Now we know...

[Filterlab]

Why Musical Fidelity can slash their prices so low:

Somehow I think not!

[Prince of Darkness]

If it's based on the A1, then anyone building should invest in big heatsinks. The MF's ran very hot and had a poor reliability record as a result.

[Filterlab]

Yeah, somehow I don't think it's quite the same circuit.

[greenhomeelectronics]

In my garage I have a spare cylinder head for a 3.2 litre Jaguar straight 6. I think it would make a perfect heatsink for an A1. Might need a 35 horsepower fan as well - just to be on the safe side :-) I have never known an amp run so hot, if satan had an amp it would have to be the A1. It would save him a fortune on his gas bills :-)

[Filterlab]

They do run exceptionally warm, most people think they're a Class A design you know.

[Prince of Darkness]

Here's a picture of an A1 power section for comparison.

[Vinyl Grinder]

Why Musical Fidelity can slash their prices so low:

Somehow I think not!

Starange u mention him as i bought one of these:

http://cgi.ebay.co.uk/NE5532-HI-FI-S...742.m153.l1262

I think those pots will hit the rubbish bin first of all..

[Vinyl Grinder]

They do run exceptionally warm, most people think they're a Class A design you know.

The shitty 'A1' i had, all the paint blistered off the top was slightly bowed aswell...I think someone must have left it on doing nothing for some time.

[WikiBoy]

Here's a picture of an A1 power section for comparison.

You should never put standard electrolytics so close to such a high intensity heat source. The tantalums are fine but the electrolytics will dry out over a couple of years and might explode. There are electrolytics designed (especially in computer applications) to take this level of heat but they are about four times more expensive.

Curiously because it is a highly biased class AB (like the Krell and some others who call themselves class A) it will run cooler flat out than at half volume or at idle (quiescent). A *real* transistor class A is different and is represented in the UK by Sugden. Of course you get valve class A's like the Puresound A30 and they don't have these problems or design constraints as a valve is basically a voltage amplifiers where as those output trannies in the picture are configurated as current amplifiers and current = heat.

[WikiBoy]

You should never put standard electrolytics so close to such a high intensity heat source. The tantalums are fine but the electrolytics will dry out over a couple of years and might explode. There are electrolytics designed (especially in computer applications) to take this level of heat but they are about four times more expensive.

Curiously because it is a highly biased class AB (like the Krell and some others who call themselves class A) it will run cooler flat out than at half volume or at idle (quiescent). A *real* transistor class A is different and is represented in the UK by Sugden. Of course you get valve class A's like the Puresound A30 and they don't have these problems or design constraints as a valve is basically a voltage amplifiers where as those output trannies in the picture are configurated as current amplifiers and current = heat.

(Addenda) If I remember rightly the circuit was designed by Tim P of EAR fame and he always called it class AB, it was just the marketing dept of MF that called it class A. He also designed it *with* the more expensive caps