Solid State Power Amp Reviews

Edmund (Ed) Manfred Meitner's name and reputation have long been synonymous with pioneering achievements in the fields of digital audio, especially DSD. In 1971, after designing the first fully automated studio console, Ed identified what he calls "the jitter problem." He worked with Sony and Philips to help create and refine SACD and subsequently designed the first complete six-channel DSD playback system for home use.

In 1998, while developing the eight-channel A/D and D/A DSD converters still used to create most SACDs, Ed founded EMM Labs (footnote 1) and became head of design, with the goal of bringing DSD to the consumer realm. Far more recently, he designed the EMM Labs DS-EQ1 and Meitner DS-EQ2 optical equalizers, which are sanctioned by DS Audio for use with their optical cartridges.

Less widely discussed are Ed's amplifier circuit designs, which are the heart of the EMM Labs MTRX and MTRS amplifiers he designed collaboratively with Mariusz Pawlicki, EMM manager of R&D, and the late Zenon "Zanny" Muzyka. Mariusz helped develop the operating scheme for the amplifiers, the "smarts" in the amplifiers' monitoring and protection schemes, and their new "hybrid" power supplies. (More on this below.) He is also actively involved in quality control (QC) and measures every amplifier that leaves EMM Labs. Zanny, who passed before completion of EMM's latest amplifier designs, contributed to their industrial design and power supply.

EMM Labs' history producing amplifiers dates back to 2012, when it released the original 1500W class-AB MTRX mono amplifier ($130,000/pair). The company has since released various upgrades, including those to the driver/input stage. In 2015, EMM released the 1000W MTRX2. Most recently, in November 2023, EMM announced its successor, the 1000W MTRX2 V2 monoblock ($115,000/pair), as well as the MTRS ($65,000), the company's first-ever stereo, class-AB power amplifier and the subject of this review.

The new MTRS
The brochure for EMM's first stereo amplifier states that the MTRS, with its 400Wpc peak power into 4 ohms, "is able to drive the most severe loads with no overall feedback, using Ed's completely redesigned high current Meitner Power Driver. The MTRS can handle any speaker load with ease, delivering high power, low distortion, and wide bandwidth" (footnote 2). The MTRS also incorporates a new, proprietary power system, fully discrete circuits, fully balanced audio paths throughout, custom ceramic PCB boards, and real-time protection to avoid speaker and amplifier damage.

Save for specifications, the website provides very little additional information—so, shortly before deadline, in an attempt to glean more information, I participated in a Zoom conversation with Ed, Mariusz, EMM COO Amadeus (Deus) Meitner (who is also Ed's son), and Director of Sales and Marketing Shahin Al Rashid. Because Ed was recovering from surgery, the conversation was brief. Additional details arrived by email from Deus and Mariusz.

"Everyone else on the design team came up with the idea of the MTRS, because I never in my wildest dreams imagined making a stereo amp," Ed said as he threw the first of several monkey wrenches into our chat. "I think it's the wrong way to build amplifiers. You wonder about interference from left and right channels, and you compromise the whole situation by putting it all in one box. It's kind of stupid. Stereo amps are common, and maybe people like them better. They're just not my dream for proper setup." Having interviewed Ed before—his son frequently calls him "a lovable pain in the ass" to his face—I smiled, chuckled inside, and waited to see how everyone would maneuver around the landmine that the amp's own circuit designer had placed in our path.

Deus attempted to defuse. He noted that the size and weight of EMM's big monoblocks is hardly ideal for apartments in Singapore and Hong Kong. The same holds true for small flats in London, or anywhere with insufficient power to run those big boys. For many people, a stereo or integrated amplifier is the way to go. Perhaps the only way.

"The transformers we used in our original MTRX mono amplifiers are no longer available," he added. Obsolescence is an opportunity for improvement. "Now we have an altogether new power scheme that, together with a new input stage and management system, is much better. The new technology is a big step up from the original design, and all of it is fully incorporated into the MTRS stereo amp."

Even Ed seemed to backpedal a little bit, offering faint praise for this Ed Meitner stereo amplifier. "We've made sure the MTRS is reliable and won't set things on fire," he said (footnote 3). "In all the years we've had our 1.5kW amplifiers, we've never had a problem." And then he went further. "Ultimately, I'm reasonably satisfied with what we've accomplished with this stereo amplifier. If I weren't, it wouldn't go out the door."

After Deus described Mariusz's amplifier management system as "smart," with "quite a lot of brains in it," its designer spoke up. "The MTRX/S internal supervision system, aka State Control & Measurement system, checks multiple test points. Under no circumstance can it exceed the normal, safe, predefined operating envelope. It's protected from user errors, internal manufacturing errors, shorts, and overloads. It won't blow up speakers or take out tweeters."

The MTRS hybrid power system includes three newly designed toroidal transformers: two power the left and right output stages, and the third powers the lower voltage "stuff." In addition, there's a separate switch-mode power supply that powers the input stage. Deus describes the input stage, which was finalized after close to 40 iterations, as "the secret sauce" for the amplifier's sound.

Before signing off on the MTRS, the design team replicated every test that John Atkinson performs on amplifiers, using the same test equipment. "We addressed the 50Hz and 60Hz noise that was vibrating the transformers," Ed said. "That noise is a real pain in the butt."

