Hey there, I recently brought a tech 21 vt bass deluxe and am initially very impressed. However I have an issue or question. The manual describes the level control as just adjusting the overall output level. However I find on mine that when I turn it past about 12.00 the sound starts to distort. Like a real tube amp yes - but this is Different to what my bass driver DI does. By the time you turn it up all the way it is quite dirty. Is it supposed to do this?