• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Understanding this "Dynaco 6V6 Push-Pull Amp" circuit + cathode bias in the same

Greetings friends. I got a pair of PCBs off eBay that claim to be a "Dynaco 6V6 P-P" circuit and I'm trying to understand how it works, and hopefully build an amp around it. Here's the schematic offered by the vendor:


So a pair of EL84 in P-P, cathode biased, driven by a 12AX7 in a common cathode config, perhaps known as a Floating Paraphrase.

How can I determine the output of this circuit? The PCB has "10W" printed on it...can I get away with a 10w OPT, or should I go beefier? According to Dynaco literature, we're looking at 13.5v at the cathodes, 370 on the plates and a shared 130ohm cathode resistor.

I'd like to build this amp with an ANTEK AS-1T250 PT. It features 4 secondaries total, 2 for HV and 2 for heater power, so I plan to wire each channel with its own windings. Here's a rough schematic:


I'd like to keep the costs down on this one, so the cheaper 10w OPT from EDCOR is more appealing than the 25w model. Obviously the cheapest config would use a single power supply shared between both channels but I can splurge on two, if there would be any noticable improvement. Still cheaper than a Hammond PT and a tube rectifier.

Thanks for taking a look!
 
A power transformer only has to provide the proper voltages, and proper current, while staying cool, reliable, and safe.

An output transformer IS the window between the music signal, and your loudspeakers.
How low of a frequency, and how much power at low frequencies do you need?
Except for cost, weight, and size; the low frequency power capability is the Major difference between an Edcor 10W and Edcor 25W output transformer.
That is true with a 6V6, it is true with a 6L6.

If you ever want to use the output transformers for more powerful tubes than the 6V6, 6BQ5, EL84, etc. (instead, use tubes like 6L6, KT66, EL34, 7591, KT77, etc.; then the 25 watt output transformer gives more possibilities.
Of course, using those more powerful output tubes requires a more powerful power transformer.

Always a tradeoff.

I did not look up the specifications of the Antek power transformer; But you will get perhaps 30, 40, 50, or 60V more B+ if you use solid state rectifiers, instead of tube rectifiers.

Changes require more changes.

That old Dyna circuit is pretty good; positive synergy.

Have fun designing, building, and listening!
 
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