GoodSoundClub - Romy the Cat's Audio Site

In the Forum: Melquiades Amplifier
In the Thread: A different breed of 6C33C amplifier.

Post Subject: It's the tubePosted by KOTriode on: 9/18/2011

Romy,
I have good confidence that it was the tubes and not the circuit. I have checked the cathode driver that bias the 6C33C and there was not any problem. Sure if the cathode bias failed, the 6C33C current will shoot way up and burned up the fuse, it did not happen in this case. The 6C33C tube went with a small pop, such as you cue the cartridge onto a record, it did not die, but the bias current is way low. I have a total of 8 tubes, after burning in the heater for a day and test the rest of the tubes, now I have only 4 that bias is within 10V of each other. The other 3 is about 30V off, and one did not have conitnuity on 1 filament. Like you said, I probably bought some garbage tubes.

I just order some 6C33C tubes on Ebay: [Edited: link removed.]
because these looked interesting with gold grid wire, none of my 8 tubes I had it. I will test these as soon as I receive them.So far nothing was damaged except the tubes, that is good news. I remember reading somewhere that other tubes like 6AS7 sometimes short the plates, one time at the show, I was listening to an OTL that has about a dozen of these 6AS7 tubes, and one of them sparked with a flash and make a very loud noise on the speaker, I hope the same thing does not happen with the 6C33C in the future.

Anybody out there felt that there is one brand of 6C33C better than other? What about the Svetlana?

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