PS Audio BHK preamp owners


Hi

This question is aimed at PS Audio BHK preamp owners regarding the tube bias. I understand that the bias is user adjustable by just moving an internal jumper pin (pretty brilliant). The unit ships with 12au7 tubes set at 4 milliamperes. When the jumper pin is moved the bias is increased to 5 milliamperes. I would like to know if anyone has tried this and if so did you like it? Thank you.

Scot
scothurwitz
This has been discussed on the BHK preamp thread at PSAudio. I’m quite sure that you are supposed to only use the bias setting that matches the tube type: 12au7 gets 4ma; 6922 family, which also includes the 7 volt types, 5ma. I believe Bascom himself mentioned this.
I’ve got mine set to 5ma using a 12v tube, though I didn’t realize it. I had a couple sets of Brimar 12AU7’s that weren’t playing nice with my BHK, I got them warrantied by Upscale. 
I’m running a set of current production “Kevin’s Stash” and Cryo Treated Gold Lion 12AU7’s. Each tube section measures identically to the others, which is not something I’ve seen in matched tubes, except for the Kevin’s Stash grade of tubes. They sound great. 
But I wonder if the higher jumper setting was at least partially responsible for the problems I was having with the NOS Brimar’s. 
What was not going well with the Brimar's at 5ma?  Died early?  Noisy quickly?
I am impressed that in the stereophile review the BHK pre was found to perform very similar to the Pass XP22.