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An Excessively Complicated External Power Supply and Bias Circuit for 807 Amp

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My bottom line on P design for this 807 amp.

Screen supply- I would use 6 0A2- less complicated, highly reliable & inexpensive. Bias- Standard non electronic regulated bias. Simpler design just using capacitors and resistors- less complicated, highly reliable, no noise issues due to extremely low current draw. High voltage- use just enough capacitance with the resistor to rid the top 10 volts of noise & trash for about 2 volts AC ripple output. Nothing more needed for push-pull design. It is a CRC network.
 
So you're saying I should use 6 0A2 (or 0D3) instead of using a pair plus a PAS tube? I already have a bunch of stray 6L6s (not part of a pair), so it's no extra cost. What's the advantage of using that many 0A2s instead?

Also, I already have the 2900 @250V capacitors (soda-can sized Sprague Powerlytics) that I pulled from something, so I was planning to use them up on this project.
 
The GE 6N7 data sheet shows 90V max for H-K.

For the 807 G2 current requirements & the driver the 6N7 will be running +ve control grid. Not the greatest choice for a series regulator. In this cct the Pd max may be exceeded. But it wud work, for a while.

Something like 50 nF across the 0A2s will remove much of the noise. If the cap selected is too large you may have an oscillator!

Not sure where 6X 0A2 would fit in as an alternative. Trying to do series/paralleled? That won't fly, one pair will start & hold the others off. But two 0D3s might be OK.

Am I missing something?
 
Are you assuming that the voltage after the choke would sag significantly from normal 807 screen, and otherwise be so high that the voltage drop across the 16k would cause OA2 current to exceed max rating?
I way I would set it up is 35ma per tube would be exceeded until the 807s draw screen current. That would not overheat and damage the regulator tubes during that short duration. But at the same time guarantee all regulator tubes light. I have seen it designed that way for ham radio equipment.
 
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6L6GC in class AB1 with 450 volts plate and about 300 volts screen draw 6ma each at idle and 22ma at full signal. Use a variable resistor and set 0a2s for about 100ma current draw at 807 screen idle current. At 22 ma screen current per 807 tube, 17 ma of reserve is available from the 0A2s. The 807 may vary from 6L6GC somewhat, but tube internals should be the same as 6L6GC.
 
Yeah, as I got to thinking about it there's no reason for balance pot between the two channels.

Historically I've just copied the bias supply from an amp using similar tubes, although I admit that I've never thought much of it beyond being an adjustable negative voltage supply.

This is the bias supply from the amp I'm currently working on, which seems a little more typical.
Move the 10uF capacitors out of signal path.
 
In your setup, if you had one string of OA2's to provide a common screen voltage for a PP pair of 807, you would set up the OA2 string to conduct a bit under 30mA at idle. At turn-on, once the OA2's strike, the OA2 string would conduct about 40mA until the 807's start conducting (maybe a bit more if B+ was initially high). The average screen current can then increase from idle level by about 20-25mA before regulation is lost.
 
To clear any concerns about the 6N7, that tube is being replaced with a triode-strapped 6L6GC (Or just another 1625... we'll see) in my latest iteration of the schematic.
Other minor change is that the 6J5 and 12BH7 are being replaced by a single 12SN7, and the power tubes are now 1625s instead of 807s. I'll therefore just run a 12V heater all around. Tubes are cheaper, and I'll be pulling less current through the heater wires that will be in the same multi-conductor cable as the B+ and bias voltage. I probably won't be able to use a very heavy gauge for those heater wires, so keeping the current under 3 Amps is a good thing. And not to worry, the Tek transformer has about a million heater windings.:D
 

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Yep- I'll throw it on it's own winding then float the heaters. Not to worry.

Also, it looks like I edited and posted a very old version of my schematic. This is how the feedback was supposed to be connected.
 

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