Ed the contrarian next expressed his aversion to voicing and tweaking, insisting instead on the primacy of measurements. "The measurements should be the absolute first thing," he declared. "What decides the sound? If you compare two amplifiers on the same speakers, there's a huge discrepancy in the interaction between the amps and the load of your speakers. Sound has to meet the measurement criteria. Without the measurements, there is no 'sound.'"

Nonetheless, after the MTRS (or other EMM product) reaches what Deus calls "our threshold for measurement 'hygiene,'" its circuits do get tuned. "We continue to work on the circuits with a combination of objective and subjective analysis until we reach our goal," he said. "That's why we created so many versions of the input stage before we were satisfied. Ed has always said that he is not in the music business; he is in the sound business. So, the idea of 'tuning' is open to interpretation."

"In Ed's designs, the objective part always comes first," Mariusz clarified. "It's a kind of guarantee, because very high performance on measurements will lead, eventually, or very soon, to the sound."

Can it or can't it?
The EMM website says that the MTRS, with a peak output power of 400Wpc into 4 ohms, can drive even the most severe speaker loads, down to 1 ohm. Ed, though, was ... less certain. "The speakers you have there—the Wilson Alexia Vs—are relatively inefficient," he said. "That poor amplifier is suffering. It's not compatible."

Just as I began to wonder if I should have waited to review the 1000W MTRX2 V2 monoblocks, even if they wouldn't be available for a while (footnote 4), Mariusz attempted another quick save. "The definitive feature of all MTRX/S amplifiers is their ability to drive with ease 'difficult' loads, i.e., speaker systems with complex impedances and very low overall impedance," he insisted. "In extreme testing, they can drive 1 ohm loads with aplomb, delivering all the power required while maintaining very low levels of distortion. This stereo amp is not afraid of 1 ohm loads at all (footnote 5).

"Under normal operating conditions, any MTRX/S amplifier will maintain low distortion levels across the entire audio spectrum. Even the distortion of a 20kHz signal at full power (which does not happen with real-life music programs) is very low. This guarantees perfect music reproduction at a very high output, which is what MTRX/S amps aim for."

There was only one way to find out. Actually, since the interview took place after I'd already done a fair amount of listening, I already knew.

Front, back, and beyond
The MTRS's "Standby/Power-Save" button is positioned inconspicuously to the right of the "EMM Labs" logo in the amplifier's black center panel. When you press it, the MTRS goes through a 5–10 second safety-check sequence before enabling full power. Under the front of the center panel, an indicator light switches from red to blue. Reflected from my stained bamboo floor, the light appeared to transition from orange to purple. Whatever the color, the illumination was unobtrusive. If it's still too bright for you, there's an "indicators off " option.

The left quarter of the rear panel contains three different logos, a "Model / Serial" plate, and an RS-232 Communication Port for diagnostics and firmware upgrades. In the larger, middle section, pairs of RCA and XLR inputs and speaker cable outputs are intelligently spaced to prevent cable crossing. The locking, easily adjusted Furutech speaker-cable connectors are a dream, clicking when connections are secure. On the top right of the rear panel sits the "main power breaker." Below is the round, 30A, 250V, three-pin, IP44, IEC 60309–type "Power Inlet," which holds the specially terminated Kimber Kable PK10 Ascent PowerKord supplied with the amplifier.

The MTRS is too big for my amplifier stands, and its attached feet are too deep to engage the neutral-sounding Wilson Audio Pedestals. Hence, with more than "a little heave-ho / don't let my lower back go," onto the floor it went.

The power cable
I'd previously auditioned Kimber Kable power cables and knew that the top-level PK10 Palladian PowerKord would deliver noticeably more bass and body than the supplied midlevel PK10 Ascent. Because my reference cabling is all top-level Nordost and AudioQuest, I felt it only fair to use Kimber's top-level cord. To give the MTRS its best opportunity to shine, EMM Labs and Kimber kindly supplied me with both the PK10 Ascent and the PK10 Palladian.

For most of my listening, I stuck with the top-level. Whether this was the wisest choice was a question I began to ponder in the weeks ahead.

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Footnote 1: Ed Meitner's original amplifier designs were the MuseaTex STR55 stereo MTR101 mono amplifiers, which he created decades ago. See stereophile.com/content/ed-meitner-audio-maverick.

Footnote 2: See, eg, emmlabs.com/images/products/manuals/MTRS_Manual_V1.1.pdf.

Footnote 3: As a former beta tester for another company and product type who once witnessed a thankfully short-lived 18"-high burst of fire and cloud of acrid smoke fill my living room, I can well appreciate Ed's care and concern.

Footnote 4: God and Jim Austin willing, I'd still love to review them down the line.

Footnote 5: Wilson Audio claims the Alexia V's impedance dips to 2.59 ohms at 84Hz; John Atkinson measured 2.45 ohms at 85Hz. Wilson specifies the Alexia V's sensitivity as 90dB/W/m; John estimated 88.8dB/W/m. John also said the electrical phase angle is high at low frequencies and effective resistance (EPDR) drops below 2 ohms between 50Hz and 90Hz, hitting a minimum of 1.15 ohms at 66Hz. Hence, the Alexia V "needs to be matched with amplifiers that won't be fazed by low impedances," JA concluded.