[gurevise]

All,
0.47mf C12 capacitor is in filament filter circuitry.
It helps to keep filter impedance low at high frequencies, where C13 and C14 are a bit inductive as any big electrolytic capacitor.

I think that by having C12 in parallel with C13 and C14 makes current charging spikes worst. Meaning, rectifier diodes open and close at higher speed to charge C13, C14. If C13 is removed, then we’d use some parasitic inductance of C13 and C14 to smooth out current change cycles. This, making saw-tooth like voltage on C13 and C14 smoother.  By reducing current spikes we'd help to make phono-stage quieter.

What do you think?

Thanks
Sergey

[hagtech]

Yes, C13 helps the rectifiers open and close faster.  That is exactly its purpose.  It is very small so that is does not really take much current to slew them.  Really, run the calcs,

i = CV/t

it adds nothing to the spikes.  It does, however, give a bit of a low impedance for the rectifiers to turn off.  There is an stored junction charge that must be removed for the diode to stop conducting.  C13 speeds that process up.  Sometimes you will see caps across each of the diodes, does basically the same thing.

jh