Sovtek 6SL7

[Mick Bailey]

A few weeks ago I bought a Sovtek 6SL7 and it was a nice surprise that it was a rebranded 6H9C from 1974. A trial in my recently-acquired Reverberocket in V1 position proved it to be a really good tube with low microphonics and a little less noise than a NOS Sylvania. As follow-up I bought another four tubes, this time the originally designated 6H9C in original Russian boxes. These are every bit as good and the spec sheet with them gives identical parameters to the 6SL7. Those are dated 1982 and the yellow boxes say 'Radio' in Cyrillic. They're identical to the Sovtek tube and I'm really happy with them. They're also inexpensive.

On the way is some Russian equivalent 6SN7 to see how those work out.

[Pedro Vecino]

As with 6SC7 and 6SN7, there are two Russian models: the old one and a more modern one.
It is possible that the modern ones correspond better to the original specifications of those tubes and the old ones are "the Russian equivalent" (sometimes more similar and others less similar).
In both cases, the old ones are well distinguished by their particular disposition of the micas.

[Mick Bailey]

I got two Russian 6SN7 yesterday - one was OK, though slightly more microphonic than I'd like, but usable. The other totally unusable - very low gain and excessively microphonic. I could tell it was going to be bad because it rattled when I removed it from the box and it's worse than ones I usually chuck out. This also highlights returning parts to Ukraine from the UK; the return postage is more than the combined cost of tubes plus postage from Ukraine.