Dr. Z PHD 1x10 Electric Guitar Tube Combo AmpHaving a love of small, single ended class A amps since hearing the opening bends of Joe Walsh and the James Gangs staple Funk 49, a huge tone that was recorded with the tiny 5 watt tweed Champ, Dr. Z followed his ears in his latest offering, the PHD. The attraction to class A, single power tube, single ended amps is in their hallmark of swirling, even order harmonics and the additive play feel you get from pushing a power tube towards its limits,