stand alone power amp

[andrew]

I looked at a Boogie %0watt power amp schematic and there is a 12ax7 before the 12ax7 phase inverter. Why is it there? Could a power amp be built with just the phase inverter 12ax7? Thanks for any help.

[Bear]

Usually it's to act as a buffer and/or make sure there's adequate drive before the PI. If you know that your input will be of the right sort to drive the PI, you could skip it on a DIY. Gotta be ballsy to do it on a commercial product and tell the disappointed customer that it's their fault for using it wrong.