6080 mil spec (same tube), should have better element support structures inside, and maybe even thicker glass, could also feel heavier. Which all should make it less microphonic and far sturdier, as for sound difference compared to 6as7g try it and see.
For memory I had them from input 13D3 > as pre drivers >to the 300b> interstage trany > 805 SET monoblocks I had, real massive hot beast of amps
Cheers George
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What George above said and / or try asking Ralph at Atmasphere himself. He writes here from time to time.
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I know that old stock 6AS7Gs dont typically work as well in place of the newer types that Ralph sells. The same may be true of 6080s.
My advice would be to concentrate on the 6SN7s and to leave the power tubes alone at least for now. Not all sections are equal in terms of sonic impact and it may be that you need a pair of GTA or GTB in one section with GTs/5692s being acceptable elsewhere. Call Ralph and he will clear this up.
I have retubed Atma-spheres before and my clients have reported positive results using old stock 6SN7s. I have never replaced any power tubes. Mixing 6SN7 pairs with different strengths seems to yield positive results. |
@drbond
My advice is to stay away from the 6080s on these amps! They are not built to the same spec as 6AS7Gs. The 6080 typically has a smaller grid heatsink and since the amp is biased in class A2, the grid can warp at higher power levels, causing the tube to arc- and often taking out multiple tubes at the same time. This won't damage the amp or speaker, but it can result in the user getting gun-shy and thinking there's something wrong with the amp when there isn't! Some people claim to have had good luck with 6080s but IME they've told me that while dealing in the same breath with failing tubes.
This advice extends to the 6AS7GA as well as any other variants. Stick to the 6AS7G. Now when dealing with American versions, if the tubes are NOS they will need to be preconditioned for *at least* 4 days and 4 nights in order to have any reliability. Otherwise the cathode coatings flake off and cause the tube to arc and fail. Of all the vintage types the Sylvania made examples hold up the best (and not surprisingly are the hardest to find).
So the Russian '6H13C' is the most reliable IME. If you use the Chinese 6N13 make sure its a military example such as seen with the 'PJ' suffix. The Chinese tube can develop what looks like a smoke ring on the inside of the glass; if you see this discard the tube (because the tube is failing and might arc). The Russian tube does not do that.
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always nice to hear advice from the actual maker of nice gear... |
@atmasphere:
Thank you for your detailed response!
Have your customers mentioned to you what changing out the stock 6AS7G tubes for either the Russian 6H13C or the Chinese (I assume ShuGuang) tubes do differently, for better or worse?
Would you suggest just rolling the 6SN7 driver tubes for more adjustability?
Thanks.
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I've had my MP-1 and M60s for 20 years now. Follow Ralph's advice and stick with the Russian provenance 6AS7Gs or, alternatively, the 6H13C. I had a brief fling with the Chinese variant and found they had a high failure rate/short life span. |
IME, it was problematic to roll the 6AS7 output tubes in my M-60.
I have always been a fan of NOS,
I got a set of 6AS7Gs from Brent Jesse.
They we’re not matched and were three different brands as Brent said.
As Ralph said, the failure rate of NOS is high compared to the stock Russian. 3 of the 16 failed. However, when I got good ones in, the power output went up about 20% and the tone was much better.
I would highly recommend going with NOS as long as you are aware of the failure rate, |
Have your customers mentioned to you what changing out the stock 6AS7G
tubes for either the Russian 6H13C or the Chinese (I assume ShuGuang)
tubes do differently, for better or worse? Actually the stock tubes **are** either the Russian or Chinese tube (which seem to sound the same; the difference is in how they fail). Would you suggest just rolling the 6SN7 driver tubes for more adjustability?
