In 2004 Stereophile magazine published an article on the WAVAC SH-833-A pair of monoblocks which at the time cost $350,000 a pair. Until I read the reviews of this use of a quart-sized radio station transmitter tube I thought the idea was a joke but in the back of my mind I thought it would be fun to build one. I spent over a year and a half designing it, building it, and testing every way I could think of to choose the best parts and configurations and I think my design has several things about it that are better than the WAVAC SH-833-A. Like the SH-833-A I use just under 1000 Volts on the plate four separate power supplies for plate voltages of all tubes (two one kV for the plates of the 833-A's and two for the directly coupled mu follower 2C22 series input tubes that must use the same power supply to directly couple them to the 45 triodes which are transformer coupled to the grids of the 833-A's) Two highly filtered 10 Volt 10 Amp cathode heater power supplies for the 833-A's using 4.5 farad filter capacitors, center tap AC for the 45's puts no hum in the speakers, and two 6.3 volt transformers to heat each channel for the pairs of 2C22's. The SH-822-A puts a positive bias on the 833-A grid to make it draw more current so it can put out more power. I run my design at zero grid bias to eliminate a power supply from the signal path. I tested it with 18 Volts positive grid causing the 833-A's to draw more plate current. This did not improve the sound and running it at the zero grid bias is more than enough for some very low sensitivity speakers I use with this. I tested this amplifier on a pair of OB7 speakers and my 833-A design sounded better than any bi-amp or try-amp with 45's on the tweeters and midranges and the 833-A's on the woofers I tested.
It took less than $2000 in parts to build the final design after testing several different coupling transformers and capacitor and parallel feeds. I think the 45's are a better sounding tube than the KT-88's the SH-833-A uses and combined with the elimination of the positive grid voltage bias from the signal path I think my design is better than the SH-833-A. I use Hammond air gap output transformers good for 300 ma and isolation of 4000 Volts with the plate current of only 115 ma so these transformers are a good match and Hammond is an underrated transformer.
I would like to sell a kit for anyone who would like to build my design and I am open to advice on the best way to do this, including a fair price I should charge for this and I will consider custom building the all or some of the cabinets for this system. But these individual blocks are heavy and difficult to ship. I would also consider this an advanced project for a kit builder because the 1000 Volt supplies could be dangerous to any who do not know what they are doing. Ideally, I would prefer to have prospective buyers of the kit audition in person my prototype if they are in Delaware so I can more closely work with or for them in building this design. I can be reached at drbarney1@yahoo.com for this purpose. I have posted pictures of my system on Facebook under Barney Vincelette
https://www.facebook.com/Barney-Vincelette-226017954106804/?eid=ARB7EtqTuwZ2VxqHdDW1cXNQ468PqDoPTt51NniNS7ene6Jw4OvxDpjjT3gO2idKj40Ocnw-DaAIpIJv.
I know Danny has sold other amplifiers others have designed and built and I also accept a monster 833-A SET is not for everybody, but I think it sounds more like live concerts and operas in the opera house I go to.
