In message , Keith G
writes

"Rob" wrote in message
...
Hi - I wonder if anyone can shed some light on the operation of a Hitachi
HMA 7500 mk2 pre/power amp:

1. It can connect through two in/outputs - direct and 'condenser
coupling'. Anyone any idea what this coupling thing is?

2. There's a switch on the front of the power amp labelled 'BLT' - when
it's switched in the speakers switch off. 'BLT' is also marked on the LH
direct input on the power amp, and the meters have a range marked BLT, at
double the watt markings of a scale beneath. Any idea what that's all
about (apart from sandwiches)?

3. 1 side of the power amp gets very hot directly above the heatsink - the
RHS on this photo:
http://tinyurl.com/5eqne

I realise this is close to the transformers, but the heat is very local
and *very* hot - probably hotter than the casing of a class A valve amp.
The LHS is warmish, more your tepid warm. I've had a nose about inside and
I can't see anything obviously fried or about to fry, and I've tried
switching the inputs and speakers around - same result.



Drop this mutha in the skip where it belongs and put another record on
instead! ;-)






Just a hypothesis, but I bet 'BLT' puts the amp into bridged mode,
making a mono amp of twice the power.

--
Chris Morriss