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.

TIA

Rob