So at idle, my amp is working perfectly and sounds wonderful.įrom reading discussions about the thermal requirements of the power MOSFET ( ), I know that at a 1/2 turn of the dual ganged pot I should be at ~ 1/2 max B+ and 1/2 max plate current resulting in 1/4 power output. When I have the dual ganged pot set to max B+ (VVR 'off'), my idle values using a pair of standard 6L6 tubes are the following: (Plate Voltage: 445 VDC, Bias Voltage: -58 VDC, Plate Current : 28 mA -> Plate Dissipation ~ 12.5 W or ~ 60% max plate dissipation of 20 W). Here is a schematic of what I believe the circuit to be: I've seen multiple discussions on the cathode biased version of the circuit, which typically devolve into arguments about the cost of the NTE transistors, but nothing regarding problems with the fixed bias version. As such, I cribbed the circuit from an image of the unpopulated PCB from a now defunct installation manual (/attachments/28470d1397674879-vvr2.pdf). I was going to buy a pre-made PCB, but they are no longer produced. One of those dreams was to install a VVR to reduce power output and allow power tube saturation at low volumes. Over the summer I took it upon myself to build my own 5F6-A style amp of my dreams. This is my first ever forum post anywhere, so forgive me if this is not the correct place for this question.ĭespite no real education in electronics, I have tinkered around with tube amps for some time and have a general idea about how they function.

Variable bias vs fixed bias guitar amp