People roll the 6SN7s all the time with nice results. We've found that that Sophia tubes while sounding great at first, seem to have a short life of maybe only 6 months, whereas a regular NOS tube in the same spot can go for years. The one tricky bit is the driver tube which in the MA-1 will be in a different location depending on when the MA-1 was built. If you have a version with reflected left and right hand chassis the driver tube is on the corner facing the power tubes; if a newer chassis the driver tube is the one in the front. This particular tube must have a -GTA or -GTB suffix if you're using an NOS type. Modern 6SN7s like the Shugang 6SN7 or Sovtek are marked 'GT' but are actually GTBs. If you are forced to use Russian made 6SN7s (which conversely and confusingly from the Russian power tubes are usually a poor choice), they should be screened on a tube tester to show no leakage at all on the leakage test, otherwise you may encounter a buzz. The lifespan of these tubes is also really variable going anywhere from 2 weeks (in which case send it back to where you got it and get it replaced; most tube sellers have a 90 day warranty) to maybe 2 years. |
i too have wondered why russian power tubes are very good (i use el34 and kt88 variants), yet the sound of russian low level tubes like 6922 6sl7/sn7 are rather poor (lacking midrange bloom) and russian rectifiers like gz34's are abysmal in quality and lifespan
ralph, any theories or thoughts as to why this is the case? |
@atmasphere
Thank you for the reply.
In my estimation, your direct contact with the people who use your products, and your willingness to share your time and expertise, shows that you really enjoy what you do, and your products reflect that.
I rolled out the non-driver Chinese 6SN7's, and placed Tung Sol NOS 6SN7GTB in their stead, and the sound stage and detail really materialized right in front of me.
I'm planning on trying Ken-Rad VT231's and CBS Hytron 5692's in the primary positions of the 6SN7's closest to the back of the MA-1 mark 3.3 next. But it sounds like I should stay away from Russian 6SN7's, which would include National, and some modern Tung Sol from Russia?
I was considering trying out other power tubes (like possibly the 7236), but given your advice, I think I'll just stick to the Russian 6H13C.
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ralph, any theories or thoughts as to why this is the case? We suspect that the environmental control is poor- tubes are made by hand and we've heard that they don't use Latex gloves in their assembly. That comes from Eric Barbour back when he was involved with the US Svetlana brand and so may well be completely inaccurate at this point but we see the same problems now that we saw 20 years go when he was there. That's my best guess as this would affect small signal tubes more. A pragmatic individual will simply roll with the punches... But it sounds like I should stay away from Russian 6SN7's, which would include National, and some modern Tung Sol from Russia? I can't speak to the National brand- some of that might be production prior to the fall of the Soviet empire and might actually be OK (Russian 6SN7s from the 1960s can be excellent, but pricey and the differences in appearance from the current Sovtek junk is subtle so buyer beware). But IMO the EH, Mullard or TungSol (which are all nearly the same thing) don't hold up to the (advertising) hype. FWIW though we have seen some of the Gold Lion branded 12AU7s out of Russia be quite good. |
For those who are interested, here is the link to another site, where tube rolling the 6SN7 voltage gain / driver tubes is discussed, as well as Ralph's input:
Atma-Sphere MA-2 Amplifier | What's Best Audio and Video Forum. The Best High End Audio Forum on the planet! (whatsbestforum.com)
Doc nowack said:I’m roiling tubes to fleshout the lower mids and bass. I would be interested in hearing from others concerning there experience with tubes and placement in the amps.
The four tubes in the rear are the voltage amplifier tubes- the two 6SN7s closest to the front panel are the driver tubes.
So the driver tubes, if you want to try rolling, should have -GTA or -GTB suffixes as they are subjected to higher voltages which will shorten the life of a GT.
The voltage amplifier tubes are the most important to the sound of the amp. The voltage amplifier is where all the gain of the amp occurs. It is a differential cascode circuit aided by a constant current source, resulting in fairly high CMRR (Common Mode Rejection Ratio) over 100dB.
There are three 6SN7s in a differential and parallel arrangement which drive the cathodes of the 4th 6SN7 which is the top of the differential cascode. So those first three tubes have the most sonic impact. Yyou don't have to replace all three when auditioning a tube brand (although the cumulative effects will be easier to hear if you replace all three). The top of the cascode IOW has less effect on the overall sound than the bottom, so you replace the first three 6SN7s from the rear panel first, then the 4th.
