Hi everyone, Appreciate any help on this one. I've got an AU555a with an intermittent noise, independent of input or volume/ tone controls. The best way i could describe it is kind of like an arcade machine special effect- sort of like a ticking distortion that comes and goes, sometimes it's distant and faint but distinguishable, other times it's very noticeable. Actually does anyone remember the interference you'd sometimes get through a speaker when you're receiving an SMS on your mobile phone? Maybe something similar to that. I've separated the pre and power amp section and i can still hear the noise through headphones. I've also unplugged the tone control board to find the noise still there. (though this probably serves no purpose as the pre amp was seperated anyway but thought i'd mention it). I'll also note this though it's likely a separate issue - the amp isn't silent when idling. There's a kind of background hiss, very faint, but i notice that it is amplified when increasing treble. Thanks for any help - the amp is on the bench i've got basic stuff to tinker with, soldering iron, solder sucker, component tester, dmm etc.