This power amplifier was built by Lance Cochrane in California who is known for his scratch amps using modest parts but really good sound. It was used in my system for the past year without issues. I purchased it directly from Lance.
I will try to provide a technical description of the amplifier based on my own understanding and conversations with Lance. It is a pushpull 6550/KT88 amp with 50 watts delivered a side. The input tube is a 6SN7, the voltage gain for the two output sections is provided by a 12AU7 (this is the most important tube in the circuit) and then phase is split by one 6CG7 per channel. Finally a pair of 6550 makes up the push-pull output section for each channel.
The transformers are all harvested from vintage electronics and are seriously beefy on this unit. The mains transformer is unique with three output windings, so in this case a separate B+ was provided through a 5U4G rectifier for the left and right output sections. There is also a separate B+ via a 6CA4 rectifier for the small signal tubes. There is no risk of voltage sag during large transient peaks as a result.
This is a really stable amplifier. The outputs are cathode biased automatically. There are no adjustments to make when swapping tubes. I have never had noise or hum with this amplifier and I felt content to leave it on for longer periods of time. All tubes pictured are included, with a fresh healthy quad of GE6550A output tubes.
I think this amp can run just about anything. It cost me a lot more than my asking price. I am only selling because I got much more efficient speakers. I will acquire one of Lance's lower powered units to play with.
Thanks for looking. Can ship at buyer's expense, I pack well. Please message me any questions.