Genesis of the RM-10 MkIII

Some of you may be curious as to how the concept of a MkIII version of the RM-10 amplifier came about. Well it all started in the Fall of 2018 It was the Fall of 2018 when Roger first learned of his cancer diagnosis. At that point while I had known him about 15 years and had been working with him four years. I was shocked to say the least and after a few weeks we spoke about Roger’s goals for the transition of the company. He was adamant that it should continue and wanted me and a couple other of his friends that I knew to take it over upon his death. In the meantime, Roger had decided that there would be two projects he would like to finish before the disease prevented him from doing physical work. The first project was an evolution of the Music Reference OTL-1 output transformer less amplifier to be based on Julius Futterman’s H-3A circuit that was brought to production by both Harvard Electronics and Tech Instruments. Roger was making significant improvements to the circuit and produced a working pair of monoblocks but could not complete the project as the disease had finally taken a toll on him physically.

However, Roger’s mind was still sharp and so we set out to plan the second project which was the Music Reference RM-10 MkIII. When Roger moved up to the Bay Area from Santa Barbara in 2014 one of his goals was to focus on teaching and developing audio educational programs. So, he founded the Berkeley Hi-Fi School and began tutoring students, some of whom became interns and worked on some projects with us. In addition, he wanted to start formal DIY classes along the lines of the Randall Museum where students could build their own components as part of a curriculum of courses. Roger felt the RM-10 MkIII would be the perfect amplifier for the first class. Once Roger thought this project through he and I discussed the design philosophy and what needed to be done to bring this project to life.

I cannot say the process of working with Roger at this stage of his disease was easy. While his mind was sharp, he tired easily and was in significant pain. It made discussing and debating concepts much harder than it was previously before the disease took hold of him. So, when he told me that one of the first design changes for the amplifier was that the circuit would be laid out on a printed circuit board (PCB), I was not entirely happy. It wasn’t that Roger had never used PCBs in his designs before so much as it was the RM-10 had a reputation of being an easy to build, reliable, and if needed serviceable point-to-point wired amplifier. However, Roger felt that today’s PCBs were of much higher quality than when the original RM-10 debuted and he could lay out the circuit such that it would still be easy to build, reliable, and serviceable. In my experience I knew where to cut my losses with Roger so there was not much pushback from me.

The other aspect of the design Roger changed was that this would only be a stereo amplifier and not be switchable to monaural operation. This design change really ruffled my feathers, and we debated on this decision for quite some time. Unlike the PCB decision this one was not related to anything having to do with difficulty building, reliability, or serviceability. In the latter part of his career Roger started trending towards building lower watt amplifiers. One they were easier to design (at least for Roger), two they were lighter, and three they were lower in distortion. Roger often mentioned that audiophiles should buy a power meter and really understand how many watts they were using to listen to music. Other than musical peaks less than a couple watts were needed to get optimal sound pressure level (SPL). Factor in the low distortion and the amplifier not having to work so hard to produce adequate volume and you have a recipe for great sound. At this time Roger was also using tone bursts to measure his amplifiers, and he noted that even though an amplifier design might yield 8 or so watts, if designed properly it would be capable of handling 20 watt peaks. In the end after a long debate Roger quite loudly said, “35 watts ought to be enough for anybody.” End of discussion.

Unfortunately, Roger passed away before we could really get started on the project, so it was up to the rest of us to make the RM-10kIII a reality. We enlisted the help of Scott Frankland the owner of Scott Frankland & Associates to be the lead engineer and develop the layout for the PCB. Scott is very familiar with Roger’s designs and was instrumental in helping us not only with the PCB but the digitization of the top plate layout. We used Roger’s philosophy for parts selection, and we were able to get the transformers wound to original spec by another third party. Neal Rasmussen at Neal Faye Designs who Roger worked with in the past was kind enough to make the top plates for us. The only other area where we diverged from the original design was the wood frame which we beefed up a bit versus the frame used on the RM-10 MkII. As the original RM-10 was the first circuit design to achieve 35 watts from a pair of EL-84/6BQ5 tubes, the core design philosophy remains intact. For reference you can read about it here in the manual’s Design Philosophy section.

When it came to determining the price of the what a fully built RM-10 MkIII should cost it would be worth noting that Roger lamented at how high the cost of the RM-10 MkII reached over the years. Even though we were able to justify the cost Roger was still not convinced it should be that high. I do not know if it was the disease or if Roger was a bit out of touch with the times, but it was his goal for the cost of a fully built amplifier to be sub $2,000. As we were progressing through the project and experiencing delays, including a lengthy one during Covid, as well as added costs it became clear that we could not meet that goal. Given that the Berkeley Hi-Fi School would no longer exist it became evident that we could compromise and offer fully built amplifiers at $3,000 and kits for the DIY crowd at $1,650. So, nearly seven years in the making the RM-10 MkIII has become a reality. We have been somewhat slow to go to market but are selling kits and fully built amplifiers. Hopefully with some added market exposure we can sell some more and make Roger proud and some customers happy.

Music Reference RM-10 MK III Kits

RAM Tubes is pleased to announce on the 6th anniversary of Roger’s passing that a select number of RM-10 MkIII kits are available for purchase. The build level is rated as difficult, and you should consider yourself to have advanced DIY skills and knowledge of audio electronics concepts and circuits, as well as the proper equipment to do the job. Note that RAM Tubes will not provide support for the DIY build.