Compactron Regulated Power Supply

denny9167 · 2011-12-03 3:45 am

Has anyone tried this particular power supply for any projects?

artosalo · 2011-12-03 9:58 am

The possible probelm with this circuit comes from the low amplification factor of the triode of 6JZ8.
The PSRR of the whole regulator is only some 33 dB at best.
If the triode were hi-mu type like 12AX7, the PSRR would be more than 10 dB better.
The regulation of the output voltage is also better with hi-mu triode.
The PSRR can be improved some 10 dB by connecting a 220 nF capacitor between the output of the regulator and the grid of the triode of 6Jz8.

For most applications 6JZ8 works surely well enough.
I have used similar circuit, but built with 6L6GC and 6AU6.

denny9167 · 2011-12-05 12:07 am

artosalo said:
The possible probelm with this circuit comes from the low amplification factor of the triode of 6JZ8.
The PSRR of the whole regulator is only some 33 dB at best.
If the triode were hi-mu type like 12AX7, the PSRR would be more than 10 dB better.
The regulation of the output voltage is also better with hi-mu triode.
The PSRR can be improved some 10 dB by connecting a 220 nF capacitor between the output of the regulator and the grid of the triode of 6Jz8.

For most applications 6JZ8 works surely well enough.
I have used similar circuit, but built with 6L6GC and 6AU6.

Thanks for the suggestion, would it help to use a VR tube instead of the neon bulb?

211hojbjerg · 2011-12-05 1:49 am

Hi reg's
it is correct that you can improve by using a hi mu triode, however a pentode ca give you mu of 1000-1500, EF184
you can improve just by connecting the pass tube as a pentode, with well regulated g2.
I use EF184 and EL34 im mu reg psu, both connected a pentodes.

best regards
karsten

artosalo · 2011-12-05 7:15 am

Thanks for the suggestion, would it help to use a VR tube instead of the neon bulb?

VR tube is OK, but why not a simply a zener diode (48 V...).

Tom Bavis · 2011-12-05 7:00 pm

A way to put those 17JZ8s to work...

6LU8 or 6MF8 is the same pinout and has a higher mu triode, higher power Pentode too.

denny9167 · 2011-12-19 1:47 pm

I'm curious the tube data sheet says the maximum plate voltage of this tube is roughly 250V,and yet isn't their at least 300V being applied to the anode of the feed through tube?

SY · 2011-12-19 2:07 pm

That rating is for plate to cathode.

Miles Prower · 2011-12-19 8:24 pm

denny9167 said:
Has anyone tried this particular power supply for any projects?

Yep.

My design uses the same basic topology, however, I'd bet mine performs better. A single triode for the error amp isn't going to give very much open loop gain, and will compromise the closed loop error correction, and therefore, the voltage regulation. That's probably OK, if you don't need tight regulation, but that's OK for a basic, adjustable bench supply.

For good performance, you need better in an active screen regulator, both in regards to voltage regulation and Zo -- both of which improve with increasing open loop gain.

For a 40V variation in DC rail voltage, this regulator showed an output voltage variation of 0.8Vdc for the required 270Vdc for the screens of Class AB1 807s.

Not too sure about using a neon panel lamp for the reference, as these aren't rated for a lot of current. A voltage regulator VT or a voltage reference VT would be a better choice.

denny9167 · 2011-12-19 9:03 pm

I appreciate all the input, just finished the power supply,with excellent results. I'm using it to power a tube based buffer preamplifier,requiring only 150V B+. The sound is marvelous!!!!! Dead Quiet!!!!!

denny9167 · 2011-12-19 9:11 pm

Miles Prower said:
Yep.

My design uses the same basic topology, however, I'd bet mine performs better. A single triode for the error amp isn't going to give very much open loop gain, and will compromise the closed loop error correction, and therefore, the voltage regulation. That's probably OK, if you don't need tight regulation, but that's OK for a basic, adjustable bench supply.

For good performance, you need better in an active screen regulator, both in regards to voltage regulation and Zo -- both of which improve with increasing open loop gain.

For a 40V variation in DC rail voltage, this regulator showed an output voltage variation of 0.8Vdc for the required 270Vdc for the screens of Class AB1 807s.

Not too sure about using a neon panel lamp for the reference, as these aren't rated for a lot of current. A voltage regulator VT or a voltage reference VT would be a better choice.

Really nice!!!

denny9167 · 2011-12-22 9:42 pm

Here's a pic of the power supply. I wired it to a 6DJ8 buffer preamp curcuit I've also been working on,and the sound is superb,with zero noise!!!!

artosalo · 2011-12-23 8:23 am

Looks nice and really compact. Congratulations.

denny9167 · 2011-12-23 4:45 pm

artosalo said:
Looks nice and really compact. Congratulations.

Thanks

v4lve lover · 2011-12-24 8:58 pm

211hojbjerg said:
Hi reg's
it is correct that you can improve by using a hi mu triode, however a pentode ca give you mu of 1000-1500, EF184
you can improve just by connecting the pass tube as a pentode, with well regulated g2.
I use EF184 and EL34 im mu reg psu, both connected a pentodes.

best regards
karsten

would you mind sharing a schematic . im building all these regulators at the moment . and i want to see if a pentode really gives better characteristics as a 6080

have a good one

denny9167 · 2011-12-31 6:42 pm

v4lve lover said:
would you mind sharing a schematic . im building all these regulators at the moment . and i want to see if a pentode really gives better characteristics as a 6080

have a good one

Here is the actual schematic of the board shown,Thanks

denny9167 · 2011-12-31 6:49 pm

I've stumbled on to one problem that I hope someone can help me with. I had mentioned in a previous post that the supply worked great,well that was with only +140VDC,which is all that my preamp curcuit requires,but I decided to use the recommended input voltage,which is roughly 300-350V,and I was only able to adjust to +150VDC,and I was wondering what could be causing this,it says it will regulate to 250V? Thanks

Kay Pirinha · 2011-12-31 7:02 pm

Hi folks,

in all schematics shown here in this thread the pass through tubes work as triodes! So regulation behavior should be comparable to real triodes, such as e.g. 6080.

To get the advantages of a pentode pass trough, such as much lower voltage loss across anode and cathode, you will have to add a auxilliary source to feed the screen grid, which is connected between cathode an screen of the regulation tube.

Best regards!

denny9167 · 2012-01-01 1:10 am

I'm thinking the neon bulb is the culprit here?

quinnling · 2012-01-01 5:44 pm

I've been using the regulator on post #1, and is able to regulated to 250v. I have been using the regulator on a phono preamp (RCA Circuit) and recently with an Aikido line stage. Works without any issues.

What is the voltage you getting across the Neon lamp ? If I remember correctly (Big chance that I may not) ... I was reading a little bit above 90v

Compactron Regulated Power Supply

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