Just came across your schematic and post today. My two cents are as follows:
In the main audio circuit, I would simply reduce the circuit's grid-stopper resistance values some as follows:
R2, input tube, from 240 ohms to 220 to the 208 ohms region. R5, the 2A3 tube, from 240, go to 120 ohms, and NOT lower than 115.0 ohms. Rhoderstein MK-3s ( NOT ever PRPs!! ) can sound good there. I really LIKE the BPC-16 where you have it, I ordered the medium NI ones from Mikey last year, a very very nice part. I LIKE a two-stage 2A3 amp too !!
In the supply, much redo is needed:
The 5U4GB is OK, but I would really want to viciously pare-away at all the ugly series resistances, which are harmful to the musical presentation, AND use a double pi choke input filter, preferably one that does not meet critical inductance at the standard convention of 60 HZ.
So, Chris, totally eliminate R8, R9 and R10. Eliminate the 15 uF input cap and also sadly, the very nice MQ 06-008 inductor.
After the 5U4GB, connect to a double pi filter as follows : L1/C1/L2/C2. L1 and L2 can both be the Triad C-40X at under $11 from Allied Electronics on line, C1 and C2 can be from 47 to 50 uF, either round canned ASC oils or the 47 plus 47 @ 500 VDC Black Gate WKZs if your budget allows.
A power transformer with a different secondary will NOT be needed!! Here's why: Your cap input usually produces a VDC B+ of 1.41 times the VAC of the P.T.'s secondary, minus the rectifier drop . A Triad C-40X in the L1 position ( DCR 10 ohms, 320 mHY ) will have about 1.35 times ratio of the VAC of the P.T.'s secondary. But you are also eliminating 238 ohms of UNWANTED DCR, which will help to restore the .06 difference in multipliers !!
Consider these humble power supply suggestions, as you are eliminating 50 ohms ( R8 ) plus 88 ohms ( L1 ) plus 100 ohms ( R10 ) in your schematic's supply ( 238 ohms total ) , and obtaining to a supply of only 10 plus 10 ohms, ( 20 ohms total ) ie: 1/13 th the DCR !! That redesign WILL positively and absolutely creme the original supply from purely a listening-to-music point of view.
Minor final points, you may want to ( or have to ) increase the value of R11 slightly upward, maybe another 100 ohms or so, for a little more filtering to the input stage. Keep C6 at 50 uFs or less, film !! Use heavy duty and highest-quality ground wires. Keep your input wiring ( RCA jack to input tube grid ) short.
Please do let me know if you execute this, and exactly how good it sounds. Bet 'ya a dollar if 'ya built and heard it, there would positively be no returning to the original schematic's power supply ever !! Oh well. Cheers.
Jeff Medwin