Single-Ended (SE) 6550 Tube Amplifier Schematic
SE 6550 Tube Amplifier Schematic with 12DW7 Driver Stage
This single-Ended (SE) 6550 design is based on a minimonitor constructed by Lars Ohlsson of ElektroAkustik & Music.
Single-Ended 6550 Tube Amp Schematic with 12DW7 Driver Stage
The single-ended amplifier circuit uses a 6550 high power tetrode vacuum tube in the output stage. A 12DW7 or 7247 is used to drive the output stage. The 12DW7 / 7247 is a dual section triode, the first section has a gain factor of 20 and the second section a gain of 100. You can think of it as one-half of a 12AX7 and one-half of a 12AU7 in the same envelope. New production JJ ECC832 tubes are a suitable replacement for the 12DW7 and 7247 which are no longer in production. C2 and C3 should be good quality film capacitors. The cathode bypass capacitors C1 and C4 will also have some impact on the sound and good quality low ESR capacitors are suggested.
Output power will be about 7W. With the 390 ohm cathode resistor (R9) the 6550 draws 91mA which is about 82% of the maximum plate dissipation. A 330 ohm cathode resistor (5W) will increase the current to 103mA which is about 92% of the maximum plate dissipation. The audio output transformer should be 3k and rated for at least 10W.
Power Supply Schematic - Single-Ended 6550 Tube Amp
The transformer ratings shown in the schematic are minimums. A linear power supply using bridge rectifiers is used for the Single-Ended 6550 Tube Amplifier. Adjust the value of R11 to get 400V. To improve the power supply a 5 to 10H choke can be used in place of R11. Pick choke with a similar resistance as R11 and rated for at least 500VDC and 125mA. A film capacitor is preferred for C9.
Power Supply Schematic - SE 6550 Tube Amplifier
DIY Single-Ended 6550 Tube Amp (Monoblock)
One of the finished Single-Ended 6550 Tube Monoblock Amplifiers with a Sovtek 6550WE.
DIY Single-Ended 6550 Tube Monoblock Amplifier
I took the amplifiers to the shore and took some photos with the lake, the sky and summer from their very best side.
Back - DIY Single-Ended 6550 Tube Monoblock Amplifier
Bottom - DIY Single-Ended 6550 Tube Monoblock Amplifier
Underside - DIY Single-Ended 6550 Tube Monoblock Amplifier
More Single-Ended 6550 / KT88 Tube Amplifiers
- SE KT88 Tube Amplifier Schematic (6N1P driver) by Mikael Abdellah
- SE KT88 Tube Amplifier Schematic (12AX7 driver) by Jean Hiraga
- SE KT88 / 6L6 / EL34 / 6CA7 Tube Amplifier Project (6N1P driver) by Alex Gendrano
- SE KT88 Tube Amplifier thread by Bernardo