The stock tubes are really good for new made tubes. I run NOS, CV4024/12AT7 and VT99/6F8G RCA grey glass flat plate. David Berning has been around for a long time. He made one of the only preamps I know of that you could bias the tubes. I never had one as they were hard to find but he has always been ahead of the curve on his designs.
7/3/15 at 5:06pm