The American 6AS7G and it variants can be problematic due to early arc-over failure. We have had some reports that the tubes hold up better in the MkIIIs and in fact what little testing we have done seems to confirm that. If American tubes are tried in the amp though, it must be regarded as experimental. One recommendation I can make is that the tubes, if NOS, should be preconditioned (tubes placed in amp and run in Standby only) for 72 hours before being used. That seems to reduce arc-over failure with them.
Atma-Sphere MA-1 amps
How good are these amps? I have 200w Class A mono blocks and have been eyeing these for sometime. What are your thought on them and hwo do they sound?
TIA
TIA
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I think the GTAs and GTBs are essentially the same sonically. The older GTs are preferred by many, but can't be used in all the Atma-amp tube positions becuase the can't handle as much current as the GTA/Bs - they seem to be fine in the preamps. I think you hear more about the Bs because thet are more readily avaiable. |
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. . |
This is a very interesting thread. Trcnetmsncom, I looked up the impedance curve of the Avalon Eidelon. It's below 5 ohms (closer most of the time to 3 ohms) between 50Hz and 20kHz, except for a narrow "peak" in the midrange, where it gets up to 7 ohms. This is not an optimal match for any OTL (like the Atma MA2) that does not use negative feedback to achieve a low output impedance. However, the MA2 has such huge power capability that you are able to overcome the impedance matching problem to a large degree. Nevertheless, I wager that if you were to interpose a pair of Paul Speltz's Zero autoformers between the amp and the speakers, the perceived unpleasant treble distortions would disappear. Given the large investment that you have already made in the amps and speakers, the Zeros amount to a trivial additional expense. I don't think one can ever talk about how an amp "sounds" without considering the speaker load. |
Lewm, Thank you! That is very interesting. In fact I wanted to research the same, but then was too busy to do so. By the way, it was the cable breaking in not the Atmas after all, when I began to seem to hear the same "thinness" through the Sound Labs, which Trcnetmscom had described hearing through the Avalons with them. Wanted to report that anyway. Cheers, |
Since we are on the topic, sort of, what are your preamps of choice with the Atma amps. I assume the Atma pre would be a natural pairing. Was that best for you? Have you preferred something else? Why? Or tried others and decided the Atma pre was best for mathcing with their amps? Why? Your thoughts? |
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Hello Lewm, Thanks for the research and posting a response. I'm sorry if you got the impression from this thread that I own the Atma's. To be clear, I do not. I came awfully close though! However, I was fortunate enough to have spent time hearing the MA-2 with the speakers I own and speakers I previous owned in three different systems for a total of 5 lengthy listening sessions. Thankfully I was able to get over the things I thought they did so well and hear IMO what did not jive to my ears. When I talked on the phone with Ralph he mentioned to me that there were many Eidolon-Eidolon Diamond/MA-2 users in the field. I don't know for certain, but I didn't get the impression from talking with him that any of them were using the Zeros. If this helps, the MA-2's amps were able to drive the Eidolon Diamond to extreme volume levels without signs that the amps were running out of gas. Also, it might be of help to know I heard the IMHO texture thinness and treble abbreviations at low or loud volumes. But from the little technical knowledge I have of OTL's, tonal abbreviation is independent of volume. In other words, if the speaker in question is not a good match for an OTL, tonal coloration will be apparent at all volume levels. Is this correct? I would like to point out once again I think the Atma's are in certain ways .... "extraordinary" .... exceeding the competition. I also encourage others to audition them to hear the certain areas of cutting edge performance I feel Ralph has achieved with his design. Having lived and learned over the years from owning five different sets of electrostatics from Acoustat, Quad, and Martin-Logan, these also in certain ways were ....extraordinary.... and in my view, above, exceeding that of the competition. But they also lacked in certain ways, and for me in the long run their faults took away the enjoyment, that magic, the escape, the thrill of being fooled if only for a second that this could be real. Through my experience and from the mistakes I felt I've made, I have learned a balanced approach of choosing all components is what has endured for me. Best to all, Tom |
Hi Pubul57 My MP-1 Mk. III developed a problem due to shipping, which absolutely without Ralph's fault is not yet resolved. I had occasion to borrow a WAVAC which to my ears mated perfectly with my MA-2 Mk. IIIs driving my U-1PX Sound Labs. I was so enthralled with this combination that I later bought one used here on Audiogon, tube rolled the Ruskies for Mullards and am happy. Once my problem with the MP-1 is solved, I'll compare and sell one of the two preamps. Hi Tom, I've followed your advice digging out all sorts of jazzy software I could find on CD, LP and Steve Nugent's "SPOILER", a wonderful USB-DAC by the way, clobbers Zanden and the dcs-stack, and could -perhaps would(: not - hear what you did. As I noted above, at first I thought I had it pinpointed, but then it turned out it was an IC, starting to break in causing that anorexia in sound, which thanks to the Audio gods soon gained sufficient weight again to be out of danger... |
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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. |
Has anyone seen the new review of M-60 and MP3 in Absolute Sound? I am still waiting for my issue to come in the mail. BTW I use PS Audio Duet on my MA-1's. My MP-1 is plugged into Poew Plant Premier. I have always used the Duet on the MA-1's. I used to have much older MA-1's, and when I first got the Duet and plugged the amps in I though they were cleaner. I really should try taking the Duet out and see what the latest amps sound like right in the wall. I have also never tried the MP-1 direct to the wall. I guess I just have to much faith in PS audio power gear. |
