When I had the 834P I rolled many different brands of tubes in this preamp at all positions, including some nice NOS Telefunkens, both smooth and ribbed plates, and finally concluded that the current Genalex 12AX7s, as ordered from Tube Depot and selected for low noise, provided the best results with great dynamics, warmth, air, depth of stage and solid bass. The Telefunkens, though very nice and a close second, were a bit too smooth and soft for my tastes.
