Power Amp Tips

"Hair" tip from Cliff Chase

The "hair" around notes is due to the non-linearity of the power amp. Just using the preamp you get the crunch but you don't get the hair as the notes decay and when picking lighter. The power amp is also responsible for much of the dynamic response.

You can adjust the "hairiness" (is that a word?) to taste using the Bias adjustment. Just like a real amp, the hotter you bias it the less hair and the rounder the sound. Eddie purportedly ran his bias somewhat cold to give more hair on the notes. All the Class-AB amps default to 0.35 bias which is "optimum" for a push-pull power amp. Don't be afraid to play with this value.

The whole thing that "modern" amps do is they simply add bass and treble boost via the power amp feedback network. It's just a slightly more advanced version of the classic presence circuit which is only treble boost. By adding bass in the power amp they can use less bass in the preamp increasing note definition. If you increase the Damping you exaggerate the mid-scoop since the amount of boost is a function of the Damping. The Depth control adjusts the amount of bass boost and the Presence the amount of treble boost. Crank them both up a bit for that modern mid-scooped sound.