For some reason, the MP-3 doesn't seem to get the respect of the M60s, and I wonder if this is due to the phono stage. As a line stage it seems to let the M60s do the transparency, microdynamic detail, incredible timbral accuracy and expansive soundstaging thing that the amps are capable of. I've tried a Joule LA150MKII and Dodd Battery pre with the M60s and they sound quite different (and more similar to each other) than the MP-3 with the M60s (both warmer and plumper in comparison). To my ears, the Atma-spere pre is an important part of getting the Atma-sphere "sound" - for better or worse; I like what the whole package can do, and to my ears there is no better amp that I've heard with my Merlins than the Atma-spheres; that first amp after many tries, where I found an amp that let me sell my CAT JL2 with no regrets - at all; I prefer the Atmas with the Merlins - though I suspect the CAT can do its "thing" with a very wide array of speakers. |
Just a comment on NOS tubes. I have been rolling a few and I jst want let it be known that all tubes I have received from Andy Bowman at Vintage Tube Services are clearly matched and quiet, very quiet. With other sources I have not been so lucky. I'm sure you can get well matched from other sources, but Andy has never failed me. |
My favourite combination in the MP3 (2 12au7, 2 6sn7s, and a 12at7 not in audio circuit)is the 1940/50s RCA 12au7 Blackgate combined with the Sylvania 6sn7GTA (not sure GTB would make any difference). I tried the RCA Cleartop and Siemens 5814 which seem some what similar to me, compared to the Blackgate 12au7. I use the pre with the M60 amps and I think the 12au7 lends a touch of warmth which is a nice touch with the neutrality and transparency of the amps and my Merlins. The RCA 5814 seems very similar to the Blackgates. My combination definitely performs very well for my music and ears, but I don't doubt there may be even better combinations out there, but I'll stick with this for a while. P.S. I use RCA combined with Sylvania GTBs in the amp - 2 RCA in front 2 Sylv. in rear slots; I prefered this to all Sylvania. This being said, the Atma-spheres sounded great with any of this combinations, it is just a bit of spicing to a basic recipe. |
Hi Honest1, Too early to say, I'm afraid. Thanks to their huge power reserves they wouldn't clip where the Atmas did, also it seemed to me, that on the piano LP I listend to, they rendered the decay of notes better than the Atmas, but I'm not sure at all. I was so taken in by the music, that I did not want to do direct comparisons. I'll do that later and keep you posted by mail. Cheers, |
Detlof, That would be a very interesting comparison, but I would urge you to hear the Atma's at their best. If you haven't already I would replace the filament fuse with a premium fuse. Such a nice improvement for around $75 total for the two fuses. Not sure if the VTL's are in need of premium fuses - but it might be worth asking. |
Honest1, all I can say at the moment, that both amps are true to the music. Speaking of the Atmas, the amps give you a sort of middle of the hall placement with most classical recordings and a midrange which is impeccable, adding nothing, taking nothing away. However, if things get really loud, they do clip on the Sound Labs. The VTL's with their 600 pentode watts don't, they move you closer to the stage, are more powerful in the lower bass regions, something you don't miss though with the Atmas, because their blend between mid , highs and lows is almost perfect. Listening to the VTLs is like changing your seat more to the front, closer to the music, which is represented most realistically. I still have to find something to fault them. But getting that close, also in a real concert can have its drawbacks, you tend to concentrate on details, instead of taking in the entire "gestalt" of the music, which the Atmas achieve beautifully. In listening to jazz-combos, the VTL throws the happening right into your room, with absolutely uncanny realism and rocks teady players in excellent three dimenionality. The Atmas are a tad more polite, also again here a little more laid back, but in their way just as musically convincing. Both amps are excellent achievements I would say, at least to my ears. |
I have received two days ago a new pair of MA-1 MK 3.3 fully loaded (with VCaps and Powerboost add-ons). It is not even properly burned-in yet, but I’ve just had the most spectacular listening experience in my life! I’m thrilled!!! MA-1 & MP-1 MK 3.3 are impressive, outstanding and totally fantastic! I’m listening to them with a pair of old pairs and heavily modified Soundlab A3. The synergy with A-3 is exceptional. The sound of Atma Sphere combo is simply spectacular and stunningly beautiful. It outperforms by light years anything else I’ve had or listened in my life. Please notice, I’m far away from being a beginner in the audiophile world. I owned EAR V12, 509, 912, Quad II forty, eighty, 606, 909, I have tested or used a couple of McIntosh, Primare, Jadis, PassLab, Spectral, and many fine machines I do not remember any more. I was afraid of the heat coming from 38 tubes, but finally, it does not heat so much. I find it acceptable in my moderate-size listening room. My other concern was the size of A-3 and the synergy with MA-1 (many audiophiles buy very powerful transistor amplifiers to drive them) but their curved shape actually works just fine in moderate size room and the synergy with MA-1 is the Perfect Match! I will receive in a couple of weeks a new DAC from Abbas audio, but even now, on my budget CD player, I have the most fantastic sound I have ever experienced in my life (my previous DAC was Big 7). I fully and totally understand how privileged I am to own Atma Sphere gear. If you have money to buy it, do not look elsewhere! If you live in Paris area and you would like to listen these magnificent amplifiers, feel free to contact me, I’ll be happy to invite you for a listening session. As many other guys do, I like to listen and compare various gear. This time, I’ll gladly compare some new DAC, turntable, cables (I use Magnan’s and WhyNot), but in a matter of amplification, for me things are settled. I will not bother to try listen anything else anymore. This is a definitive purchase for me. I am in a state of Nirvana. Truly exceptional amplifiers and pure and utmost joy. |
@twodolphins If you have older Sound Labs, prior to the 'toroidal 2' backplate, there are some simple modifications that can be done to improve their impedance and efficiency. This makes them sound better too! This involves removing a resistor in the crossover. Contact me offline for more information (or look into getting the backplate updated by Sound Lab). |