"Nick Gorham" wrote in message
. uk...
Hi,

Given its been a bit quiet on here, I thought I would post some of DIY
output.

Here is a link to some pictures of the GM70 amp that I have been working
on for the past eight months.

http://www.lurcher.org/nick/images/gm70/

Circuit is a C3g Pentode voltage amplifier with VR tube screen regulator,
then 300b driver to 1:1 amorphous interstage to GM70 grid. Output TX 7k
amorphous. Driver and 300b supply, series regulator using 6080, ecl82 and
0d3 (Steve Bench inspired). TJ-Meshplate 300b, running 330v @ 55ma. Copper
plate GM70 running 1020v @ 110ma.

All transformers by Automatic Electric Europe.

Rough specs, -3dB points (5w into 8ohm) 18Hz, 52kHz. 3% distortion reached
at 42w into 8 ohm.

It was designed to drive a set of large panel electrostatics, but I have
been using the breadboard version driving a pair of Yamaha NS1000's. My
normal 94dB/W speakers are slightly overpowered for them :-).

I can't take too much pride in them, as their owner did the construction
and I did the design and internal build. But I am still very pleased how
they have come out.


Hi Nick,

Thanks for the excellent pics of your GM70. There seems to be a shortage
of ongoing projects these days - and those that are fettling are too busy to
write about it:-)

Your thread quickly got hijacked and turned into a learned discourse on
X-rays.
Perhaps ukra was not the best place for it.

Nevertheless, keep up the good work:-)

Iain