Music Reference RM-10 stereo vacuum tube power amplifier. (Components).
Source: Manufacture's Loan
Reviewer: Tom Lyle
The Music Reference RM-10 isn't puny, but I'm tempted to use that word to describe its appearance because that's how I felt when first unpacked it. These days, with 3 watt per channel single-ended amps flooding the market at first glance one might suspect that this amp is one of them. But the RM-10 puts out a healthy 35 watts per channel, and according to its designer, Roger Modjeski, "performs better than any other 35 watt per channel amplifier I have listened to or tested." From the experience he's had in his lifetime outlined in the owner's manual, this probably includes countless models. And from my listening experience in both of my systems over many months, he's probably right.
One of the reasons I thought the amp looked so diminutive is its output tubes, which is a pair of rather small EL-84s per channel. These tubes are only about a third taller than its two 12AX7 input tubes. This diminutive amp makes some mighty claims in the owner's manual's specifications page, such as that the amplifier is flat within 0.1 dB over the entire audio range, so that it will "not affect the tonality of instruments or complex combinations of them". It has a low distortion rating of .3% on average level material when played below clipping. Mr. Modjeski says that he has found that high distortion, even if only second harmonics causes "muddiness in music more complex than a soloist". And unlike some transistor amplifiers, in which distortion rises in both percentage and order at low levels, the RM-10's distortion falls as level decreases.
For months I used this small tube amplifier in my second system in the basement hooked up to my 4-ohm stand mounted PSB Mini-Stratus speakers. Not did I think it unworthy of my upstairs system; its just I thought there was no way it could drive the larger speakers I was using at the time. It wasn't until I got off my butt and read the "owner's manual" (the explanation of why that's in quotes later) did I realize that it could have very well been used in this system with excellent results. By the time I brought it upstairs I was using the even larger Sound Lab Dynastat electrostatic-hybrid speakers. To my surprise this amp drove these speakers to more than satisfying levels on all types of music. Sure, this amp was hardly powerful enough to consider it a good match for these speakers. And I used a subwoofer in this system, and that certainly helped, but still, it clearly demonstrated that I should have brought it upstairs earlier.
Read the Manual: I suggest that the purchaser of this amplifier not make the same mistake I did, so after unpacking this unit--read the owner's manual. This treatise on the RM-10's design and use explains its raison d'etre, as well as instructions on its care and feeding. Basically, this amp is of the "plug and play" variety, other than the setting of the tube bias, which is the first thing covered in the manual. It requires one employ a user-supplied voltmeter for its adjustment. The good news is that I didn't bother setting the bias until late into the review period, and it was off by only a few millivolts. Adjusting it to dead center didn't seem to affect the amp's sound. The second thing that's covered is the fuses, which are specified as being "very carefully selected". They output fuses are of the relatively uncommon 5 x 20mm, 160 mA slow-blow variety, and a couple of extras are supplied with the unit. Also mentioned is that the six tubes in the RM-10 have also been carefully selected by RAM Tube Works to "ensure their long life and reliability." Next up are a couple of quotes, one by Marshall McLuhan on the relationship between advertising and product satisfaction or the lack thereof, and another by Henrik Ibsen on the value of living life to the fullest in the times one is living in.
In a section titled "The Designer's Tale," Mr. Modjeski essentially tells his life's story--from his early childhood experiences with tube amplifiers, to his to running a hi-fi repair shop in Richmond, Virginia, to opening a high-end store, to working for Harold Beveridge, and to finally founding Music Reference in 1981. Along the way he tells hard lessons learned such as the benefit of manufacturing units with overbuilt component construction and short-circuit-proof power supplies, among many others. It is quite a long section of the book. After that, is the "Design Philosophy" section, where he explain in quite some detail the underlying principles behind the RM-10's design--all stemming from the realization that it only took a couple of watts to drive his old Quad electrostatics to satisfying levels. But he also realized that with a low power amp it "better behave well in clipping", and he wanted the RM-10 to be known as a "gutsy" amp. He goes on to discuss the principles behind getting 35 watts out of an EL-84 tube, and the way he uses very high quality transformers. There are some details, too, such as how that after a complete examination of the currently available binding posts that would fit the cost criterion of the RM-10, he decided to have his own made of solid brass that allow the use of a 3/8" nut driver to tighten them.
