Hybrid amp using a paralled 5687 tube and Magnatec PowerMosFets

Amplifier specifications :

- driver stage uses a paralleled 5687 tube.
- power stage uses Magnatec PowerMosFets, the BUZ900P and BUZ905P.
- no feedback.
- high voltage powersupply uses Philips 058/059 Series capacitors.
- low voltage powersupply uses BH SlitFoil capacitors.
- low and high voltage supply uses ultra fast soft recovery diodes - coupling caps are made by SCR (ChateauRoux/Solen).
- THD + N is 0.64 % and -68 dB at 1 watt. Distorsion is mainly 2nd harmonics.
- damping factor 5.3.
- output power 50 watt into 8 ohm.

Comment to this high voltage supply : capacitor C2 and C3 should be increased to 470 uF, this to avoid hum. Other option is to add an extra RC combination (60 ohm and 100 uF) or replace R2 and R3 by a choke. I'm using a 6H - 60 mA choke in each section. I choose for R1 180 ohm.