1. Why does my amp lose "fullness" when Gain is at 5 or below, regardless of the Master Volume knob position?
2. Does switching from one mode to another (from lo > mid > hi) change the amount of harmonic distortion if the settings (EQ, Gain, and Master on full) remain the same?
3. Does Tilt knob, when set to 10 (which supposedly mimics the Hi treble channel of a Plexi) add additional gain to the overall gain structure (Gain knob + Master volume knob)
4. What frequencies does Middle knob control? Does it boost or cut certain frequencies or just shifts the emphasis of the middle frequency region?
Thank you for your message
The gain control does effect the preamp signal so more gain means more signal. This is why it seems to add body when adding gain. This is why many vintage style amps have a sweet spot.
Reducing the voltage rails around the power amps is the most transparent way of attenuating an amplifier. So there will be no real need to adjust your settings when changing the power. The most obvious tonal difference is from the speaker working more or less.
Yes this will give the tonal characteristics similar to the High Treble channel on our Plexi style amps. It does not add gain but because of the changes in frequencies it has more bite.