5e3 Fixed Bias Balance Modification with High Voltage AC Tap

[rundgrenrules]

My 5e3 build has always been pretty humm-y. I started tying to diagnose the cause of the hum, moving wires with a chopstick and whatnot, checking grounds, etc. Nothing really made the annoying 60hz hum go away until I popped in a pair of near perfectly matched new production 6V6 tubes to replace the (what I did not know at the time) were pretty out-of-match RCA 6v6s.

I popped the Bias Rite in and checked the idle current for the RCA tubes and it was 17mA off from one tube to the other. One is glowing blue and much hotter to the touch than the other. I pop in the new Tung Sols and they are within .01 mA idle current of each other and the hum is GREATLY diminshed.

I would really like to use the RCA tubes and add a circuit to bias, balance (and un-balance) the power tubes.

Would this one work just fine? (from Rob Robinette's site - see attachment below):

I don't want to lose the characteristic of fixed bias 5e3 sound but I want to be able to use these (or any other unmatched) power tubes. It calls for a 50V AC tap, but my PT doesnt have a 50V tap. The amp is built from a Trinity Kit (see the layout at the bottom). So that means I would need to maybe add a high voltage tap like this one (again from Rob's website - see attachment below):

And COMBINE the adjustable fixed bias circuit with balance pot WITH the High voltage tap bias circuit....and now I am thoroughly confused.  Could someone point me in the right direction or help me mash tehse circuits together?  Thanks for reading!

[rundgrenrules]

I guess this would work?  220K resistor to drop the voltage coming off the AC on pin 6 (+-380v)?

[TonyM]

I used this mod successfully in my JCM800 2204 50W build but I ran dual bias pots. Initially I had a 68k resistor to allow me get the correct bias range.

As I had a lot of noise due to my failure to recognize I has a 270ohm resistor instead of a 2.7k resistor on the V1 valve cathode and was also creating a scratchy guitar pot because V1 wasn't bias correctly.

A floating AC heater circuit was installed to reduce hum and noise which was very successful but the floating circuit changed the bias range which then required a 56k resistor to allow the output valves to be biased a little hotter.

The 56k resistor goes straight to ground from the pots.

[acheld]

But, why?

You fixed the problem with matched tubes. 

You MAY introduce new problems with a more complicated biasing scheme.

Best solution is to use your NOS tubes for a couple of Champs!

[dude]

If you want to use the RCA unmatched tubes, why not just use a separate cathode bias resistor and cap for each 6V6..? Do the math on each tube using the correct value cathode R to balance the tubes draw. I would think changing to fixed bias, your 5E3 is no longer a 5E3.