I have a SE34I.2 with stock rectifiers, Russian Mullard el34 and 6N23P drivers. The speakers used were Decware HDT.
I decided to measure the transfer function for power and phase before and after the mod. The signal was taken directly from the output transformer in parallel with the speakers. Only the left channel is shown.

The first graph is for the switch in the position "less bass". Yellow is before the mod, cyan is after.




The second graph is for the switch in the position "more bass". Pink is before the mod, green is after.




Note: the pictures represent the difference between the control and test signals, the absolute value has no meaning here. Only deviation from the straight line matters.
The listening experience in general confirms the visual representation. The sound stage became more up-front, did not notice much difference in clarity.

Steve,

the graphs have been updated. I see almost no static difference before and after the mod. However for both cases the instantaneous dispersion of the transfer function for power and phase was quite substantial (up to 10dB and 240 degrees) during listening especially in the bass region (below 250 Hz). I cannot however imagine how it can contribute to more or less clarity and true dynamics.

No worries, I just mean that I updated the graphs after I removed the resistor. The original graphs were done with the resistor in place.

Instantaneous dispersion is what I see on the live graph when I disable averaging. Both graphs are stable from about 250Hz and up; and below that frequency I can see substantial instantaneous swings both in power (up to 10dB) and phase (up to 240 degrees). The character of those swings might change the perceived spatial information and dynamics rendering(?).

I can hear changes in the sound stage, it became more up-front. In an orchestral recording I did myself the instruments stick out more than I remember in the live feed.

When I have time I will probably measure the amplifier loaded with a resistor instead of the speaker to see if there are any differences. With the HDT load it is only a 40-20000Hz (+-3dB) amplifier with a big phase distortion below 250Hz.

I soldered in the caps last night and can confirm that I perceived an improvement.

My reference cartridge (only a Denon 103 but it kills my Ortofon 2M Red) is being repaired, so I resorted to CD and the alternate cartridge.

Since getting into vinyl, I don't listen to as much CD, but the mod has made that more pleasurable, at least in the 2 hour post upgrade listening session.

Simon

I've used metallized polyprop caps in both my SE84CS and also my old refurbed ST70 (because that's what I had).  I used a couple of old "wonder caps" in the SE84CS, and inexpensive xicons in the '70.

The results of this mod, or tweak, is nothing short of astonishing, in my mind. My Select (SE84CS) sounds incredible, as if it had far more power and oomph than before. The whole musicality spectrum went through the roof compared to any other mod or tweek I've experienced. No other tube swapping or signal cap upgrades, et al, had anywhere near the benefit.

The results with my old (but refurbed) Stereo 70 were similarly astounding, as the same mod is possible given EL34 tubes.

I'd personally save the Rusky pio's for another project, and get a couple xicon .1uf's as they're only around a $1 apiece and are relatively small and easy to fit in.

One disadvantage to the Rusky pio's and their large size is this; you'll need to be bending the leads around to situate them, and  those thin brittle steel leads can break off as you massage them to fit in place.

Karl

ps- I'll add that the suppressor grid and cathode were already directly hard-wired on my old Stereo 70, and the difference between this and the "CCE" mod was nothing short of astonishing!

Yes, Dan, and the improvement was very dramatic...

Karl

If you can, look under the board and determine where pin 3 and pin 6 of the op tubes are, and then look to see if there is a trace connecting those pins. If there IS a trace connecting them, then that is the trace to be broken.

It's as though there were a wire connecting pin 3 and pin 6 (but here the wire is replaced by the trace) and you wanted to replace that wire with this little .1uf capacitor.

If there is NO trace connecting these pins, then you're free to just solder the cap between pin 3 and pin 6 with no other considerations.

Hope this helps...

Karl