Audio amplifier with 6SN7 tube.

This is my new design, 6SN7 tube amplifier. 6SN7 is designed under WWII, and used in many highend HIFI amplifiers. This design use mosfets in the output stage. The price is very low, and the performance and sound quality is very high.

The amplifier is building on 5 separate copper and aluminium sheets.
2 mm copper sheets are used for the mosfets, and 2 mm aluminium are used for the power supply and tube amplifier sections.

Here we can see the mosfet power and the tube power transformer.

Here are the two 6SN7. One tube for each channel.

Here is the schematic for the tube power section, mosfet power section and one of the two amplifier channels.
Each tube sections are set to maximum amplification by the 100 uF cathode capacitor.
Input signal is connected through the 10 K log potentiometer to the 47 K grid resistor. A feedback signal is taken from the anode through a 270 K resistor. The amplification is set by the input resistor and the feedback resistor.
Stage two have the same connection, except for the input resistor is 68K, and the feedback is taken from the speaker output. The mosfet output stage is also mine idea and design. The 10 K pot set the current in the mosfets. The current cause a temperature raise in the mosfet heat sink. The current is set to a temperature on the heat sink of about 30 C.