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

"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! ;-)

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

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

TWICE?

Should be close(r) to 4 times.


Martin
--
M.A.Poyser Tel.: 07967 110890
Manchester, U.K. http://www.fleetie.demon.co.uk

"Fleetie" wrote in message
...
"Chris Morriss" wrote
Just a hypothesis, but I bet 'BLT' puts the amp into bridged mode, making
a mono amp of twice the power.

TWICE?

Should be close(r) to 4 times.


Martin
--
M.A.Poyser Tel.: 07967
110890
Manchester, U.K.
http://www.fleetie.demon.co.uk


You could be right here - the meters (OK ...) go up to 400 watts. I can't
find any specs on this amp - the mk.1 was 75 watts stereo and curiously
frequency at 1w - 0Hz - 200kHz?!. So far I've bottled at 2 watts with Dynie
1.1s and put any idea of a subwoofer on hold - and that's before pressing
the 'loudness' button (happy days!).

Rob

"Chris Morriss" wrote in message
...
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

Excellent Chris - that'd make sense and worth a check. Thanks.

Rob

In message , Rob
writes

Excellent Chris - that'd make sense and worth a check. Thanks.

Rob



Can you just go and check the lettering again?

It might say BTL and not BLT, in which case it would stand for 'Bridge
Tied Load'.
--
Chris Morriss

"Chris Morriss" wrote in message
...
In message , Rob
writes

Excellent Chris - that'd make sense and worth a check. Thanks.

Rob



Can you just go and check the lettering again?

It might say BTL and not BLT, in which case it would stand for 'Bridge
Tied Load'.
--
Chris Morriss

Bugger - sorry! BTL it is. Thanks Chris. It's just food food food with me.
I've jut googled it and it seems to mean a form of bridging -correct?!

Rob

"Keith G" wrote in message
...

"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! ;-)

:-)

It would actually *make* a good skip, it's flippinnormous. And with its 6
phono settings plenty of fiddlage ahead. Will it survive a tube shootout ...
tbc!

Rob

"Rob" wrote in message
...

"Keith G" wrote in message
...

"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! ;-)

:-)

It would actually *make* a good skip, it's flippinnormous. And with its 6
phono settings plenty of fiddlage ahead. Will it survive a tube shootout
... tbc!


Heh heh! I haven't seen a 'tube shootout' since the time I trod on me
Autosol Chrome Cleaner when I was cleaning the motorbike I had at the time!!
:-)

Damn, I've made meself glum now! (No bike for a year or two now..... :-(