Audio Horizon Pre Owners - Tube recommendations?

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Greetings, Audio Horizon pre-amp owners. I know you're out there. ;)

I have one of Joseph's earlier models (TP 2.0 i) which I'll likely be upgrading soon. Shortly after purchase, I replaced the stock tubes with Amperex PQ White Label 6922s, and never looked back, running them for several years. Sadly, I've noticed a problem with some tubes (clearly failing in some manner), and have moved back to the stock EH tubes... which sound like crud.

I don't do much tube rolling, so I have a few questions:

- What have been your favorite tubes in the TP?

- Where did you source them?

- Is there any place where I can send my Amperex tubes for testing, to see how much life/power/mojo might be left in them?

I'm sure this question applies to any tubed gear. Even if you don't own an AH, I'm sure your input will be most appreciated!

Thanks,
Rob