I agree completely with Sbank's description of the Atma-Sphere amps. With reasonable care matching speakers, the MA-1 amps are magic.
Jimjoyce25, I own Atma-Sphere MA-2 amps that were very early production MkII amps (mid-90's production). I sent them to Ralph to be updated to MkIII status with the new regulated power supply, new power supply filter capacitors, re-wiring of the output tubes, and a few other changes to bring them to current specifications. The updates should be similar to the update that would apply to your MA-1s. The result of the upgrade was absolutely astonishing in all parameters. Overall resolution improved, tonal purity improved, distortion lowered, bass impact increased materially, and there was a greater sense of "ease" across the spectrum coupled with greater dynamics. My wife and I were extremely pleased with the update; a very very significant upgrade in sound for an amp that we were already extremely pleased with. If you can afford the updates, I recommend you go for it.
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Rleff offers good advice about calling Ralph. He's easy to talk with and will give you straight answers. But, just so there's some response in the thread to your questions...
1. The newest production amps (MkIII) have an automatic self-biasing circuit for the output tubes, so manual bias adjustment is no longer required.
2. A meter is still on the amp, but is now used just for DC offset adjustment, not bias adjustment since that is now automated. (With the manual bias adjustment which I retained on my MA2s, the bias remains dead steady once the tubes have settled in. I check it once a month or so since it's easy to do with the built in meter, but I rarely have to make any adjustment. With the automatic bias adjustment now in the current production amps, this is not an issue.)
3. Changes to the wiring of the output tubes have reduced stress on the tubes making it less likely that a tube will blow it's fuse. (For those not familiar, the AS7G has a built in fuse that simply breaks in lieu of any spectacular display or sound. Thus the need to visually examine the tube for that "small wire" to which Jimjoyce refers.) Ralph continues to recommend a 48 hour burn-in on stand-by of the output tubes for longest life.
It's been three years since I've replaced an output tube, and the majority of my output tubes have been running for more than seven years. One still has to inspect them visually to find a failed tube. I've started using a large magnifying glass to take a look.
4. I use an upgraded power cord, but still find the stock Belkin cords to work pretty well. With the Silent Source power cords I use, I hear more solidity in the bass and a bit cleaner sound through the midrange. But, it's fairly subtle and I could live with the stock cords.
5. With the MA-2 MkIII amps, warm-up is finished in about 45 minutes, about the time it takes for my cartridge to start sounding it's best. I always shut the amps down when I'm finished listening for the evening (and I place them in stand-by when I make an interim stop of 15 minutes or more).
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Hi Tom, good to see your post! One thing folks should be aware of about the A-S amps is that the choice of 6SN7 driver tubes will make a big difference in the sound. In the MA-2s you heard at my house on the standard Eidolon, Tom, we were listening to Sylvania 6SN7-GTA tubes manufactured in the '60s. These have a very clean, detailed and somewhat airy top end. Put in something like RCA grey glass and the top will get much softer and sweeter. Do you know what 6SN7 tubes were being used in the MA-2s you listened to on the Diamonds?
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Tom, it did turn out simply to be break in for the new capacitors installed as part of the update. It took 400 hours for those capacitors to break in, and I was concerned about it. Then one day the amps just clicked over and the magic was back. Ralph was surprised at the amount of break in time, too. (BTW, the update to my amps did not include the new V-Cap coupling capacitors that Ralph has since made standard for the MA-2. All capacitors sound different and I haven't yet heard an A-S amp with the V-Caps. From what I've heard, the V-Caps are exceptionally nuetral and take 400+ hours to break in, sounding pretty brittle until they do break in, but outstanding thereafter.)
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I use Sylvania GTBs with matched pairs in the two postions A-S recommend matching. The straight Sylvania lineup is a good match to my Aesthetix preamp. With a different preamp, some other mix might be better. The Sylvanias were a nice improvement in resolution, openness and timbre to the JAN Philips that I had once upon a time. Life expectancy on these is in multiple years of heavy service.
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Pubul57, I've had the great pleasure recently to spend some time listening to an MP-1 in a friend's system. I'm impressed: very neutral, very resolving and transparent, very quick and detailed. The virtues of the A-S amps in a preamp.
I've not been as similarly impressed with the MP-3 (heard elsewhere), but the MP-1 is a stellar unit that would fall among my top candidates if I were making a change.
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Pubul57, my listening to both the MP-1 and the MP-3 have been as full function preamps playing LPs. You may have it right that my differing reactions come from differences in the respective phono stages, but I suspect that's not all that's going on. I will say that the MP-1 was a vastly more satisfying listening experience for me, getting in the ballpark of what I expect as the result living with the Aesthetix Io Signature with dual power supplies and volume controls. The MP-1 sounds like a great preamp.
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I agree with Pubul57. I used GTAs and was very pleased. When I looked to get more, Andy Bouwman at Vintage Tube Services told me there was very little difference in the sound of the GTBs up through the early '70s manufacture. That's what I'm using now in my MA-2s, and I don't notice a difference. From what I hear in the amps, I wouldn't pay a premium for GTAs over early manufacture GTBs (up to early '70s).
The GTs have a bit of special, but as Pubul57 notes, you can only use them where the high plate voltage capacity of the As and Bs is not required. I need to get a quad to try once again.
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Power conditioning: dedicated 20 amp circuits for each amp, plus an APC PMP2X whole house surge protector panel mounted at the breaker box. Otherwise, no power conditioning. Frankly folks, the MA-1 and MA-2 can draw so much power that the idea of putting anything in between them and a direct connection to the power company is hard to consider. |
Yes, nice review by Sue Kraft. Very complimentary of the M-60 particularly, saying "In my experience, few tube amplifiers have the purity and neutrality of this one."
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