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Questions about 6BG6G amp build (schematic) Grommes 216BA

I got a wild hair to build "old-timey" monoblock amplifiers from the 1950s, in part because I have a lot of the parts on hand and also because the aesthetic appealed to me. I've had very good luck in my amateur builds of the past couple years. Looking at this schematic I wonder if I could get some advice from the gents here. I have 4 questions:

1. Are there any modern but simple changes that would improve this 1950s design? This is a Grommes 216BA. I won't change the 12AU7s, nor add CCS. My PS will be:
400-0-400>5U4 or 5R4>20uf film 500V>6H choke>40uf 500V>dropping R>20uf>etc. 430VDC B+

2. What does that connection w/ 220K R from 6BG6 plates to the cathode of the driver 12AU7 accomplish?

3. Since I will be using OPTs with 8ohm speaker tap only, how much would I adjust the feedback resistance? I have modern speakers. My OPTs are 5.5Kohm, (w/ no UL taps) though this design calls for 7Kohm. (If I can find 6.6 - 7Kohm OPTs I'll use 'em)

4. Should I use the triode connection shown or supply G2 from a separate ~400V DC source off the B+ line? I am using tube data from old sources, tdsl.duncanamps.

I plan to provide the bias of -40 to 45V from small separate transformer, not the arrangement shown.

Thanks for any experienced advice.


Edits: 05/22/17 05/23/17

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Topic - Questions about 6BG6G amp build (schematic) Grommes 216BA - PeterI 21:02:33 05/22/17 (52)


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