Adrian C wrote:

Perhaps, you were overdriving the inputs without realising you are doing
so? Or negative feedback circuitry component values have drifted and you
are listening to a loverly bit of crossover distortion? Maybe the output
transistors are going... but 10 years? I wonder if controls and switches
are introducing non-linear effects of their own making.

Update if anyone is still watching.

There is a real problem with the Amp on the balance control. Play with
the balance and one channel will cut in and out. Weird. So the Amplifier
is not 100%. It will need replacing at some point. Which is a pity as I
have an emotional attachment to it!

The distortion was most noticeable before with the DVD as the source
passing straight into the Aux input.

What I have now done is put all my inputs through my mixer, and reduced
the level of the input signal to the amp. This is from CD players, DVD
for video and the Digital TV.

It may be my imagination, but I am pretty sure that if I then turn the
Amp up to compensate I do not get the same distortion from the Tweeters
I was getting before. At first I thought maybe the match between Amp and
Speakers was bad at the high end (I seem to have read of such things),
but this does not make sense as a degradation over time. It is as if the
Amp cannot handle a normal input levels without distortion at the high end.

Does this make any sense?

It is hard to ask for second opinions as most friends say 'Your system
sounds so much better than my PC speakers' ...

Assuming I was to buy a new Amp is £300 worth spending with the quality
of my speakers?

Eddie