Bridge 20W submin amp

Tube DIY Asylum

Do It Yourself (DIY) paradise for tube and SET project builders.

I was looking at doing this next month.
There are some refinements that need doing of course but the majority of it is there after lots of late nights checking all sorts of obscure details.

As you can see, the bottom pair operates very much as a straight fwd low potential push pull amplifier.
Cascode amps also exist in similar configurations but only single ended.

The main advantage of doing it this way, is the power transformer being driven current drive simultaneously in both halves of the primary instead of the customary "half on half off" see saw arrangement.

This obviously doubles the current, has NO quiescent current in the primary at idle (so you can get a lot more from the core with a lot less saturation problems), and doubles the voltage swing on the transformer owing to the differential (+190/-190V) power supply fed to the amplifier.

The G2 feed is complication in ultra linear mode so at present this is done with a 1:1 coupling transfo for the top valve pairs, but this can also be accomplished with a dual triode as the current is very low.

Moving from Pure pentode to hybrid triode behaviour has the advantage of keeping the high gain but much lower impedance drive to the OPT, as this is only 2K load, but total current flow in the primary is 120m/a at 300+ volts which is quite a bit....

The input/bias circuitry is insensitive to any variations in the supply rails because it's referenced to 0V and controlled by sub min gas discharge devices which also exist like all the other valves from old Russian military stocks...

See what you think!

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Parts Connexion

Topic - Bridge 20W submin amp - ivan_terrible 01:56:42 04/26/15 (7)

RE: Bridge 20W submin amp - ivan_terrible 13:55:29 04/27/15 (5)

RE: Bridge 20W submin amp - ivan_terrible 03:08:21 04/28/15 (4)

RE: Bridge 20W submin amp - ivan_terrible 16:32:11 04/28/15 (2)

RE: Bridge 20W submin amp - bwaslo 23:55:21 04/28/15 (1)

RE: Bridge 20W submin amp - ivan_terrible 04:02:01 04/29/15 (0)

RE: Bridge 20W submin amp - bwaslo 15:52:09 04/28/15 (0)

RE: Bridge 20W submin amp - Eli Duttman 06:45:19 04/26/15 (0)

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