There is also a lot of technical mumbo-jumbo that is actually quite entertaining to read even I didn't understand all of it. But that doesn't last too long until he gets to the fact that this amp was designed for speakers such as his original Quads, and the reason it can be used in speakers such as these is the attention paid to lowering the amp's noise floor--along with all the other criteria that he put ahead of just building just another ordinary 35 watt tube amp. This took four years from idea to fruition.
After that, the manual has sections on specifications; input connections; how to further eliminate noise; his theories on interconnects; connecting the speakers; adjustments, fuses, tube considerations and Life; gain adjustments; servicing (Tips for Qualified Technicians Only!); and schematic drawings.
Driving Experience(s): During the time it spent driving the PSB Mini-Stratus speakers I fed it all types of material, and much of it came sourced from my computer when I was performing digital editing tasks. But much of it also took place when I was doing some serious listening, and although it sounds like a cliche, the amp just got out of the way and let me enjoy the music. The amp was powerful enough to drive the relatively insensitive 4-ohm load, and never did I feel like I was missing any musical material by not using the solid-state muscle amps I usually use, a pair of Muse Model 150 monoblocks. But when I did notice the amp, it was in a positive way, such as its extended, grain-free treble, its crystal clear yet luscious midrange, and remarkably tight mid-bass.
There are so many albums that I played through this rig that impressed me, but what keeps popping up in my head is the newly remastered version of The Rolling Stones' Let It Bleed. Sure, the SACD layer on the upstairs system sounded better, but the CD layer is extraordinary, too. It's quite a revelation to realize that the 'Stones' sessions were quite carefully recorded back then, and all their choice late 60s and early 70s albums bear this out.
I don't know where to start to describe how the RM-10 contributed to the excellent reproduction of this album. Perhaps the way the acoustic guitars sounded detailed, yet with an almost creamy midrange? The sound of the guitar pick hitting the strings was clearly audible, as were the drum sticks hitting the cymbals, but in no way did they sound like they were separate events from the sounds of the instruments. Mick's voice was front and center with an eerie life-like presence, and whenever it was doubled or otherwise affected it was apparent that it was done with the utmost appropriateness. This midrange accuracy combined with its mid-bass wallop made each song's timing communicate its message (I guess this is just another way to say that it "rocked?).
I sort of wish this amp had some major shortcomings that I could write about to fill up this review with comments about them. But it didn't. It was a perfect match for the PSBs and the rest of the system, which at the time consisted of a Balanced Audio Technology VK-3i preamp and a Tjoeb 99 CD player. This all-tube system didn't sound rolled off in the highs one bit-it just sweetened the trebles to the point of being a little softer than completely neutral, but never did I feel like I was missing one iota of the musical program.
A CD that I listened to often in this system was Bruckner's Eight Symphony played by the Vienna Philharmonic conducted by Pierre Boulez on DG that I was listening to as preparation for Issue 95's Double Double column. Power orchestral through a pair of PSB speakers? Yes. Although it was missing the deepest bass, the intensity was conveyed through this system more than partially due to its huge soundstage. In addition, the highs of the horns and strings sounded as sweet as can be-and likely how they sounded in real life during the recording session. I dare one person to fault the playing of the Vienna on this CD, and the RM-10 let me hear deep into the recording to check out every nuance of their performance, and of course at the same time never sounded overly detailed. The CD was rendered through the RM-10 with the feature I most admire about any amplifier-to just get out of the way, increase the gain to a sufficient level, and let me enjoy the music.
