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.
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