6N3C Russian Tubes in VTA-70

Folks,

I did some searching around the Internet and have not found whether it is safe/possible to use a 6N3C in a VTA-70. (Without the PT/OT upgraded.) I ran some 6N3Cs and they were fine but one of the tubes started to red plate. I purchased some new ones and whammo, two of the tubes red plated. To make sure that I didn't screw up the bias resistors and the caps, I always made sure that the amp was immediately turned off. When I go back to standard EL34s or KT66, no red plate and the bias is fine and the amp loves it. I'm thinking it might be these tubes.

1. Can they be used in the VTA-70?
2. Has anyone run them?

Thanks,

FG.

I have a matched quad of Soviet-era 6N3Cs (better known as 6P3S in the West) that I ran for several months in my VTA ST-70. The 6P3S is a cousin to the 6L6GC or 5881. A matched quad can usually be purchased for under $50 USD. I got my set from Cryoset. They biased up perfectly at .4v at the 12 o'clock position on all four bias pots.

I never had a problem with red-plating or anything else. I simply preferred the sound of other power tubes, specifically, the Shuguang KT-88 or EL-34.

I generally prefer the sound of Chinese power tubes and NOS driver tubes, but I have not tried all the hundreds of combinations possible. Russian power tubes sound (to me) kind of dry, accurate, and literal. Chinese have kind of a rosy glow, but it's all about mixing and matching.

If your 6P3S power tubes are red-plating. they are probably defective.

Gregg R. wrote:I have a matched quad of Soviet-era 6N3Cs (better known as 6P3S in the West) that I ran for several months in my VTA ST-70. The 6P3S is a cousin to the 6L6GC or 5881. A matched quad can usually be purchased for under $50 USD. I got my set from Cryoset. They biased up perfectly at .4v at the 12 o'clock position on all four bias pots.

I never had a problem with red-plating or anything else. I simply preferred the sound of other power tubes, specifically, the Shuguang KT-88 or EL-34.

I generally prefer the sound of Chinese power tubes and NOS driver tubes, but I have not tried all the hundreds of combinations possible. Russian power tubes sound (to me) kind of dry, accurate, and literal. Chinese have kind of a rosy glow, but it's all about mixing and matching.

If your 6P3S power tubes are red-plating. they are probably defective.

I bought a lot of them recently from someone I've purchased from in the past. It seems that three of them are bad, three of them are good. And I have more. These last four that I tried sounded great, biased up to .40 and then one of them showed a SLIGHT red plate on the seam. All of them are on the seam of the plate. It's weird.

Thanks again for your thoughts, I appreciate it.

FG

I have the Russan 6P3S with about 600 hours on them, I think they draw a bit more current than others, as the VTA board bias pots get cranked a bit more clockwise to settle them in at .40 bias voltage as compared to the EH6CA7 or new issue Mullard EL34's I tube swap on my ST70.   I did have a bad 6P3S in the initial quad when I first purchased the was replaced by the supplier, no issues after that.

Make sure when you buy these nos tubes to get the 6N3C-E . I bought a quad from Cryoset
and I think they sound great. I have these biased at .47 I get better bass with the higher voltage.