You might have to upgrade or replace your current preamp that you are using at the moment since you will be missing the finest tubey sound. If you have 8 ohms speaker that will work fine with M-60 but if you ask Ralph he recommend to use 8 and16 ohms speakers. High end 16 ohms speaker such Classic with built-in horn mid range and tweeters are pricey. The only alternative way to gain 16 ohms is through Zero transformers.
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