Valve Itch phono

Vin 12,49 & 12,63VDC
What thermal resistance is necessary?

That one is the tallest sink of that series and it should do a good enough job when you need to replace a smaller one for 1-2W more demand on the same footprint. Each of your regs dissipates around 6W with that Vin and the two units two types tubes heaters as load. That sink says 4.5C/W but derate 30% for spot heating and it would be 6C/W ιn perfectly open surrounding to rise 36C above ambient. 3C/W after derating would have been more optimal.
 
No I did not I just said it in general. See for R between bridge and C in Duncan's PSUDII. RC won't ask for yet another reservoir capacitor. 0.9A draw for heating a 12AX7 class and a 6SN7 class bottle per branch. 1.8A total for one in series made winding.