FWIW: 6922 works pretty well at lower voltages -- like 90VDC or so. new production 6922s from JJ or ElectroHarmonix are good enough for most purposes and inexpensive.
Hi,
Let me try to sort through and answer some of your questions.
The extra 20 V on the tube will move the operating point a bit. If you are curious, you can download the data sheet for the tube and see how much things change.
Tube Datasheet Locator: TDSL Tube search
Frank Philipse's Tube Database: Frank's Electron tube Pages
Both of those are fine. As long as the capacitance of the coupling cap is the same and it can handle the applied voltage, life is good.
For the rectifier, as long as it can handle the applied voltage and current, life is good. Last I checked 800 V > 200 V and 4 A > 2 A, so you're fine there.
You'll dissipate more power in the LM7806 with the higher input voltage. You may need a bigger heat sink there. The LM78xx series have thermal protection built in, so you probably won't fry the chip if it gets too hot, but you'll have your amp turn off periodically if the chip is too hot.
By "The Chip", do you mean the LM3886? If so, ±22 V is no problem. You'll get slightly less power than with higher voltages: 25 W vs 33 W based on rough back-of-envelope calculations. That's a 1.2 dB difference. That's barely audible. Don't worry about it. Enjoy the cooler running amp instead.
~Tom
Let me try to sort through and answer some of your questions.
The extra 20 V on the tube will move the operating point a bit. If you are curious, you can download the data sheet for the tube and see how much things change.
Tube Datasheet Locator: TDSL Tube search
Frank Philipse's Tube Database: Frank's Electron tube Pages
Both of those are fine. As long as the capacitance of the coupling cap is the same and it can handle the applied voltage, life is good.
For the rectifier, as long as it can handle the applied voltage and current, life is good. Last I checked 800 V > 200 V and 4 A > 2 A, so you're fine there.
You'll dissipate more power in the LM7806 with the higher input voltage. You may need a bigger heat sink there. The LM78xx series have thermal protection built in, so you probably won't fry the chip if it gets too hot, but you'll have your amp turn off periodically if the chip is too hot.
By "The Chip", do you mean the LM3886? If so, ±22 V is no problem. You'll get slightly less power than with higher voltages: 25 W vs 33 W based on rough back-of-envelope calculations. That's a 1.2 dB difference. That's barely audible. Don't worry about it. Enjoy the cooler running amp instead.
~Tom
Yeah, I just didn't (and don't) want to have to throw more iron at the problem.
The options suggested by the designer were to use the ~70vdc or so available from the lm3886 rails or supply 65vac for about 90vdc, and in either case this then goes through a 1kohm -> 100uf RC filter for whatever losses i don't care to try to calculate because I'm unsure how much plate current was drawn in the original design with the 6n11.
What I'm planning on currently, what I've simulated in psud2, is using a couple large high voltage soft recovery rectifiers that i already have, and a couple 1000uf 100v caps that i already have, as a voltage doubler across the 50vac or so from the transformer powering the lm3886 side
at about 20ma of combined plate current i should have somewhere just over 100v. with less than 1mv of ripple after it settles. Or i can throw in a $8 hammond choke for way less than 1mv of ripple. Which should do fine for the 6n23p i already have.
I also have some vintage 6dj8 types.
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