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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
ozzy's avatar
ozzy OP
7,466 posts
 

gdnrbob,

The rated FR is 37 to 4000hz. But that is probably with a ported design and to me would be very subjective anyway. I would say reasonable / usable low end and a non ported design would be about 50-60hz.

ozzy

gdnrbob
4,444 posts
 
Wow, not bad. I own a pair of Zu Omen Bookshelves. They have a similar range, and I like their simplicity (crossover-less). I find it amazing that such a small enclosure can still reproduce such low frequencies.

Will you be adding subwoofers? Looking at the DEQX and its' capabilities, I would imagine that your DIY speakers and a pair of subs could possibly out perform your Egglestons.
Perhaps you could build those, too?
Bob
ozzy's avatar
ozzy OP
7,466 posts
 

gdnrbob,

Yes, I do have (2) JL Audio F-113 subwoofers. With the DEQX  I am crossing over at 100hz. And yes, this combo far exceeds my Egglestons. I sold them.

Well my 72 hour abstinence is complete! I just turned back on the Atma-Sphere M-60's with the NOS 1970's era Russian 6H13C output tubes and the RCA 1950's era  6SN7GT driver tubes.

ozzy

atmasphere's avatar
atmasphere
11,806 posts
 
@ozzy , make sure that 6SN7 that sits in the front by itself is a -GTA or -GTB. That particular position has more voltage on it and the older GT style tubes will have a shorter life in that position. FWIW the Russian and Chinese tubes marked 'GT' seem to be OK in that position.
ozzy's avatar
ozzy OP
7,466 posts
 

atmasphere,

I know many that I have were listed as GTB but the writing on the glass tube is gone.

Any way to physically check it ?

ozzy

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