and so is hard to notice but it’s there. I listened to his 405 before starting work and found it to be quite lifeless and muddy, nothing clean, just a smear of sound. Hopefully once finished the difference will be audible (I’ll let you know). I have a theory of my own about this which I will write about in a later blog.
I will publish which web sites gave me the information for the upgrades.
This is just a quick post as I have a cold and my head feels full of old, used car grease. Might even go and have a lye down!