Let the rolling start.
(PSA, rolling is costly and never ending. Also, what works for me and my tastes, and more importantly, my gear, might not work for you.)
NOS RCA Black pate 12AU7 (1960s)
This is not super ideal as i don't fully have a handle on what the stock tubes sound like. But i had never planned to used them. Brimar CV4003s are coming next week.
These will be used in the gain stage (front two) which has the biggest impact.
Question, what happens if you end up with mutli pairs of tubes that you've been testing in the gain slots?
Yes, can you still use then in the driver stage (the other 6 tubes.)
That said, you'll watch to match them up - In the EVO 400, that would be V9/V14, V10/V13, V11/V12 (these are the gain tubes in the middle.)
Question, If i'm using HT bypass, do the gain stage still have any impact? ie, aren't i bypassing the pre?
Yes they still have an impact. The gain stage is still active with you're using the HT bypass, it just circumvents the volume control and that input is set to unity gain.
Here is the PL compared to the RCA.
I thought they might be the same-ish.. but they are not.
(the two on the right are PL 12AU7)
They look like el-cheapo Sino 12AU7 tubes. ugh..