2. amps-preamps
  3. 128359-41

Amps Atma-Sphere M-60 Mono blocks OTL design

I just purchased a used OTL Atma-Sphere M-60 mono blocks that I have sent to Atma-Sphere to be upgraded to the current model 3.3 and I also added the option of a higher quality power supply and V caps.

I have sold my old trusted Eggleston Andra 2’s speakers and have built some monitors using Aurum Cantus ribbons (102db) and Aurum Cantus midwoofers (90db) that are both rated as 8 ohm nominal. I have a DEQX Premate and will be crossing over to (2) JL Audio F-113 subs at 80hz.

Currently I am using a solid state high power stereo amp (Pass Labs) that I used with the Andra 2’s.

The Atma-Sphere M-60 is rated at 60 watts class A and is said to work better with higher impedance loads.

It will probably be a few weeks until I get the M-60 and was hoping someone could provide opinions of what to expect.

I listen to late 60 early 70’s classic rock music mostly. Sometimes loud.

ozzy

128x128ozzy
gdnrbob
4,460 posts
 
Thanks Ozzy and Almarg.
You guys are the best.
Bob
atmasphere's avatar
atmasphere
11,960 posts
 
So far we've yet to hear about any hum problems with the Sophia or TJ Music tube. Al's report is the first I've seen.

We made a circuit change in our amps regarding how our filament circuit is handled about 12 years ago. That really reduced the hum issues caused by cathode/filament leakage; every now and then we run into a bad tube in the field causing a problem but its nothing like it was before we made that change. So I suspect much relies on the circuit design.

FWIW in our preamps the leakage would be a non-issue.
gdnrbob
4,460 posts
 
Ralph, I am still awed by what your amp and preamp can do.
After growing up on tubes, I never thought I would return to them, but, you did it.
Bob
lowrider57's avatar
lowrider57
5,417 posts
 
Was wondering if anybody has tried audiophile fuses in Atma-sphere gear? Does the design make a fuse change irrelevant?
atmasphere's avatar
atmasphere
11,960 posts
 
We've got a lot of positive comments from customers using audiophile fuses.

The location on the amps that makes the most difference is the one by the power cord. That is also the one that is most likely to be blown, as a power tube failure can blow that fuse. The other fuses only blow if there is a serious service issue with the amp; over the last 30 years I can count those failures on one hand.

Because there are three fuses rather than just one, the sonic effect of the fuse is reduced somewhat but you can still hear it.
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