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

sksos1,gdnrbob,

Thank you so much for your comments. So with my set up these Amps should work fairly well?

My thinking is the Atma-Sphere M-60's will not have to power anything below 80hz and with my present 90db+ speakers they should work really well?

Did either of you have the V cap and power supply upgrade?

Yes... 

Unless your speakers are very efficient (e.g. say 94db+) you will most likely want to get a set of Autoformers from Anti-cables to boost the impedence of your speakers to reduce the load on the M60's.

http://anticables.com/autoformers
ozzy that's the only way we have ever ordered any Atmasphere gear, with both the V-cap and Power Boost upgrade.

As for will it work well with the speakers you describe? Ralph would be the best to answer that.

(Dealer disclaimer)

bassdude,

Thanks for the info.

You really think I will need the Zero's if the M-60's will only need to power 80hz and above?

sksos1,

Can you comment on the V caps as to how many caps are involved, and what exactly is the Power boost upgrade?

Ozzy,
You said the speakers you have built are 8 ohms. Assuming that there are no widely varying impedance dips below 5 or 6 ohms (particularly in the mid to upper bass region) I don’t see the necessity of using the Zero transformers.  Someone above mentioned a 94 dB sensitivity as a cutoff point and I disagree with that.  Zero transformers are used to increase speaker load impedance as seen by the power amplifier.  It has no meaningful bearing on the speaker sensitivity. 
Charles