October 2023

World Premiere Review!
Margules Audio U-280SC 30th Anniversary Limited Edition Vacuum Tube Amplifier Review
Realistic sound with extended frequency extension... plus tube rollers can rejoice too!
Review By Tom Lyle

  Margules Audio is a high-end audio company that produces a full line of components. It is headquartered in Mexico City, Mexico, and although the Margules Audio U-280SC 30th Anniversary Limited Edition vacuum tube stereo amplifier review you're about to read is brand new, the company has been in business since the early 1980s. The Margules family – now including third and fourth-generation members – has been involved in audio in one way or another since the early part of the twentieth century, when Mr. Jacob Margules, a European engineer. He also contributed to the building of radio stations and electrification in Mexico as they manufactured wind-up gramophones, followed by tube radios, plus they distributed industrial parts too.

Class A
The Margules U-280SC 30th Anniversary tube amp is a vacuum-tube amplifier that operates in full Class A and has an output power of 50 Watts per channel when used in ultra-linear mode and 25 Watts per channel in triode mode. One can easily switch between ultra-linear and triode by flicking a switch on its top plate. Switching between triode and ultralinear mode can even be done while the amp is playing music, on the fly, so the user can change it to see which is the preferred mode for a given recording.

This Margules amplifier uses a proprietary auto-biasing circuit they call "Active Servo Bias." The amp requires no polarization adjustments and allows the amp to operate continuously in full Class A, with zero negative feedback.

It also makes it so the amp's circuit can be powered with not only the supplied KT88 power tubes, but if the user wishes to do so, KT-90, KT-120, KT-150, and 6550 tubes without any adjustments. The active servo control manages the bias and works in real-time, set by the signal, not by the tubes, making the amp always operate in Class A. It also is claimed to "radically" extend the life of its output tubes and "optimizes energy consumption by avoiding overheating."

Power
Those who have read some of my other reviews know I often stress the importance of a suitable power supply. The designers of this amp obviously agree. In their U-280SC 30th Anniversary tube amp, Margules uses a shunt-regulated power supply. It minimizes current variation even if the load fluctuates. Their literature (their website) also claims that the amp's power supply has a "carefully designed circuit" that does not include a control loop circuit. I discovered that a control loop requires high gain and wide bandwidth to achieve good regulation and rapid response to sudden changes in its load. Control loop gain will more than likely limit bandwidth, and by not having it, this avoids the triggering of unwanted harmonics. In other words, this makes the music signal from this Margules amp sound good!

I could easily use all allocated space in Enjoy the Music.com‘s server if I were to describe all the technological innovations used in this amplifier. But this review wouldn't be complete if I didn't touch upon a few of its critical technical features.

The Margules Audio U-280SC 30th Anniversary Limited Edition vacuum tube stereo amplifier avoids using negative feedback, which they say causes a loss of detail and "sound richness." But Margules compensates for the commonly used negative feedback, so they developed their "Back Electromotive Force Sensor System," or BEFS, which changes a common practice that results in a loss of detail and "sound richness." The BEFS improves the damping factor without resorting to negative feedback. They go on to say that the BEFS, combined with their Active Servo Bias, allow the amp to drive one's speakers "with excellent dynamics and controlled bass," which they say can be the most demanding loads in low-efficiency or speakers with low sensitivity.

Even though this amplifier only has one stereo input, it can legitimately be called an integrated amplifier because of its input attenuator (volume control). This amplifier is also bridgeable, so it can be switched from stereo to mono operation so they can be used as monoblocks. When used as a monoblock, the amp doubles its output power and, of course, increases stereo separation.

ANA Technology
Lastly, I should mention what Margules considers one of their most important technological innovations. So, I'll paraphrase some excerpts from a white paper written by Julian Margules:

Margules' technical design philosophy, ANA (Aligned Neuro-Acoustics), resulted from an analysis of how people perceive sound and the desire to understand the difference between what is measured and how it is perceived, in other words, how it sounds.

The guiding principle of ANA was to create a technology that could produce a component with excellent sound quality that generated a link between the source of the sound and the listener. "ANA creates sonic characteristics based on the meticulous care of the harmonic structure, not on the fundamental tone."

Margules believes that the age-old methods of measuring audio equipment shouldn't be relied upon as much as they are. They have little relevance to the results that come from listening tests. The sound's harmonic structure is much more important, resulting in a characteristic that should be given much greater relevance: engagement.

