Music Reference RM-10mkiii Kit

The OTL -1 is also a  phenomenal amplifier, the best I have had driving my AG Trios.  It is unfortunate so few of these were built, as they are giant killers with high efficiency speakers.

In the introduction to his instruction sheet for biasing the  amplifier, Roger states that he felt this was his best design.

The last 5 years have been tough for manufacturing and businesses all around. Even this last year with tariffs, it's one thing after another, that small business have to deal with. Manufacturing to scale is a crazy up front investment, so I completely understand. 

I really think the RM-10 is the perfect amp for most people; it's space friendly, as well as cost and energy efficient. At least on the west coast, we love our JBL's and the RM-10 is great with them (almost all of them). I think the RM-10 would appeal to tube amp lovers who have SET's because the RM-10 offers a little more grunt for the low end without sacrificing tone. I wish I had studied electrical engineering.

I read a review of the OTL-1 awhile back and it seems amazing. I am not sure what the typical characteristics of OTL's are? Similar to SET's? How is the damping, because I assume they are low powered and could be mated to high efficiency speakers with large woofers. 

Depending on the design demping will vary with OTLs. I have owned both Atma-Sphere and Roger’s OTLs. Ralph Karsten uses very little to no feedback in his circuits and as such the damping is low. Atma-Sphere OTLs are also based on the Circlotron architecture. Roger’s OTL is based on Futterman’s totem pole design and not only uses feedback but has an impedance matching inductor that allows the amp to see a 32-ohm load whether you use the 2, 4, 8, or 16 ohm taps. There is also a direct 32 ohm tap if you want to bypass the inductor. The damping, which is on the high side, and conversely gain can be adjusted based on how you use the feedback wire which can be attached to any of the taps regardless of which one you are using for the speaker cables. If you want to learn more here is the manual:

 https://static1.squarespace.com/static/61d0e00ac8fd8f2d31e7f907/t/65409de3490f124354d9f737/1698733543099/OTL-1+Manual.pdf

I expect your efforts with the RM-10 will be worthwhile.  Many years ago I bought a RM-100 to match with Vandersteen speakers.  It was one of the favorite amps among the many I owned.  At one point I was curious about the RM-10 but felt my speakers at the time would not have been a good match.  I had/have high regard for all of Roger's work.

RM-10’s (in both original and Mk.II iterations) show up occasionally on the used market, selling for around $1200 to $1500. Have your cash ready to pounce on one when it shows up!

Roger designed the RM-200 for low impedance loudspeakers, and produces 100 watts (into all loads) from only a single pair of output tubes per channel (while retaining long tube life). The RM-9 also remains a favorite of classic tube amp design (Dick Olsher prefers it to both the McIntosh MC75 and Marantz Models 8 and 9).

I am a former owner of Audio Research and Atma-Sphere tube amplifiers, but now have settled on RM-9 Mk.2, RM-10 Mk.2, and RM-200 Mk.2's as my "remaining life expectancy" amps. I will never sell them.