Keith G wrote:
"Stewart Pinkerton" wrote



And this one: 5725720783 (although I've been advised that these are a
teensy
bit *lethal*.. !!! :-)

Yes, but at 400 squids, even I am having a think! I doubt I could even
build that pretty a chassis for that money.................



*Exactly* and if the trannies are at least OK, the rest's all 'bonus'......

From what I have been told (I haven't heard one myself yet) the
transformers are more than acceptable, Ok, I doubt they are up to the
standard of (say) Brian Sowter, but then I don't think many commercial
valve amps amps are, even if they cost ten times as much as this one.

The only problems I have had reported are they are prone to hum, this is
fixable it seems by adding a bipass cap to the first mu stage. I am not
entrily sure why it suffers from hum, or why the bipass would sort it,
but I suspect a proper investigation armed with a scope would get to the
bottom of the problem.

This is the circuit if anyone is interested.

http://www.yogoo.com/xd845t.htm

If I wasn't so commited to the GM70 amp at the moment (and have a pair
of 211's sitting on the shelf for the next one), I would be tempted as
well, Worth it for the transformers alone I would suspect, not to
mention the valves and sockets.

If anyone is looking to try a SET with balls I guess this is a great way
to start.

I have said before to Keith (and added it up) that it would cost
somewhere in the order of £1800 to make a 845/211 amp getting parts from
western suppliers, thats even before making a profit from selling them.

Having said all that, at the moment I prefer the gm70 to the 845, in
comparisons (and yes they were level matched, and yes I was blindfolded)
I prefered the Russion valve to the 845 (esp the copper plate gm70),
though I know the 845 looks better on paper, at least more linear. The
low mu of the 845 does make it a bit of a pain to drive, the mu of 8 for
the GM70 makes it much more flexable. the only problem with the gm70
IMHO, is the 20v 3a heater, makes it hard to use AC without hum
problems, and its quite a challange to get good DC. I would guess
(though I haven't tried yet) that a current regulator would be better
than a voltage one. Doesn't worry me, the 40khz AC heating I mentioned
works a treat. The amps produces as little audible hum as my PP 6550,
which with my speakers is inaudible more than 5cm away from them.

And the fact that gm70's are about £15 each is another plus point :-)

--
Nick