Nevertheless, I couldn't resist using this amp in the big rig for a while. I think that any shortcomings I heard during these sessions were due to the amp's low power more than anything else. Although it doesn't take much power to drive them, the Sound Labs definitely thrive on a healthy dose of wattage that the RM-10 just can't deliver. Therefore, this amp sounded a bit threadbare in its frequency extremes. I don't want to give the impression that it sounded bad in this system, because it didn't. And judged on its own it was still a quite impressive Basis/Lyra/Tri-Planar analog, Sony/Perpetual Technologies/Monolithic digital, Audible Illusions, Velodyne system. But the system didn't come alive as when using my usual 250-watt Krell KAV-250a amplifier.
The super-transparent Sound Labs revealed what the RM-10 was made of in a way the small PSBs couldn't. In absolute terms the upper most highs were rolled off, and the deepest of the deep bass was hardly present. Again, the subwoofer took care of the bass, but the highs were affected so it made the midrange seem pushed forward in a way I had not noticed before. Yet even with these seemingly major shortcomings I had this amp hooked up to this system for quite some time, and was able to enjoy quite a bit of material through it. I'm exaggerating about its limitations a bit to make my point, too, because its frequency extremes were not truncated nearly as much as one would expect from an amp with this amount of power driving these type of speakers. Heavy metal was out, but if I kept things a bit more conservative I was able to enjoy things quite a bit. Classic Blue Note jazz LPs sounded, er, classic, chamber music sounded as if I was either in the room with the musicians were in the room with me (depending on the recording), most pop and rock, and simpler electronic albums were as captivating as they ever were.
Although the RM-10 really didn't have enough power to drive the Sound Labs, it performed better on these speakers than did the more costly Atma-Sphere S-30. This is likely due to its 4- and 8-ohm speaker taps, so the Music Reference is compatible with more speakers than the S-30. On the other hand, on more efficient speakers the Atma-Sphere sounded more transparent and powerful, so I think the extra money might be worth it if one is willing to live with its challenges of the S-30's large size, heat, and inconvenient input plug locations. But it is surprising how close the diminutive RM-10 comes to sounding as good as the much larger and more expensive S-30.
But I shouldn't spend more time describing the RM-10's sound when it was hooked up in the big rig. It didn't spend enough time there to justify a full review, nor did it belong there. Hooked up to the PSBs, the RM-10 was such a perfect match I could have lived with this system forever. I was that good.
So, back to the Bruckner. For the Double Double column I was pitting it up against Riccardo Chailly's version with his Concertgebouw Orchestra. When performing these listening tests I had no trouble discerning the character of each version. This was in no small part due to the huge soundstage being emitted by the PSBs via the RM-10 that I spoke of. Boulez's with the Vienna sounded more taut and was more powerful in the bass. Chailly's with the Concertgebouw airier account also came through crystal clear. Both of these are fine versions of this symphony, and my preference between them was not immediately apparent on the first listen." it occurred after a while, and a large part of my opinion was formed while listening to it through the PSBs. Even though initial sessions with the two discs took place in the big rig, it was when listening through the very revealing Music Reference/PSB system certain aspects of the interpretations and the sound quality of the discs were quite apparent. I was able to delve into the piece to hone my opinions. No, it didn't have earth trembling bass or huge instrument images, but I was still able to examine the piece without feeling I was missing any of the fine points. And I was able to enjoy these two versions immensely!
One Fine Amp: The Music Reference RM-10 by RAM Labs is one fine amp. I think anyone with a smaller system--especially one using small speakers and a subwoofer couldn't ask for much more. Sure, it gets hot, other equipment can't be stacked on it, and it takes a couple of minutes to warm up. But these are minor flaws in an otherwise near-perfect-sounding amplifier. It is the antithesis of solid-state-sounding in the mids and highs, has a powerful mid-bass, is awfully muscular sounding for its 35-wpc rating, and it looks cool, too. I highly recommend an audition.
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|Date:||Jun 1, 2003|
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