Longhorn wrote:
I have noticed that the Peak-to-Peak voltage of the Blu Ray audio out going into the Lacewood is as high as 4V. Can that be overdriving the 6SN7 resulting in the shrillness at high volume levels? Would changing the 6SN7 bias to operate at a different point on the tube's load line possibly help?
You need to stop and think about the design. I seriously doubt that your issues are from overdriving the 6SN7. I think they are because you are overdriving the 6V6 (by a lot!). Let me explain.
In the V2 design, the driver is biased to about 4.0v. It also has a gain of approximately 16 v/v. This means that if you overdrive the 6SN7 by giving it an input exceeding 4.0v, the output voltage would be 4.0*16 or ≈ 64v peak. Now the power stage is biased to about 16v (give or take). This means that at 4.0v into the 6SN7 you'd be overdriving the 6V6 by about 48v. This would cause any power tube to become a little "shrill".
One of the ideas behind the V2 was increased sensitivity. In fact, it one takes about 1v peak to drive the amplifier to maximum output. My guess is that you are seriously overdriving the 6V6 output stage. In fact, in this design it is IMPOSSIBLE to overdrive the 6SN7 without first seriously overdriving the 6V6.
Don't bother with a new driver tube unless it just for tube rolling. Play with some other 6V6s and watch that volume.