I just finished a series regulator for amps that require a stiff negative supply. I have a couple friends building GM70 amplifiers and i thought this would be a welcome addition.
Ideally you would connect rectified and smoothed 230VAC to the inputs.
The schematic is based on the supply from the Tek567 tube O'scope
Pass tube is a 6080/6AS7 or pin equivalent.
The long tailed pair ECC88 runs into a PNP transistor VAS. This gives a large amount of amplification.
Any thoughts?
Once im happy about the boards i will post the gerbers for free in my gerbers thread.
Ideally you would connect rectified and smoothed 230VAC to the inputs.
The schematic is based on the supply from the Tek567 tube O'scope
Pass tube is a 6080/6AS7 or pin equivalent.
The long tailed pair ECC88 runs into a PNP transistor VAS. This gives a large amount of amplification.
Any thoughts?
Once im happy about the boards i will post the gerbers for free in my gerbers thread.
Attachments
I've used a Maida regulator (a la Joe Curcio) for a negative regulated supply. Just use a PNP HV transistor and reverse polarity of caps and diodes in the circuit. It's very stable and the dropout voltage is much less than the tube reg you posted.
I guess so, but i have a friend that likes using up his 6336's this way. And he happens to have plenty of 230VAC toroids available to feed the circuit
For -150V, I use a 0D3 as a shunt regulator 🙂 This is a very interesting idea if you need gobs of bias current though 🙂
Luckily, even my triode strapped sweep amps only need -90V. I start with -200V, and use a 150V zener as a shunt reg into a 0B2 tube also as a shunt regulator for -90V.
Luckily, even my triode strapped sweep amps only need -90V. I start with -200V, and use a 150V zener as a shunt reg into a 0B2 tube also as a shunt regulator for -90V.
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True, although I thought that drive current came from the driving stage (source follower or whatever). I've only built A1/AB1 so the current required is just whatever flows through the grid leak resistors.
Gobs of bias current? For A2? Gobs of positive grid current, sure, but neg biasing surely not.
And why stabilized g1 voltage without consideration on how to obtain a kV or so stabilized anode voltage required by the GM70?
g1 biasing stabilization reference must be taken in relation to the anode, either both are in the correct relation (defined by the actual dc amplification factor) stabilized or non of them is.
Surely this neg. supply must be intended for something else than biasing...
And why stabilized g1 voltage without consideration on how to obtain a kV or so stabilized anode voltage required by the GM70?
g1 biasing stabilization reference must be taken in relation to the anode, either both are in the correct relation (defined by the actual dc amplification factor) stabilized or non of them is.
Surely this neg. supply must be intended for something else than biasing...
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Yes, the idea was to connect the current sinks for the DC coupled cathode follower to the -150V rail. That is why it is beefy.
As for the 1KV regulator, im currently thinking about that. My current thought process revolves around a PL519 in tetrode as a pass element, and either a maida style regulator. Or a cascode FET to drive the op amp.
One problem i see is that when tetrode connecting the PL519 you need another 120V tap on your transformer to provide the floating screen supply.
I will open another topic on the matter.
As for the 1KV regulator, im currently thinking about that. My current thought process revolves around a PL519 in tetrode as a pass element, and either a maida style regulator. Or a cascode FET to drive the op amp.
One problem i see is that when tetrode connecting the PL519 you need another 120V tap on your transformer to provide the floating screen supply.
I will open another topic on the matter.
I know we like tubes but aren't you afraid that building an amplifier with so many tube modules will turn it into some kind of behemoth that needs a forklift to move it around?
That's what wheels are for. But this doesn't weight nearly as much as the extra iron required to do LC filtering for the negative rail. And yes it takes up amp real-estate but it also has a bit of a cool factor.
Next up: GM70 pass device regulator to regulate the 1KV B+😀😀
Next up: GM70 pass device regulator to regulate the 1KV B+😀😀
He also has a delay board which only engages once the negative bias is at an appropriate level, I believe it was already posted in his free gerbers thread. At least that's what I'll be using for my GM70 build regardless of whether I use this tube based board, better safe than sorry.