Thanks for everyone's comments. Ken, I'm building a pair of single-ended mono amplifiers using the 211 tube. This has been a very long project so far with several dormant periods due to other committments. I've also been delayed due to the difficulty in acquiring quality, non-Asian parts, and prior to purchasing the Taig lathe and mill, I had become stymied by the need for expensive metalwork.
The electrical design is my own, something that evolved over a period of several years. Much of that time was spent in critical listening tests with various driver tubes and topologies. There was also an initial period of basic design work, some of which had to be transferred to the prototype on an empirical (trial and error) basis.
Here's a poor quality photo of the prototype, which I still have:
In a nutshell, the amplifier operates in Class A until it reaches about 15W output, then it moves into A2. In A2, it can produce about 25W. I don't know of any other 211 SET ever built with this capability, and I spent much of the original design time working through the details. The result is an amplifier that operates at "standard" SET power levels, but which can handle musical peaks and brief overloads without audible distortion. I'll add that the amps use separate power supplies for the driver and output circuitry, and that the 211 filament is powered by an ultrasonic AC supply operating at roughly 70 kHz.
About the metalwork, I'll eventually produce something like 100 parts for the pair of amplifiers. Much of the chassis is constructed from 1/4" 6061 plate. The front panels are 1/2" stock. Each amplifier will probably weigh about 70 lbs, much of that being the output and power transformers.
Schematics and advice are freely available to anyone interested. :)
--- In firstname.lastname@example.org, Ken Jenkins <kjenkins@...> wrote:
> Jack this is really beautiful work and that amp is going to be sweet. For those of us with an electronics bent, can you fill in a little detail about the amp itself. What is it? (type, class, power, etc.) Where you get it? or from what plans did you build it? etc, etc. With all that nice work inside on the tube sockets and power transistor heat sinks, you should really go with a clear case so it can be admired! Maybe go nuts and use 1/4 plate glass!!! lol
> Ken Jenkins