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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

ozzy
ozzy's avatar
ozzy OP
7,648 posts
 

Charles,

We are on the same page. But, you've got to give Atma-Sphere and Ralph credit for allowing an ongoing upgrade path for his components. So that in itself will mean long term enjoyment with the latest and greatest version of his equipment.

ozzy

jond's avatar
jond
6,057 posts
 
ozzy glad to hear you're enjoying the amps and not already thinking about your next amp,  at Audiogon we call that progress :-p. Seriously though have fun roll tubes and just settle into that sound for a while I am sure its going to continue to improve for you. Happy listening!
charles1dad's avatar
charles1dad
10,250 posts
 

Hi Ozzy, I certainly acknowledge and give  credit for a well thought out long term upgrade/updating pathway.

Charles

sdrsdrsdr
196 posts
 
Doesn't using zero transformers defeat the whole point of an OTL amp? It's putting  a transformer in and makes it similar to a non OTL push pull tube amp.
almarg's avatar
almarg
9,670 posts
 
Doesn’t using zero transformers defeat the whole point of an OTL amp? It’s putting a transformer in and makes it similar to a non OTL push pull tube amp.
That’s a logical question, which has been stated here in a number of other threads in the past, but basically the answer is "no." From a technical standpoint the following statements quoted from the FAQ at the zeroimpedance.com site are good ones IMO:
12) What is the difference between the ZEROs autoformer and a typical tube amplifier’s transformer?

The ZEROs have a few advantages over "typical" tube amp transformers:

A) The music comes out on the same winding wire that it goes in on so the music does not have to pass from a primary winding to a secondary winding.

B) There is no DC current to contend with. When a transformer is made to accommodate a DC field, its audio transparence is compromised.

C) The impedance ratio is very small (16 ohms to 4 ohms, compared to a few thousand ohms to 4 ohms). This simply means that it is much easier to achieve things like, frequency response extremes, than with a "typical" tube amp transformer. The ZEROs sport a frequency response of 2 Hz to 2 MHz.

13) Doesn’t adding the ZEROs to my Output-Transformer-Less (OTL) Amplifier defeat the benefits of the OTL design?

The ZEROs were originally designed to maximize the full benefits of the OTL amplifier by changing the speaker’s load impedance to the Maximum Power Transfer Region of the amplifier being used.

The ZEROs are not an amplifier fix, they are a speaker fix. It is a great disfunction to music loving audiophiles for speaker manufactures to be making 4 ohm speakers with 3 or 2 ohm impedance dips, and then expect amplifiers and speaker cables to be able to transfer music into a load approaching a dead short. The ZEROs simply multiply the impedance of the speaker in use, and do it so transparently they provide greater benefits than the "penalty" of an added component.
As I said, from a technical standpoint that all makes sense to me. Basically, all transformers and autoformers are not created equal :-)

Regards,
-- Al

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