Atma-Sphere MA-1 amps

Interesting. Some questions for the newer owners:

1. Can you adjust the bias yourself? Or is it pre-set at the factory and does not provide for manual adjustment? (Mine have a manual bias adjustment. The sound improves significantly as you push the bias toward the recommended setting, but tubes blow more frequently at that point.)

2. Is there a built-in bias-meter? Does the bias remain steady? I have a digital multi-meter to measure bias, and there is a fair amount of variation in the bias reading before it eventually settles down.

3. How frequently do tubes blow? Is there a simple way to tell which ones have blown? (My eyes are no longer good enough to see the very thin wires in the tubes that indicate whether they are good or not.)

4. Do you use upgraded power cables? Was there a material difference when you first installed them? In what respects?

5. How much of a warm-up does it take to bring the tubes to the prime listening point? I found that it took 24-48 hours to get to that point, so I eventually would leave the amps on for days at a time. Sound was improved, heat was not good, tube life was not good.

I think you should talk with Ralph directly; you will get straight answers and he will not jam his gear down your throat; you will also gain a perspective of his goals and objectives that he is trying to acheive thru his designs;I have had this experience directly;well worth the call.

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).

I own a pair of MA-1 Mk.IIIs and an MP-1 Mk.III linestage+phono. I could tell you how much I enjoy this combo, but I'd just start gushing. Both are quite revealing of up and down stream componentry and both become even more magical with NOS 6SN7s. I've spent time with the M60s, MA-1s and MA-2s - there are differences across the members of the Atma-Sphere lineup, but within the same revision level, they share the same design, many of the same bits, and to my ears sound more similar than different. Reviews of the M-60 and MA-2 are a bit more prevalent and they should give you a pretty good word picture of the sound of the MA-1.

At present I'm using 4 Ohm Audio Physic speakers (Avantis) and the MA-1s drive them just fine. I've tried them with and without the Speltz Zero Autoformers, and while the Zeroes work as advertised they are not entirely without their own sonic signature. Different speakers yield different results, but in no way do I find the Zero mandatory on my 4 Ohm spkrs.
 
Tim
 

Jtimothya, I know what you mean about gushing. I was thinking about Atma-sphere amps for a long time as I knew that my Merlins were very OTL friendly, but I was not so quick to change from my CAT JL2 which is a mighty fine amp. Well I finally pulled the trigger and let's just say I understand why there is so much brand loyalty for the Atma-sphere gear. With the right speakers (perhaps fewer limitations with the MA-1 and 2), OTLs are very special indeed, and the M-60 seems to be perfectly suited in terms of power for the needs of my speakers. I think Tim Aucremannk's review in Soundstage is very well written and captures the Atma-sphere sound very well.

As far as SS, I've not heard better than the Pass XA-30.5, and I assume Nelson's higher powered versions are just as good, and necessary for less efficient speakers.