Sorry for keeping you dangling - trying to keep things interesting.
Found the ON/OFF switch. . . .sorry. Whilst fumbling around with my DVD player last night, trying get the thing to play through the amp (it's a pain) I decided to see whether there was a problem with the amp. So I rigged up my Alpha 7 with no improvement. In the box was a mains lead [kettle type], and as it's unused and dust free, rigged it up and. . .Wow! a definite improvement.
Always been such an open sceptic on dedicated power cables, but after hearing such an improvement from a kettle lead, there could be something to this lead lark.
Yes, I'm going to have a large dose of 'humble pie'.