On Jan 17, 8:20*am, "David Looser"
wrote:
"Andy Evans" wrote in message

No virtue in batteries, and a pig to implement. I have tried, but a
good current source sounds just as good as long as you can get the hum
right down.

Heavy filamented DHTs were comonly run from raw AC in the old days so I
don't know why you think you need to keep the hum "right down". Valve
filaments should really be supplied from a voltage, rather than a current,
source. The only advantage of feeding them with a current source is that it
reduces the switch-on surge, but again with heavy filaments that really
isn't an issue.

David.

Quite. I wrote a long screed on this subject and then trashed it as
counterproductive to Andy's purpose. The ultrafidelista generally use
AC fils because they sound best, and if they want to regulate the
plate voltage, use a constant current loaded shunt regulator made with
a bigger tube next to each power tube. But Andy's on a learning curve,
and he won't know that all this regulation is a bridge too far -- I
mean the danger of creating an over-refined tube amp that sounds just
like a silicon amp but more expensive so -- until he hears it and
starts backing off to where he likes the sound. You gotta do it for
yourself; that's part of the fun.

Andre Jute
Arrival is merely the start of the next journey

On Jan 16, 7:29*pm, tony sayer wrote:
In article , Jim Lesurf jcgl@st-
and.demon.co.uk scribeth thus

In article
,
Andy
Evans wrote:

So - which voltage regs are your fave choices here? Good quality output
important, but cost also a consideration. This looks right up Jim's
street for starters.

FWIW I tried various types of 'IC voltage regulator/stabiliser chip' some
years ago and decided I wasn't keen on any of the common types. Too prone
to oscillations or excess noise, etc. Newer ones may be better, but I lost
interest in using them. *:-)

Shouldn't you valve types be using DC from batteries;?...

There are some who do. They hate capacitors so much, they design the
entire amp with transformer coupling, and use batteries for power.
It's all a question of your commitment to the purity of your sound --
and how many banks of car batteries your wife will let you stack up in
the living room. My understanding is that the fellow in Switzerland
who drove his anodes with batteries is no longer married.

Andre Jute
Thumbs well clear of the bricks

"tony sayer" wrote in message
...
In article , Jim Lesurf jcgl@st-
and.demon.co.uk scribeth thus
In article
,
Andy
Evans wrote:


So - which voltage regs are your fave choices here? Good quality output
important, but cost also a consideration. This looks right up Jim's
street for starters.

FWIW I tried various types of 'IC voltage regulator/stabiliser chip' some
years ago and decided I wasn't keen on any of the common types. Too prone
to oscillations or excess noise, etc. Newer ones may be better, but I lost
interest in using them. :-)


Shouldn't you valve types be using DC from batteries;?...

--
Tony Sayer



Yes - be like my grandfather and toddle off the the local garage once a week
to get the accumulator recharged. It somehow seems to fit the ethos of using
directly heated triodes 100 years after they were superceded.

In article
,
Andy
Evans wrote:
Thanks Jim - I'll look at this solution. Were you thinking something
like a TIP50 device? I have a box full, so that would be handy for lower
currents. What would be good for 2A and over (say up to 5A rating)?

Did you try the LM1084 types? I guess you didn't like the 78 types and
the 317.

Afraid I can't recall enough details to say. Too long ago that I did the
work, and then simply settled for my 'favourite solution'. Not built a PSU
like it for some years now. Most recent ones were by my old research
students. :-)

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.audiomisc.co.uk/index.html
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html

In article , tony sayer

wrote:
In article , Jim Lesurf jcgl@st-
and.demon.co.uk scribeth thus
In article
,
Andy Evans wrote:


So - which voltage regs are your fave choices here? Good quality
output important, but cost also a consideration. This looks right up
Jim's street for starters.

FWIW I tried various types of 'IC voltage regulator/stabiliser chip'
some years ago and decided I wasn't keen on any of the common types.
Too prone to oscillations or excess noise, etc. Newer ones may be
better, but I lost interest in using them. :-)


Shouldn't you valve types be using DC from batteries;?...

The only valves I've done PSUs for were klystrons or carcinotrons. I
suspect the battery stacks for those would have been quite large. ;-

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.audiomisc.co.uk/index.html
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html

"Andy Evans" wrote in
message


if you want really good regulation,
you still can't beat the venerable LM723.

Note that I really need an absolute minimum of 2A current
handling, so LM723 is out and LM317 is too marginal -
tubes need between 1.25 and
1.75A.

LM323 is rated for 3 amps.

LM 338 is rated for 5 amps.

No virtue in batteries, and a pig to implement. I have
tried, but a good current source sounds just as good as
long as you can get the hum right down.

Agreed.

Trevor wrote:

**The LM317 is as good as the 1084, but, if you want
really good regulation, you still can't beat the venerable
LM723. More inconvenient, but still one of the best
performing regulators at reasonable price. For my money, I
like the LM317/337 regs. Very cheap, easy to use and v ery
high performance.

Not very efficient though. Valve amps make enough heat
without adding a source inside the chassis. Something with a
lower dropout voltage would be good.

Also wondering why the OP configures the filament regulator
as a current source. More efficient for many filaments
because they can be stringed in series, but I can't see why
it's better, for a single filament, to use a high-impedance
supply.

Ian

Ian Iveson wrote:
Trevor wrote:


**The LM317 is as good as the 1084, but, if you want
really good regulation, you still can't beat the venerable
LM723. More inconvenient, but still one of the best
performing regulators at reasonable price. For my money, I
like the LM317/337 regs. Very cheap, easy to use and v ery
high performance.


Not very efficient though. Valve amps make enough heat
without adding a source inside the chassis. Something with a
lower dropout voltage would be good.

Also wondering why the OP configures the filament regulator
as a current source. More efficient for many filaments
because they can be stringed in series, but I can't see why
it's better, for a single filament, to use a high-impedance
supply.

Ian



The reason I do it that way is it sounds better. I believe the reason it
sounds better, is some of the signal appears across the fill in a DHT,
and the voltage reg will try and regulate that away, with a current reg,
the signal is common mode, so not affected.

Voltage reg certainly sounds worst than AC heating, but I think current
reg is as good as AC without the problems of AC.

Just my theory of course, so expecting to be wrong.

--
Nick

Andre Jute wrote:

The ultrafidelista generally use AC fils because they sound best,

Because hum is good for fidelity ?

Graham

Nick Gorham wrote:

Ian Iveson wrote:

Also wondering why the OP configures the filament regulator
as a current source. More efficient for many filaments
because they can be stringed in series, but I can't see why
it's better, for a single filament, to use a high-impedance
supply.


The reason I do it that way is it sounds better. I believe the reason it
sounds better, is some of the signal appears across the fill in a DHT,

If some of the signal appears across the filament then the regulator isn't
doing its job.


and the voltage reg will try and regulate that away, with a current reg,
the signal is common mode, so not affected.

UH ?


Voltage reg certainly sounds worst than AC heating, but I think current
reg is as good as AC without the problems of AC.

Just my theory of course, so expecting to be wrong.

How utterly bizarre !

Graham