Good Tube Selection for Atma Sphere S30?

Pubul57, there are now Russian made, newly manufactured tubes marked 'Tung Sol' and 'Mullard" as the US importer has acquired the rights to those names here in the US.

What we have been finding with these tubes is very similar to what we find with the Electro Harmonix brand, as well as the generic Sovtek; if you put the tube on a tester it seems very likely that it will show leakage on the leakage test of the tube tester.

In practice, tubes with leakage can buzz if used in our amps. An additional issue has been that the life expectancy of these tubes seem to us to be really variable, some lasting only a few weeks. OTOH, we've seen US and Chinese tubes go over 50,000 hours.

I did inform the importer about these problems a good ten years ago. I was told that the 'next batch' would be different but so far that has not manifested, as far as I can tell.

Atmasphere, does this apply to the 6AS7s as well? You'd said above that power tubes from Russia were fine...

That's correct. The 6SN7 is the tube where we've seen problems. The Russian power tubes work just fine :)

I used Brimars and they were an improvement.
I also had the MP3, it was a great combination,I was using stacked Quad 57's at the time.

No problems with the stock output tubes.

I recently tried a newer version of the S30(I used to own the original version)and it had great bass impact on my Ref 3A Grand Veena speakers.

The S30 is the one amp I wouldn't hesitate revisiting.

12-14-11: Atmasphere
In practice, tubes with leakage can buzz ...

Ralph, assuming you are referring to heater-to-cathode leakage, how many megohms of leakage resistance would you consider to be the threshold of acceptability for a 6SN7, as measured say on a vintage Hickok tester?

Also, based on your experience is it expectable that a tube showing marginal leakage (perhaps 2 to 5 megohms, for example) during its early hours of use will improve over time?

Thanks! Best regards,
-- Al