On Tue, 19 Jun 2007 13:37:37 +0100, Nick Gorham
wrote:

Eeyore wrote:

Andy Evans wrote:


Sounds like this is for a preamp, and in this case Phil is right on
the button. A couple of toroids back to back are perfect. If you use
230 to 12v and 12v to 230 you can not only take 12v AC for the heaters
but also rectify it to -15vDC for a constant current sink if you're
using a differential pair. But allow for enough current capacity and
seperate the toroids to allow for some cooling - be careful to check
the result for overheating.


I found this on Farnell. It's a 1:1 capable toroid

http://uk.farnell.com/jsp/Electrical...sp?sku=3919997

Forget it, it's no longer stocked but it ought to be possible to get 1:1 types.

Graham


The only UK source for low vol 1:1 I have found is

http://www.antrimtransformers.com/

But in this case, the 1:1 doesn't also supply the heater voltage which
two back to back 230v:6v TX's would do.

I always found that for making low signal measurements on tubes it was
a good idea to supply the heater from a battery. Did away with all
sorts of mains hum nasties.

No good for a final design, of course - but that's another question.

d

--
Pearce Consulting
http://www.pearce.uk.com

On Tue, 19 Jun 2007 13:31:00 GMT, (Don Pearce)
wrote:

I always found that for making low signal measurements on tubes it was
a good idea to supply the heater from a battery. Did away with all
sorts of mains hum nasties.

No good for a final design, of course - but that's another question.

Agreed. A lead-acid accumulator is much better. ;-)

This brings back fond memories of my Beethoven Portable radio. This
had valves to die for and was powered from batteries - one for the HT
and a 'grid bias' battery which supplied around five different
voltages.

The output valve had a terminal on the top (from memory, the anode) in
addition to the terminals at the base. It was around 15cm tall.

--
Chris Isbell
Southampton, UK

"Chris Isbell" wrote in message
...
On Tue, 19 Jun 2007 13:31:00 GMT, (Don Pearce)
wrote:

I always found that for making low signal measurements on tubes it was
a good idea to supply the heater from a battery. Did away with all
sorts of mains hum nasties.

No good for a final design, of course - but that's another question.

Agreed. A lead-acid accumulator is much better. ;-)

This brings back fond memories of my Beethoven Portable radio. This
had valves to die for and was powered from batteries - one for the HT
and a 'grid bias' battery which supplied around five different
voltages.

The output valve had a terminal on the top (from memory, the anode) in
addition to the terminals at the base. It was around 15cm tall.



Last time I saw the Leicester Invester he had a big pile of bright
yellow industrial batteries that he intended to use to run a valve
amp..???

Chris Isbell wrote:
On Tue, 19 Jun 2007 13:31:00 GMT, (Don Pearce)
wrote:


I always found that for making low signal measurements on tubes it was
a good idea to supply the heater from a battery. Did away with all
sorts of mains hum nasties.

No good for a final design, of course - but that's another question.


Agreed. A lead-acid accumulator is much better. ;-)

This brings back fond memories of my Beethoven Portable radio. This
had valves to die for and was powered from batteries - one for the HT
and a 'grid bias' battery which supplied around five different
voltages.

The output valve had a terminal on the top (from memory, the anode) in
addition to the terminals at the base. It was around 15cm tall.


Thats annoying, I am now trying to find what the battery output valve
was with a top cap.

I am thinking of the likes of PT15 or 807, but neither of those are
"battery" valves.

--
Nick

"Nick Gorham"

Thats annoying, I am now trying to find what the battery output valve was
with a top cap.



** The 1B8-GT was popular in battery portables.

http://www.nj7p.org/Tube4.php?tube=1B8GT



........ Phil

Phil Allison wrote:

"Nick Gorham"


Thats annoying, I am now trying to find what the battery output valve was
with a top cap.




** The 1B8-GT was popular in battery portables.

http://www.nj7p.org/Tube4.php?tube=1B8GT



....... Phil






Ah, yes, that would make sense, single ended pentode output stage.
Thanks Phil.

--
Nick

"Chris Isbell" wrote in message
...
On Tue, 19 Jun 2007 13:31:00 GMT, (Don Pearce)
wrote:

I always found that for making low signal measurements on tubes it was
a good idea to supply the heater from a battery. Did away with all
sorts of mains hum nasties.

No good for a final design, of course - but that's another question.

Agreed. A lead-acid accumulator is much better. ;-)

This brings back fond memories of my Beethoven Portable radio. This
had valves to die for and was powered from batteries - one for the HT
and a 'grid bias' battery which supplied around five different
voltages.

The output valve had a terminal on the top (from memory, the anode) in
addition to the terminals at the base. It was around 15cm tall.

A colleague of mine has just such a radio (though not a Beethoven
portable) with two lead-acid accumulators.

It also has a three-position preset tone control marked
"Speech", "Music" and "Jazz" :-)

Iain

In article i,
Iain Churches wrote:
It also has a three-position preset tone control marked
"Speech", "Music" and "Jazz" :-)

My parents had a radiogram where the tone controls were labelled 'bass'
and 'brilliance' They were rotary switches rather than pots and appeared
to be high pass and low pass filters only - no boost. Wonder when Mr
Baxandall produced his near universal design?

(My spool cheeker didn't recognise Baxandall so knowing you picky lot I
did a Google on 'baxandall tone control'. And the first hit was pages
written by 'our own' Jim Lesurf...)

--
*Fax is stronger than fiction *

Dave Plowman London SW
To e-mail, change noise into sound.