Dear XLR8OR,
Assuming you are using stock tubes(PCC88 & 12AX7) in EAR 88PB & 864.
Assuming EAR 88PB's volume no need to exceed 12 o'clock when directly pushing ARC power. (Note: using EAR 88PB as pre-amp may NOT work in all systems though I found it is my cup of tea)
I have auditioned EAR 912 and 88PB as writing some audio reviews a year ago. I have some ideas about 864 though not under a test environment. Here are what I found:
1) EAR 912 phono section would "generally" outperform 88PB(using 912 line stage) especially if I couldn't tailor-make extra short, high quality ICs. I believe you have similar situations(if not problems) when using 88PB as phono hooked into 864's line pre-amp...
2) EAR PCC88 amp circuits sounds more accurate, better resolution, have more high end air, more dynamics than its 12AX7's. Note: EAR 88PB are FETs and PCC88 hybrid circuits and totally different from its 12AX7 circuits.
3) In order to get best results from using 88PB pre-amp, I had/have to do some tube rolling. In my system, the first 3 stock PCC88 have been replaced by Telefunken whilst the last one remains the same. Tim told me in August those are NOS Ei productions. Different brands of tube sounds different.
4) If you're looking for more "transparency" at the top, better high frequency extensions, etc, you may try some Siemens E83CC or Tele ECC803.
5) I don't really understand "The 88PB sounds warmer and more accurate but at the same time sterile and lean in comparison to the weight, transparency, liveliness and depth of sound stage on offer from the 864’s phono stage." But it doesn't matter as I believe you will have different results with different gears, say, if you have Benz Micro Ebony(but not Concerto), Conrad Johnson power amp(but not ARC)...right;)?
6) I agree "tube rolling 864" is the best option for you at this moment.
Best regards
Dan
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