We've got very good reports of the Psvane and TJ Music 6SN7 variants. Note that they should not be used in the 5th and 6th locations as they don't have the additional voltage rating of the -GTA and -GTB suffix. People report that these tubes have all the best character of the best NOS tubes (Ken Rad being the best, followed by the metal base chrome dome Sylvania after that probably the RCA red base or CBS Zalytron)) without any of the weaknesses! Pretty powerful statements IME.
On tip: have fun- don't drive yourself crazy. I go for a good musical presentation; if I'm getting that I spend the rest of the vintage tube money on more LPs
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One more troubleshooting note: I had an awful buzzing/loud humming coming out of one of my Sound Lab speakers. I switched MA-1 monoblocks, and the buzzing switched to the other speaker. Then I proceeded to replace all the output tubes, first seven on one side, then seven on the other, and tested after each replacement. The buzzing was still there. Next, I proceeded to replace the most posterior (sonically important) driver/gain 6SN7 tubes, but the buzzing was still there. Lastly (almost) I replaced the main driver tube, which is in front in the Mk 3.3 model, and the buzzing immediately stopped. I was most surprised that this was the failed tube, as it was a new tube, with less than 30 hours on it, and it was a modern Tung Sol 6SN7 GTB. . . so it appears that currently Ralph’s suggestion to stay away from the Russian 6SN7’s seems to be rather accurate. |
I was most surprised that this was the failed tube, as it was a new
tube, with less than 30 hours on it, and it was a modern Tung Sol 6SN7
GTB. . . so it appears that currently Ralph’s suggestion to stay away
from the Russian 6SN7’s seems to be rather accurate. If you look on our website you'll find this warning, which has been there for nearly 20 years now NOTE REGARDING SOME TUBES
We
have seen on-going problems with 6SN7s marked as "Sovtek" and "Electro
Harmonics" More recently we have seen similar problems in reissue tubes
marked "Tung Sol" and "Mullard". We do not recommend these tubes in our
products. While they will not damage our products, neither will they
perform optimally or reliably. If you are experiencing a problem and any
of these tubes are installed, replace them first before doing anything
else. |
@atmasphere:
Thanks for the reply. I must admit, I haven't read much of your website, but only the instruction manual that came with the MA-1.
The amplifiers are a phenomenal match for the Sound Labs. I'm enjoying them immensely. Thanks for your great work!
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Hello Ralph (@atmasphere),I'm posting this here so others can share your response; apologies if there is a more appropriate place to ask.I just bought a pair of M-60s, built as II.2s but upgraded by you in 2008 with a PS boost; they have just one switch and one pot on the front. I cannot get the output to null on either unit, so I am wondering how to proceed. I checked all output tubes for blown tiny fusible links near the base, and indeed found one ( but only one ) bad tube. Even if I remove a tube from the other side of that unit, output will still not zero. On both units, I have to turn the pot fully CCW to get a minimum. On one unit it's down pretty close to zero, on the other one closer to mid-scale.So: 1) is it safe to run the amps unbalanced, at least for a little while?2) without a tube tester, how do you suggest I find bad tubes? For example, could I start with just one tube on each side and juggle tubes until I get a balance, then try for 2 on each side, etc?Thanks!
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@crowdaddy2
Insofar as I know, the best way to find a failed tube is trial and error: you should have a second full set on hand anyways. If replacing all the tubes doesn't work, send back to manufacturer for check-up. Ralph and Atma-Sphere will be glad to evaluate the problem. I don't think anyone can really tell you what the problem is without physically evaluating the unit.
Best wishes!
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I swapped tubes between sides until I got a good null on each unit. As advertised, the M-60s do sound great: most noticeable immediately was better localization of sound sources. Will take a gamble on some $20-a-pair jugs from Ukraine; perhaps if I precondition them they will last a while. Am thinking of building a uTracer: https://www.dos4ever.com/uTracer3/uTracer3_pag0.htmlVery clever tube curve tracer, over 1800 built so far. |
I had good luck with Ken-Rad VT231's in my MA1s. Cheers,
Spencer |
