• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Regulator for Tube Power Amp

Here's a circuit I use

I use this to regulate the preamplifier section of a modified Fairchild 255a amplifier. Basically the adjust leg of an LM317 is lifted above ground via a zener string. The other zener and transistor prevent the LM317 from having to see a voltage differential in excess of its design limit. The project can be seen at <p> www.tech-diy.com/fairchild_255a.htm although I never finished writing all the html
 

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Brett

Member
2002-01-07 6:02 pm
Higo said:
I think that a string of zeners can not be all quiet. Zeners are noise sources...
Marcelo.
Yep. The first regs of this type I saw were the Jung ones published in and around the POOGE articles in Audio Amateur in 1980. They were noisy then, and they're noisy now.

So, my suggestions for regulator circuits would be
- Allen Wright Superreg
- John 'Buddha' Camilles shunt reg published in Valve

- these Tubecad articles
-- Tube Voltage regs 1: http://tubecad.com/may99
-- part 2: http://tubecad.com/june99
-- part 3: http://www.tubecad.com/july99/
-- Hybrid regs: http://www.tubecad.com/march2000/
-- Inverted Tube Shuntregs: http://www.tubecad.com/january2001
-- 300B as reg: http://www.tubecad.com/articles_2001/the_300b_reg/

- Legacy amplifier and reg by Thorsten Loesch: http://www.thunderstoneaudio.nav.to/ . Scroll down to Legact amp, and beware the popups.
- JC Verdier's article in Sound Practices: http://jcverdiervalvevinyl.online.fr/2300B/tech300B.html

and of course to aid in any PSU design, a copy of the free PSUD from Duncan Amps is worth it's weight in gold.
http://www.duncanamps.com/psud2/index.html

That should keep you busy for a while.
Cheers
 
mozfet,

http://www.vacuumstate.com/preamp.htm

It is called a cookbook for tube pre-amp circuits. I will disagree with the title. To me an electronics "cookbook" has basic topologies and the relevant formulas that pertain to the circuit under discussion. This book is stark in it's use of formulas.

He does have an engaging writing style and there is plenty to learn.

As for the topic of this thread, the author makes 2 very interesting points about regulated power supplies.

1) Use a shunt regulator. (as opposed to pass device) Read the book to find out why.

2) Use choke loaded (as opposed to cap loaded) power supplies. Read the book to find out why.

Aud_Mot
 
Re: I will remember to tell Mr. Johnson

Two of the previous posts directly or indirectly point to Allen Wright's SuperReg circuit. I plan on using these (1 per channel if i can afford it) to power my PP EL84 amp. Since the EL84 doesn't draw too much current, with enuff heatsink one of these is able to power a PP Stereo amp.

It has been used, abused, tested, and bashed, and has evolved into something quite outstanding.

Read the book. It is good -- not only for its technical content, but for insights and humour too.

dave
 

Brett

Member
2002-01-07 6:02 pm
Re: Re: I will remember to tell Mr. Johnson

planet10 said:
Two of the previous posts directly or indirectly point to Allen Wright's SuperReg circuit. I plan on using these (1 per channel if i can afford it) to power my PP EL84 amp. Since the EL84 doesn't draw too much current, with enuff heatsink one of these is able to power a PP Stereo amp.
Me too. I got a full set of ST35 trannies yesterday, and I want to do a small EL84 PP class A, for the mid-high horns. I have a board in development to do the shuntreg using Allen's circuit, so I can implement a suprreg per channel on the EL84, and a superreg per driver and output stage on the PP1Cs (4 in total).
I know the PA774 power trannie won't deal with the load of the regs too.

It has been used, abused, tested, and bashed, and has evolved into something quite outstanding.
Could you tell me more about your design please Dave? Or post a schem? I'd be interested to see what you're doing with the EL84, which seems to be a tube people either love or hate. I'm quite fond of it, and when triode strapped, has nice curves. It's not a DHT but good.

I'm working on
Va = 250V
Ia = 40mA
Vg = -8V
Rk = 210R

My pre won't have any trouble driving it to full output, without a driver stage.

Read the book. It is good -- not only for its technical content, but for insights and humour too.
Agreed.

Cheers
 
Re: Re: Re: I will remember to tell Mr. Johnson

Brett said:
Could you tell me more about your design please Dave? Or post a schem? I'd be interested to see what you're doing with the EL84, which seems to be a tube people either love or hate.

1st amp will be either a PP1C based EL84 amp, using a set of Cryoed 6922s i got from Perkins, using iron & chassis from a Scott LK48 or an SE amp based on a set of very large OPTs i got out of an East German colsole (complete w fake fireplace - which is now on the set of a TV show in Vermont) crossed with a power supply from a Baldwin Organ and a 6N1P driver - i'll probably base it loosely on one of the Decware amps, but i'll have a dual triode as a driver for each EL84 so that i have room to play.

After i have wet my teeth on that, i have enuff iron to do a dual-mono SCA 35 based PP1C.

Exact schematics will depend on what B+ i end up with.

I'd like to end up with 6 channels of EL84 to drive my mains, another 4 SS to drive my woofers, and another 4 to drive the HT subwoofer (sort of built into the floor). And then there is the assembly of my RTP, and design & build of the active XO. Hopefully i can get it all done in the next couple years or so... them roun' tuits are just so prolific.

dave
 
tube regulated power supply for PP EL34 power amp

Hello,

I would like to know if anyone has any ideas, suggestions, links, diagrams, etc. on an absolute no compromise fully regulated tube power supply for an 80W/channel PP EL34 tube power amp. The power amp uses 8 EL34/channel with dual 7119 tubes for the input/driver stage. The amp is transformer coupled with an input voltage splitter transformer and is tube rectified using damper diodes. There are separate power and filament stages for both the input/driver stage and output stage. The amp delivers about 30W/channel before moving into Class AB1. I would just like to try this to so how it compares with the unregulated power supply already being used.