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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
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almarg
9,670 posts
 
Hi Bob,

I don’t recall anyone reporting having used a DEQX with a time coherent speaker (e.g. Vandersteen, Thiel, Green Mountain Audio).

BTW, time coherence implies phase coherence, but phase coherence does not necessarily imply time coherence. Many speakers are phase coherent without being time coherent. See the post dated 7-15-2014 by Roy Johnson of Green Mountain Audio in this thread:

https://forum.audiogon.com/discussions/sloped-baffle

As you've probably seen in the past, though, John Atkinson’s measurements that are presented in conjunction with most speaker reviews in Stereophile sometimes provide impulse response graphs (and associated commentary), and usually provide step response graphs, which can also provide insight into time domain performance.

Presumably the time alignments provided by DEQX would not provide a benefit in the case of a speaker that is inherently time coherent, such as your Treo. But of course the frequency response and room corrections it provides would presumably still be applicable. As well as preamp functionality that is provided by some models, and A/D and D/A converter functionality.

Best regards,
-- Al

gdnrbob
4,444 posts
 
@almarg , et al.
Considering how much you are doing to the original signal (when processing through the DEQX), do you think you are altering it to something 'unnatural'?
Bob
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almarg
9,670 posts
 
Hi Bob,

It is certainly possible to overdo the DEQX calibrations/corrections, resulting in unnatural sound. But as my dealer advised me (Nyal Mellor of AcousticFrontiers.com, who is wonderful), corrections should be applied conservatively. Especially with respect to the natural upper treble rolloff that most speaker/room combinations tend to have at the listening position.

My Daedalus speakers are rightly known for having a very natural sonic character, and that was only improved as a result my use of the DEQX. Most notably in the case of recordings having sound quality that is mediocre or worse, especially in terms of harshness or excessive brightness in the treble region. As I said in one of my posts in the DEQX thread:
Perhaps most notable among the differences that I and my wife perceived were on some recordings having overly bright string sound, including some string quartets as well as symphonic recordings. Those became much more enjoyable with the filters engaged. Not because the sound was dulled down, but because there seemed to be increased detail and improved definition in the upper midrange and lower treble, as opposed to a more homogenized presentation of those notes, which in turn resulted in the brightness being less objectionable.
I can say also, in the case of my HDP-5 and as Ozzy and numerous others in the DEQX thread have attested to in the case of other models, that with the corrections bypassed the unit is amazingly transparent. Even when an analog source is being used (via unbalanced connections, at least; I haven’t used its balanced analog interfaces), and is therefore processed through the unit’s A/D and D/A converters. I can’t say that there is zero effect on the signal, but it is remarkably small, and easily outweighed by the benefits the processing provides.

Best regards,
-- Al

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ozzy's avatar
ozzy OP
7,466 posts
 

steakster,

First off I am getting older and my Eggleston Andra 2 speakers were 215lbs each. Moving them around the room is no fun. I always wanted to try tube amps but I knew that my Andra’s required a fairly hefty amp to drive them properly.

Once I got the DEQX Premate with its built in subwoofer crossover, my brain juices started to flow. BTW, I also retired 2 years ago so I now have extra tinkering time available.

Anyway, I wanted to make a very easy to drive stand mounted speakers to use with my JL Audio subs. I made a prototype with some drivers I bought on EBay. They actually sounded pretty good but the cabinets still looked very DIY (I own a jig saw and a circular saw and haven’t changed the blade in 30 years)!

I then found on Parts Express some really nice Hi Gloss cabinets with the internal volume and size I was looking for. So keeping with Parts Express, they sell the Aurum Cantus G1 ribbon tweeters that can handle 100 watts rms. (I have always loved the sound of ribbon tweeters). I then thought keeping within that family line was the top of the line Arum Cantus 6.5 mid woofer. It had the specs that I was looking for. Well, the 6.5 mid woofer really turned out to be a 7" size and the High Gloss cabinets were a pain to cut. The front baffles are 1 1/2" thick !

But I did it, and they look great. I stuffed them with " acousta stuff". I wanted to be able to experiment with different crossover settings so I built an external crossover box. Well as I started trying more and larger caps and inductors that box became too small and I made a larger one with spikes! ( BTW, I ended up with all Mundorf silver, Gold, Oil caps).

Anyway, it has been a fun challenging project that I am really proud of. I have listened to many systems and I think I have a winning combination! Total cost about $2600.

Thank you for asking...

ozzy

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