Stereo tube amplifier circuit diagram based on 6SQ7-GT and 6V6-GT

This is a circuit diagram for a stereo tube amplifier using 6SQ7-GT and 6V6-GT. The tube amplifier circuit uses a total of 5 power vacuum tubes. This diagram is based on the output section design of a typical late 1940's vintage AM Trutone radio with 6 valves. Output will be 4 watts per channel (2x4W stereo tube amplifier)

Parts List:

R1A & B = 500K dual potentiometer

R2, R6 = 1M1/2W

R3, R7 = 470K1/2W

R4, R8 = 220K1/2W

R5, R9 = 330, wirewound or metal oxide 2W

R10 = 750, wire wound 20W

C1, C4 = 200pF/600v

C2, C5 = 47nF/600v

C3, C6 = 22uF/25v

C7 = 47uF/450V

C8 = 33nF/450V

C9 = 10nF/1400v

Power transformer, T1

Primary = 117v 60 cycles

Second. 1 = 600v CT @ 80mA

Second. 2 = 5v @ 2A

Second. 3 = 6.3v @ 4A

Audio output transformer T2, T3

Primary (impedance) = 3300 @ 400 cycles

Secondary (impedance) = 4 or 8 @ 400 cycles

Electron tube:

6SQ7-GT

6V6-GT

5Y3-GT – Full Wave Vacuum Rectifier

Things to note about stereo tube amplifiers:

Don't forget about connecting cords, sockets, switches and the case or circuit board. All tubes are octagonal and require an octagonal socket.

For optimal audio reproduction, speakers with 90db/watt or higher efficiency are required.

Shield any connecting wires used in the signal path between the input jack and the first audio tube.

A choke with a DC resistance of approximately 750 ohms can replace R10.

R10 generates a lot of heat and requires attention to its placement. I applied a large adjustable wirewound resistor to this and mounted it above the chassis. The choke in its place will provide better performance and be more similar to the electromagnetic field in the prototype.