New Russian "Tungsol" brand KT66

[David Root]

Just saw these on Vacuum Tube Valley's website. Anyone try them yet? If they are as good as this brand's 5881, 6550 and 12AX7, they will be 98% as good as NOS Genalex KT66s, currently at $375/pair.

[mhuss]

They look like one of the Russian KT88s but with smaller plates. I'd like to hear them as well, as the KT66 is one of my favorite tubes. ($70/pr at tube depot).



--mark

[dragonbat13]

I put a pair in my twin reverb. I have a pair of vintage 30's @ 8ohms in the amp. I can't compare them to genelex since I haven't heard a pair before. They have a metal base on them that is too big for the springs. It flattens them out. Also the left tube is just about touching the transformer. I plan on keeping them in and only use two tubes so I may move the sockets around for clearence. Anyway the amp has alot of headroom and Punch with these tubes and these speakers. I ran tungsol 5881 tubes before and the KT66's just seem to be sweeter to me. I have only had them for two weeks so I can't comment on them for durablity although they look well built to me.

[mhuss]

The GEC originals and Chinese copies don't have the metal 6550-style base, but they all are tall and fat relative to a garden-variety 6L6GC. I had to move my OT back a smidgen from the stock location when I built my smallbox to leave room for these.

--mark

[Chris333]

I've tried both the Tungsol re-issue and Valve Art KT-66s. I like 'em both better than any of the 6L6s/5881s I have lying around, but they're mostly Sovteks, nothing special. I read somewhere that the Tungsols aren't real kinkless tetrodes, just 6L6s in big bottles, and I have no idea if that's true or not, but I like the way they sound.

They bias similar to 6L6s, whereas the Valve Arts require a bit more bias voltage. When I first popped in the Valve Arts in place of the Tungsols, assuming they would at least be close, bias-wise, I was surprised to see orange spots on the plates. So I shut down, plugged in the meter like I should have in the first place, cranked the bias voltage as high as it would go, and still they were idling at 80mA. Jeezis. After changing a resistor, I could run both brands back to back to compare, but the Tungsols idled at 39mA (minimum voltage setting, -47V), and the Valve Arts at 50mA (max bias voltage, -54V and -57V, not a very well matched set). When I put the Tungsols back in and checked the bias, using the same setting that had the Valve Arts idling at 50mA, the Tungsols were at around 13mA! Maybe the Valve Arts were just a goofy set, but idling at 50mA, they sound great. I'll have to swap out resistor again and try the Tungsols a little hotter, but they still sound excellent. The Valve Arts have a little clearer low-end idling 11mA hotter, but I'm guessing that's to be expected. The amp is an ODS-clone, and I never push it into any serious output tube distortion.