Good Tube Selection for Atma Sphere S30?

If I'm guessing the correct manufacturer it's too bad the curves of the glass envelope of those tubes aren't more reminiscent of the famous Italian actress. They'd be a lot sexier.

Thanks, Ralph. Excellent info.

What prompted my question is that I am using a matched quad of a highly regarded and expensive current manufacture 6SN7, of Chinese (not Russian) origin, which in some sections of some of the tubes measure as low as 3 or 4 megohms. I won't mention the name, but it is reminiscent of a famous Italian actress :-)

That results in a very slight hum with my VAC amp and 97db speakers. The tubes sound wonderful otherwise, btw. Some vintage CBS tubes I have, which sound poor in comparison, have no measurable leakage and do not produce any hum.

Thanks again. Best regards,
-- Al

I'm putting my Sylvanias back in:)

Hello Al, We reject the tube if we see less than about 10M. On some speakers its not such a big deal, but if the amp is used on horns tubes with such leakage are trouble makers.

Its not really that hard to find tubes without leakage (+50 Mohms) if you stay away from the Russians (BTW we *have* seen vintage Russian tubes that work great). So far IME if the tube tests with leakage, that is not going to change over time.

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

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I recently tried a newer version of the S30(I used to own the original version)and it had great bass impact on my Ref 3A Grand Veena speakers.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

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

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

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.

Clio,

I was using a Cary SLP-05 ( a left over from the 805AE monos I sold). I found a used Atmasphere MP3 here on the Gon and I am using that full time. Enhances the accuracy and realism of the S. I liken it to a fine dry wine, full of flavor but not overly sweet or lush; clean without solid state edginess

Jimothya,

Great link to 6SN7 information! Thank you

Ralph, on your site you say that "more recently we have seen similar problems in reissue tubes marked "Tung Sol" and "Mullard". What kinds of problems? Who makes the 6sn7s you have for sale?

Each A-S amp has one or two 6SN7 positions with the largest impact on its sonics; those positions vary by amp and vintage - email A-S or check the OTL forum on the Asylum to locate this/these on your amp. You will get the biggest dividends there and the differences are not subtle, at least on acoustic music. Of course other positions also affect sound, just not as much. There is, imo, no modern 6SN7 the sonic equal of a quality quiet NOS valve in A-S gear. Agree with Pubul57 about Andy at Vintage Tube Services - he takes his time but excellent product - best to call rather than write.

Here is a good place to start.

My NOS favorites:
1. Sylvania VT231 & 6SN7GT (especially the '52 green label w/ 3 holes in each plate)
2. Ken-Rad VT231 & 6SN7GT
3. RCA VT231 grey glass
4. Raytheon VT231

The current Shuguang CV181-Z Treasure are ok but also pricey - I found them soft in the bass compared to any of the NOS above. The Electro Harmonix 6SN7 are ok: slightly soft and warm, kinda like a Sylvania GTB, but the latter will last longer and its easier find quiet tubes. The modern standard Shuguang 6SN7GTs (not Treasure) that come stock with the amp are consistent, reliable and quiet, but sound rather mechanical to my ears when compared to NOS, and do not last as long. Stick with the stock Russian 6AS7.

Erfranke, what preamp are you using with your S-30?

Sibelius you are sooo right. The S30 does sound very nice out of the box. Thanks for the tip on the front row tubes. I understand now the critical tube locations to try. I had some microphonic feedback which was interrupted by tapping one of the front row tubes ever so lightly. I am going to keep GTBs or later in the back row. Nice to have an amp where you are not thinking in the back of your mind "it could be better if only the tubes were........."

Agree with several of your other posters. No need to change the 6AS7 output tubes. Play around with NOS 6SN7's in the first row first. To be honest I've noticed less of a difference with tube swapping in my S30 than most of my other amps. I'm not saying there is not a difference - it's just more subtle. Don't expect night and day difference. The S30 really does sound very nice out of the box.

The Tung-Sol 6SN7GTB Reissues are considered to be among the best current production 6sn7s - you can get them for about $20 each.

Thank you. Great information

I was on Sophia Electric's website and saw they carry 6SN7's for $100 apiece. That seems pretty steep and I don't know of anyone that has used them. Just mentioning another source for you.

Russian power tubes are fine! The only Russian 6SN7s worth looking into are vintage made in or before the 1960s.

I think Ralph would say don't mess aroung with the 6AS7s - though I did buy the Russian versions from The Tube Store.

Bose tubes, the best on the planet.

Appreciate your responses

I don't mess with the 6AS7's, I use the stock ones that came with the amp. As for 6SN7 tubes I use Raytheon VT-231 in the front row (Ralph mentioned this would be the best spot to try NOS tubes) and Sylvania 6SN7 GTB in the back row. I removed the middle row and use the shorting plugs supplied by Ralph to lower the gain of the amp. Otherwise I just use the stock Chinese tubes in that row.

Love the Black Treasure 6SN7s. Haven't played around with the 6AS7s yet.

Some say it is good to mix RCA with Sylvania - that is what I do - seems to sound good. If you do buy NOS, Brent Jessie and Andy at Vintage Tube Services are consider to be among the best at that sort of thing. What does Ralph say? He might be happy with the Chinese tubes. The best new stock I have tried are the Tungsol reissues; Jim McShane sells them and has a good reputation for matching - though I'm not sure that is particularly important with the amps.

I like the most expensive that Brent Jessie haS,CHEERS,jAMES