I'm appalled by the number of DC power supplies I have to build to
feed the filaments of the DHTs I use (directly heated triodes), which
need one supply per tube ideally. I'm using up loads of voltage regs
in the process, and wondered which ones "members of the panel" favour.
Typical supply is a 60VA 0-12, 0-12 transformer, then on each
secondary Schottky bridge, 15,000uf cap, 12v voltage reg and an
adjustable reg confugured as a current source. Typical requirement is
7.25v at 1.25A (10Y), but there's also 2.5v at 1.75A (46) and 5v at
1.25A (300b).

I'm using LM1084 at present, but sneaking in some 78S12 because
they're cheaper. LM1084s have gone up recently, so also interested in
cheaper suppliers than Farnell.

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.

Andy Evans wrote:

I'm appalled by the number of DC power supplies I have to build to
feed the filaments of the DHTs I use (directly heated triodes), which
need one supply per tube ideally. I'm using up loads of voltage regs
in the process, and wondered which ones "members of the panel" favour.
Typical supply is a 60VA 0-12, 0-12 transformer, then on each
secondary Schottky bridge, 15,000uf cap, 12v voltage reg and an
adjustable reg confugured as a current source. Typical requirement is
7.25v at 1.25A (10Y), but there's also 2.5v at 1.75A (46) and 5v at
1.25A (300b).

I'm using LM1084 at present, but sneaking in some 78S12 because
they're cheaper. LM1084s have gone up recently, so also interested in
cheaper suppliers than Farnell.

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.

Dare you use a switching regulator ?

Graham

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. :-)

So I have tended to use variations on the kind of topology shown on

http://www.audiomisc.co.uk/Armstrong/700/730PSU.gif

As you can see, the zener sets the nominal voltage, and a capacity
multiplier pass device smooths over the noise and gives a slow start/stop.

That example was for about +/-20V up to about 100mA, used for the rails in
a preamp. But the same topology has been used many times by my old research
group for voltages in the few V region at currents up to a few amps, so may
serve your purpose. [1] Just alter the components to suit. Make the pass
transistor a form of darlington pair if needed. I found a single device was
usually fine for currents of the order of an amp or two. But if you need
high current the single-pack darlingtons made for cheaper SS amps might
well do that well if you wanted. But these may need to be checked for
oscillation problems.

Main advantages of the topology are low noise and a gradual windup and
rundown rather than coming on or going off with a crack. Kinder for your
valve heaters, perhaps. You may also like the fact that it has no overall
feedback. :-)

No idea if it will suit you, but since you mentioned my name...

For power amps, though, I always just used a decent transformer and large
caps, then designed the amp to reject power line variations. So no need for
any active smoothing/stabilisation/regulation.

Slainte,

Jim

[1] e.g. for the PSU for 5-12V 1A Gunn diodes where noise from the PSU
needs to be minimal as it would introduce noise sidebands to the 94GHz
output. If you want I can see if I can dig out a diagram of the variable
and fixed versions used for that, but they are in essence the above.

--
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

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.

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 , 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

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 , 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

"Jim Lesurf" wrote in message
...
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. ;-

**"Carcinotron"? I had to look that one up. A type of travelling wave tube.
I thought I'd heard all the names, but the choice of the name: carcinotron
was sure an unfortunate one.

Trevor Wilson