6C33-B vs everything else.

Kt 88, I have an alternative suggestion for you to consider: Quicksilver Triode monoblock amps. These fine unadvertised hand made beauties utilize one pair of 6C33's in PP fashion generating a credible 50 watts. Mike Sanders designed and builds these to be his statement product, and succeeds quite nicely IMHO. Darkmoebius described the sonic character of this tube exactly, just like Goldilocks and the three bears, not to sweet, not too lean...just right! With base going down to near DC, and upper frequencies that extend to the clouds there is nothing I don't like about these tubes and these new amps. Consider this long-time EL34 enthusiast a convert to the 6C33!

FWIW, the 6C33C-B is out of production and is not expected to go back into production as the plant that built it is gone- closed about 3 years ago. There is a substantial stock of the tube ('thousands' according to one distributor) still available.

Compared to most power triode tubes the 6C33 has a relatively short service life. The Russian data sheet specifies 750 hours, although in practice you can get up to 2000 hours if all goes well. On account of its filament circuit, the tube runs *very* hot!

Another thing you will want to consider is the socket issue. The socket is a septar type that was originally used by the American tube type 3C33. The Russian 6C33 has considerably higher filament current and the socket was not designed for that sort of service and so has a very short service life.

Anyone who runs a 6C33C-B amp using the Russian socket knows what I am talking about. The contacts begin to fail due to corrosion and weakening of the contact springs. They can be re-tightened, but ultimately the socket has a service life that is in the region of 5000-7000 hours. The American made version of the socket does last longer but is much harder to obtain and is not cheap.

FWIW we made the first American-made products using this tube back in the early 90s. The short service life of the tube and its socket made the tube unattractive.

Hey Badboss429,

I like the look for the Quicksilver Triode. But would like to find one used as my budget wouldn't work for new. I have also found a few other amps that use this tube I'm looking at. I'm in no hurry I geuss. But ultimately I will buy something.

Atmasphere ( with a name like that you must be a OTL guy ) Nice to know about the socket for the 6C33-B. I would be curious if BAT and Quicksilver employ the American version. I'm guessing the cheaper priced amps defintely are not.

I've owned amps from Quicksilver and their quality (both performance and reliability) is fantastic and they are one of the best providers of service in the industry. If you can find one in your price range, I'd explore Badboss429's suggestion.

I owned a Joules Electra amp that utilized the 6c33c tubes. These amps were designed by a true artist who knows his stuff. The tube life within this circuit was quite lengthy. The sockets were without any problem, either in corrosion or contact spring issues. In part, I assume the reliability of these amps and the longevity & freedom from the issues described by Atmasphere is due to the reasonable bias currents utilized within the Joules design.

I had a bud who owned the Atmasphere 6c33c amps and their bias requirements were double what Joule uses. He had a need to replace the sockets about yearly and had constant tube issues.

KT 88, Call Mike Sanders at Quicksilver Audio and ask about tube and socket life. When I inquired, Mike told me that he runs the 6C33 at low stress levels and expects extremely long life out of both (in contrast to other manufacturers that push these tubes hard ex: Tenor and Lamm). Retail is $5800 for the pair, but a nice dealer demo pair could be had for $4200? World class performance for comparatively little money IMO.