• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

PSU shunt capacitor selection

I have a preamplifier based on 4 identical SRPP stages per channel (E88CC ~ 6DJ8). Recently I replaced the coupling capacitors to PIO and I am thinking of replacing the B+ shunt capacitors close to the tubes, as well. I read somewhere that the SRPP topology is sensitive to power supply quality, because it has very low PSRR. Now, the main capacitors are 1000 uF/450 V flash electrolytics (two per each tube), and I use WIMA MKS-4 1 uF/630 V capacitors next to the tubes. Would it give any audible improvement if I replaced them to PIOs? I have some spare 0.22 uF/400 V PIO capacitors, are they not too small? B+ is around 310V, and Io = 5 mA per tube. The load resistance calculated from these is 62 kohms. The time constant would be then 13.6 ms, giving a corner frequency of around 12 Hz. The shunting of the capacitor is effective above this frequency. Is this correct? Please advise.