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In Reply to: RE: Screen Voltage - 6L6G/A/B & 6P3S-E ? posted by Triode_Kingdom on May 01, 2017 at 11:16:32
Get the best possible open loop linearity out of full pentode mode, by employing regulated g2 B+. Once g2 B+ is regulated within published limits, you can take some liberties with the anode voltage limit, provided you scrupulously honor the plate dissipation limit.
Eli D.
Follow Ups:
Hi TK, i hope you don't mind if i jump in here as long as it jives with your query, if it doesn't, i will start a new post. I have been looking to try one for awhile but not able to get something that would be suitable for my needs. I am looking for a circuit that can do between 250 and 450v. If anyone cares to share that would be awesome. regards, Dak
Hang a properly rated MOSFET, with its gate adequately clamped from a voltage divider between B+ and ground. Use it as a source follower. Get a 12-position switch from Radio Shack so the resistance of the lower leg can be adjusted( while the amp is OFF ), so g2 voltage can be adjusted quickly.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
DAK, are you referring to a circuit that can be built into an amplifier, or do you mean a variable bench supply (250-450V)? There are lots of circuits around for the latter. Building a supply like that into an amplifier is awkward due to size constraints. Semiconductors aren't generally very reliable at those voltages, although I suppose it can be done. I've never tried, because I usually flesh out new designs on the bench, then use a fixed voltage in the gear.
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Buy Chinese. Bury freedom.
I'm going to disagree. I used MOSFET voltage regulators for B+ as I find it makes for better sound. I basically modded a Nelson Pass design (Nelson only does SS). it worked fine, I retrofitted the amps I had and put it in all subsequent builds. I go overkill when I engineer, so I use MOSFETS rated for more voltage than I think the device will see, and reliability has not been an issue.
Hi TK, i am considering an on amp design like the "maida regulator" or Kevin at K&K, sells one too. I am thinking about giving the K&K one a go on my amp to see if it is worthwhile to do it.
Are you interested in the solid state regulator because it's variable? If I remember correctly, the Maida site states 10%. That's a much smaller window than the 250V - 450V numbers you mentioned earlier. Actually, I'm not sure what the SS version buys you that a little experimentation with gas regulators wouldn't accomplish. Besides, they glow! :)
0D3 and 0A2 (150V): pink/lilac
0C3 and 0B2 (105V): pink
0B3 (90V): purple/indigo
0A3 and 0C2 (75V): orange
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Buy Chinese. Bury freedom.
Initially i was going to go with them and i bought various ones like you outlined, but besides the additional space required i read that tvr produce a fair amount of "noise" or distortion. I am not sure if this is true or maybe circuit dependant, but adding up the pros and cons i now feel that it maybe easier to go with the SS voltage reg. Just a few wires going in and out.
Mike Maida's seminal article is well worth reviewing.
http://www.ti.com/lit/an/snoa648/snoa648.pdf
If you want something with all the kinks worked out, follow the link and pay the man his money.
https://www.neurochrome.com/21st-century-maida-regulator-rev-2-0/
Eli D.
This is a nice regulator! I have used these in the past, well worth the cost!
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