Regulator/Choke/Cap

[Jesse]

Hello Tubeguys,

I'm planning to build a tube pre with ss HT regulator.

For the B+ supply, will it be benificial to install a choke (10H) right after the regulator, followed by a big cap (470uF) with some small PP caps?

There seems not such combo on net. Is this kind of combo useless? (Or even degrade the performance of the PSU?)

Thanks!

Jesse

[Mikael Abdellah]

I'm probably more inexperienced in this than you are, but i would suggest to try the Duncan PSU-designer. It's really a great software that has opened my eyes.

[Jesse]

Hello Mikael,

Thanks!

I have tried the sofeware. It's a great tool, I agree.
But, unfortunately, the regulator is not on the filter type list.

My idea is:
1. It is likely to have some noise coming out from the ss regulator, so a choke may help to remove those noise.
2. to stablize the B+ voltage better.
3. Two choke/caps sets in parallel to provide B+ for two channels separately.

I'm not a electrical-based guy, so this idea can be wrong. Any input will be appreciated.

[Brett]

If you only have one choke, put it before the regulator. Better still is an LC filter rather than a CLC.

For your SS reg, don't use a series reg. They stink. I've tried about a dozen varieties and none are any good. Most use a variation of the simple series pass transistor, or 3 pin regulator (7812, LM317,LT108x) series sitting on top of a stack of zener diodes. They all have poor regulation, an output Z that rises a lot with frequency within the audio band and are noisy sods.

Use a shunt reg instead, even if it's a simple glow diode stack. A proper active reg is even better.

http://www.euronet.nl/~aespreng/Shuntregv11d/Manual.pdf
Almost a meg in size.

[ste]

do you mean rectifier rather than regulator?

[Jesse]

I mean voltage regulator, not rectifier.

[Brett]

I forgot to add, in the filament supplies of my PP813 amp (10V at 10A per channel), I use a couple of chokes after the main series regulator with a small shunt between them to keep the series reg fully on. I do it to ensure any switching hash from the regs is gone as the filament in a DHT is as sensitive as the grid and any noise there will be amplified. In this setup, the peak signal current swing is small compared to the overall filament current.

[ste]

Sorry, forgive my confusion. Wouldn't a choke following a regulator get in the way of the regulation?

[Brett]

Originally posted by ste
Sorry, forgive my confusion. Wouldn't a choke following a regulator get in the way of the regulation?

The regulation isn't critical, though the voltage has shown itself to be dead stable on the CRO. It's about controlling the hash from the SS rectifiers (even though I use Schottkeys), and keeping it from the filaments of a DHT tube.