Tube questions....again

[E-Stat]

I don't think I ever got a good answer to my question as to which set of tubes in my pre-amp have the most effect on the sound output. My VAC uses 2 12AU7s (input I believe) and 2 12AX7s for the output-gain.

If you look on their website, you'll find the manual for the CPA-1 which adds a phono stage to the line stage of the CLA-1. The 12AU7s are used for gain and the 12AX7s are unity gain buffers. For that reason, the 12AU7s will have a more profound effect on the sound quality - unless you choose the passive buffered mode. The Manley DAC I use in the vintage system also uses 12AU7s where I have experimented a bit. I really like the sound of 60s vintage RCA Cleartops.

Is it always best to have both sets of matching quality-price range and MFG?

For the gain stage, yes. For the buffer stage, no.

rw