Tube DIY Asylum: Re: Looking for a GOOD 211 / VT4-C Schematic by Paul Barker

Good start on parts collection.

Just read you other responses and would like to just encourage you. Though the modern Chinease 845 is a good beast plenty of us really like the nos 211 (which is mostly available as vt4c). I wouldn't say it was time to change direction entirely and start again with the 845. Enjoy the 211 project it's a good idea. I see plenty of ideas I wouldn't carry out, this isn't one of them.

Parafeed may be impractical because of the problem finding a suitable cap. Secondly if your OT's are wound for SE they won't do parafeed justice. The parafeed boys maximise inductance of the OPT for best effect.

The 6c45pi circuits are certainly an option, there may be a better way for you. The thing is to start with the curves and determine an operating point for the 211. It is a very valid point someone made about the cost/availability of high voltage caps. Your parameters are min. 10 watts from 2 volts, 10k load, only A1, preference for high voltage.

I'll go and doodle on the 211 curves and come back.

IN brief the circuits available some mentioned here are a 6c45pi to 211 in various forms, the FI Primer style (which includes Ongaku) multiple stage then direct coupled cf driver, which I think we want to try and avoid as it isn't necessary for us. The Sukuma like 211 IT 211 style fo which there is a truly indulgant version in Sound Practices. The Camille version in Sound Practices, this is very complexed and the shunt regulation which is so integral to the design is complexed (requiring a second article). However I rather fancy that to use the valve topology of that design without the shunt regulation may become an option. That is to say a single voltage amp/driver made of parallel 6SN7 (either in srpp or Kimmel MU) maybe direct coupled to your 211. It all depends what power we can achieve from 2v after it's been through the 6sn7 stage. Do you mean 2v peak or rms? Peak would yield about 28v peak drive to the 211. I think that would be enough for at least 10 watts, but I'll have to go away and look at the curves. I'm rusty on them because I'm working with the 212 these days instead so none of this is part of my current mind set.