I purchased the 12AT7 version of the VTA ST-70 kit in mid-2009. I alternate preamps - but prefer my tube based unit. The problem I'm having is that there's just too much drive into the amp. Essentially, I can't move the preamp volume control (of any of my preamps) much past the 9 o'clock position - about 1/4 rotation. And that's with a turntable as the input device. You can imagine how little vol. control rotation I have when the input device is a CD player! I want to use the preamp volume pot. in a more linear region - closer to the 12 o'clock position.
My Question: Can I experiment with using 12AU7 tubes on the front end of the ST-70 - but WITHOUT altering the 8 resistors on the circuit board?? I mean, will I harm anything by doing this? (By the way I have Bob's input attenuator control for the ST-70. For now, though, I prefer to work with the input tube configuration.)
Appreciate any feedback.