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.

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