Home Built 6L6 SE Amplifier

This is a home built 6L6 Single Ended tube amplifier.  The output is rated at 10 watts.  It was built from a PC board circuit, a toroid power transformer, Edcor SE output transformers and a Hammond chassis and cage.  The sound is remarkably good and there is minimal hum and noise at the speakers when you put your ear up the the speaker.

The amplifier drives Cerwin Vega E-310 floor speakers.  The sensitivity of these speakers is 95dB.  The preamplifier is a home built unit with a tube buffer with unity gain that is connected to the power amplifier.  A Logitech Transporter is connected to the preamplifier and I will be adding a RIAA phono peamp soon so I can play my record collection.

I am amazed how good 10 watts of tube amplification sounds.  It is plenty powerful and has that rich tube sound.

This was an incredibly fun and rewarding project.

Update: I changed the Chinese 6L6 tubes to JJ 6L6GC and the Chinese 12AX7B tubes to EH 12AX7 tubes.  I changed the amplifier to Ultra-Linear operation by connecting the Ultra-Linear tap on the Edcor output transformers, changed the toroid power transformer for an Edcor power transformer, and added an Edcor 10H choke.  With the addition of the choke, I hear absolutely zero hum in the speakers with my ear at the speaker.

It seems that a toroid transformer can pass some line noise through to an amplifier.  I was using some power line networking adapters for the Logitech Transporter that were generating noise that the toroid transformer passed through.  Needless to say the power line network adapters are gone and I hard wired the Logitech Transporter to the LAN instead of using the power line adapters.

I’ve learned that the key to low hum and noise in a tube amplifier is a good grounding scheme (not as simple as it sounds), a power supply choke, and proper filtering.

 6L6 SE Amplifier Specifications

• Power Output 10 watts per channel.
• Ultra-Linear operation.
• 23 dB voltage gain.
• Power Gain 200.
• Input sensitivity 500 mv.
• Input Inpedance 1M ohm.
• Output Impedance 8 ohms.