Second bit of advice - get together a list of the (approx.) 467394549 different codes that are the same as, or VERY near to ECC83s, such as 12AX7, 5751, etc. etc. etc. etc..
If the OP is still around: the 834P was designed for three 12AX7/ECC83 tubes (these are identical tubes). Stay with these. I have been rolling tubes in and out of my 834P for ten years and have seen no improvement using any other type, in particular the most frequently recommended alternatives, a 5751 in V1, and a 12AU7/ECC82 in V3. My current configuration is EI ECC83 in V3 and V2, and a Rogers 12AX7 in V1. It sounds wonderful.
This thread has just prompted me to swap the bias resistors at V3 to better suit the ECC82 I'm running in that position.
Thanks to GT and Jez for the nudge.
The standard value was 68K which I measued as giving 1.3mA.
I had 22K and 10K to play with.
22K gave about 3.9mA and 10K gave about 7.8mA
I fitted the 22K (3.9mA) on the reasoning that I already liked the sound with the 68K/1.3mA combination.
Very happy to change the values if you recommend different?
OK, thanks for the info Jez.10K should be best out of those but use at least a 1W resistor. The original 1.3mA is about what the ECC83 tops out at but absolute max rating for 82 is a whopping 20mA!
Check that the voltages to other stages isn't effected too much by the much higher current draw.
An audio friend had a standard 834P and the sound of it is still in the audio memory a truly musical phono stage.
I've had the 834P for about 10 days, and I continue to be amazed at just how big a difference it has made to the enjoyment of vinyl. It replaced a nice solid state phono stage from Graham Slee that I had been happy with, until I heard the EAR. The presentation is so different, in a very good way; it just sounds more interesting, real, and above all, musical. Mine is standard, and truth be told, I'm in no hurry to roll tubes through it at this point.
It sounds better and better as time passes...more dynamic, richer, and more engaging, and it seems that this could/should continue for a while yet. Fun times...