Well, I think the goal, is to get the tubes to flood in as much as you can without creating distortion. Each Op-amp is a little tiny bit different. The more you "lessen" the trim pots (counter clockwise) the colder the sound. The more you open them up, the warmer and more open they sound (tubes...voltage..not sure). You can do it with your earphones on and with the unit on with a tiny screwdriver. Tune it by ear. You'll be able to hear when it starts to distort, then dial it back. If you are at a point of balance now, make a note of where your trims are at then incrementally increase each pot the same amount. If you get out of balance, you'll hear it. You may be out of balance to begin with since I don't know how well they tune these from the factory. Again, you'll have to trust your ears. And when I say incrementally, I mean like an 1/8 - 1/4 turn of the trim pots. Adjusting these does make a big difference. From the factory, mine were turned down about a 1/4 on the low side. My guess would be it's on purpose so as to not get any complaints of distortion or extraneous noise.