tony sayer wrote:
In my earliest work days I designed colour TVs. We had an X-Ray
detector permanently covering the bench, because if the line output
valve got a few too many volts, and a bit too much current, its anode
would start to glow red, and X-Rays would come flooding out.


Wasn't that the shunt stabiliser that did that?.

Hence the metal can in some sets?..


Yep, like the PD500, but that would normally be running a bit higher
than 1kv AFAIK.

--
Nick

"Don Pearce Posturing Pommy Prick "


In my earliest work days I designed colour TVs. We had an X-Ray
detector permanently covering the bench, because if the line output
valve got a few too many volts, and a bit too much current, its anode
would start to glow red, and X-Rays would come flooding out.


** Absolute ********.






........ Phil

Phil Allison wrote:

"Don Pearce Posturing Pommy Prick "


In my earliest work days I designed colour TVs. We had an X-Ray
detector permanently covering the bench, because if the line output
valve got a few too many volts, and a bit too much current, its anode
would start to glow red, and X-Rays would come flooding out.

** Absolute ********.

Quite.

X-ray emission requires a certain *energy level* that has ZERO to do with
glowing anodes.

Graham

On Aug 7, 10:11 am, Nick Gorham wrote:
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.

--
Nick

Very nice indeed, Nick. We'll have to drum you out of the club for all
those heresies -- pentodes indeed! series regulators, gee! -- but I'm
sure your amp sounds brilliant precisely because of them.

Andre "Real Men Shunt" Jute (1)
Visit Jute on Amps at http://members.lycos.co.uk/fiultra/
"wonderfully well written and reasoned information
for the tube audio constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site
containing vital gems of wisdom"
Stuart Perry Hi-Fi News & Record Review

....regulate, that is. To join the ultrafidelista, next to every tube
shove up a bigger power tube to shunt its current. For those who were
educated too long ago to remember shunt regulation, and who haven't
"read" anything except Playboy since, shunt regulation consumes half
the power, so the shunt tube must be capable of handling twice the
desired operating current.

Andre Jute wrote:


...regulate, that is. To join the ultrafidelista, next to every tube
shove up a bigger power tube to shunt its current. For those who were
educated too long ago to remember shunt regulation, and who haven't
"read" anything except Playboy since, shunt regulation consumes half
the power, so the shunt tube must be capable of handling twice the
desired operating current.



Yep, shunting is certainly a good solution, howver over the last six
months, I think I can get within 90% of the sound of a shunt with 20% of
the complexity.

--
Nick

On Aug 9, 11:59 pm, Nick Gorham wrote:
Andre Jute wrote:

...regulate, that is. To join the ultrafidelista, next to every tube
shove up a bigger power tube to shunt its current. For those who were
educated too long ago to remember shunt regulation, and who haven't
"read" anything except Playboy since, shunt regulation consumes half
the power, so the shunt tube must be capable of handling twice the
desired operating current.

Yep, shunting is certainly a good solution, howver over the last six
months, I think I can get within 90% of the sound of a shunt with 20% of
the complexity.

--
Nick

I'd love seriously to suggest shunting every tube with a big powertube
but I think those days are past. For myself, the simplicity of two-
tube channels is very seductive.

Andre Jute
Visit Jute on Amps at http://members.lycos.co.uk/fiultra/
"wonderfully well written and reasoned information
for the tube audio constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site
containing vital gems of wisdom"
Stuart Perry Hi-Fi News & Record Review

"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

There seems to be a shortage of ongoing projects these days - and
those that are fettling are too busy to write about it:-)

Could be - I'm building my best amp yet for a client. Or to be
precise, two monobloks. Outputs are 2a3 into O-netics iron. Amp is
balanced right through the three stages. First stage is a diff pair of
01A with constant current sink, direct coupled into a 26 driver stage
which is in push-pull into a Lundahl LL1660 interstage. Lots of solid
state in the low voltage supplies for the filaments of the DHTs and
the CCS, - LM337, LM1084, BC549 etc - and lots of Schottky diodes.
Power supply is 47uF electrolytic, 10H choke, 80uF polypropylene, 10H
choke, 40uF polypropylene, 1.5K resistor, 40K polypropylene. Quite a
complex build, including designing the layout in a pair of 2U
rackmount chassis.
As for valves, the 26 globe just beat the 112A gobe as a driver -
fuller and more mellow. But there were a few good input choices - 30
globe, 201A globe, 112A globe. even the humble 31 didn't disgrace
itself.
Sound is extremely nice - full and mellow but with air and good
treble. Very detailed. Client is very pleased, and now I have the
design (which took WEEKS to finalise, research and build) I can build
more rather more quickly. However, the parts count is pretty
frightening and you don't get much change from ?1000 quid. It could be
built cheaper with cheaper iron and coupling caps instead of the
interstage, and cheaper valves - those globes are hard to find and
match and they all have to be imported from USA with the appropriate
customs charge and handling.

Just a bit different from the average Chinese amp!