According to Margules, an engaging sound is "directly linked to our primary survival instinct," which pays most attention to nearby sounds rather than distant or of minor importance. An engaging sound demands our attention and retains it. Its counterpart is a sound that is muddy or insignificant.

"ANA technology is designed to achieve a realistic sound, with a wide frequency response, low distortion and precise harmonic reproduction, optimizing to the utmost the relationship between the source and the receiver."

Although it did not say this in Julian Margules paper, I assume that ANA is performed chiefly during listening tests since our ears are our best-measuring device for these types of sonic characteristics.

Amplifier
I used the Margules U-280SC 30th Anniversary amplifier in my second system, which is more accepting of lower-powered amplifiers. My main system is in a dedicated listening room where I use electrostatic speakers that require a solid-state amp with a minimum power of over 200 Watts per channel. The second system is in our dining/living room, which uses more efficient speakers and is closer to a space where most listeners' stereo systems are found.

At first, I had the Margules amp connected to a pair of Scansonic MB5 B speakers because I recently reviewed them in Enjoy The Music. Since they were reaching the end of their loan agreement, they were due back to their distributor only a short time into the Margules amplifier's review period.

The remaining portion of the audition was spent with the Margules U-280SC 30th Anniversary tube amplifier connected to a pair of Enjoy the Music.com's Best of 2023 Award-winning Vermouth Sound Monitors. These speakers use two 6" mid/woofers and a ribbon tweeter arranged in a D'Appolito configuration (the tweeter is located between the two woofers). These $20,000 loudspeakers aren't as small as their name may imply. They stand nearly 2 feet tall, about 0.5 feet wide, and slightly more than 1.5 feet deep.  

I used a single subwoofer during my relatively short time with the Scansonic speakers in this system — I used an SVS SB-2000 to boost the lowest bass frequencies. I kept the subwoofer's volume quite low, mainly because these speakers didn't need that much augmentation in their bass frequencies. Surprisingly, I didn't need to use the subwoofer at all when using the Vermouth Studio Monitor speakers.

Even though their manual states that the lowest bass frequencies of the Vermouth speakers reach down "only" to the 30 Hz range, still no sub was needed. Without a sub, all the bass frequencies I heard in my room were the responsibility of the Vermouth speakers via the signal coming from the Margules amplifier.

The analog source of this system is built around the highly excellent for the price Pro-Ject X2 turntable. This system may deserve a more sophisticated player. But almost immediately after acquiring this 'table, I replaced its stock $300 Sumiko Moonstone moving magnet phono cartridge with a moving coil cartridge. At first, I used a Lyra Kleos, and a short time later, I mounted an Ortofon MC Winfield Ti phono cartridge onto its integral tonearm. The resulting sound was mighty, especially since I connected the turntable's pair interconnects to a Pass Laboratories XP-17 phono preamplifier.

The digital front-end of this system included an Oppo BDP-83 Special Edition universal disc player and occasionally an Oppo BDP-203 Blu-ray / universal disc player. I listened to these players only occasionally. More often I could be found listening to either Tidal or Qobuz streaming services through a Cambridge Audio streamer with its digital output connected to an Audio Analogue aaDAC, a digital-to-audio converter made by the Italian high-end audio manufacturer Audio Analogue. This DAC also has an aptX Bluetooth receiver with excellent sound quality when streaming via Tidal or Qobuz. Listening while controlling Tidal or Qobuz from my iPhone or iPad was the epitome of convenience.

Even though they were connected to the Margules amp for a relatively brief time, listening to the Margules amp while connected to the Scansonic MB5 B speakers proved to be a very enjoyable experience. Plus, these speakers were good enough to let me hear that the Margules amplifier was a fine one! Despite the Scansonic speakers having four 5.25" woofer/midrange drivers and a ribbon tweeter while reaching about 3.75 feet off the floor, their sensitivity was more than acceptable 90dB/W/m. Even during this short time, they were paired together, it was clear that the Margules/Scansonic combination was a good one.

Volume
I learned that even in ultra-linear mode, this amplifier could easily drive the Scansonic speakers to a volume that I considered "realistic." Not only was the volume more than satisfactory but so was their sound, due to the sound quality prowess of the Margules U-280SC 30th Anniversary tube amplifier. Even though the Scansonic MB5 B speakers cost less than half the price of the speakers that were used for the majority of the audition period, their midrange transparency made it so I felt as if I could hear not only details from the musical signal being sent to the speakers but the details from the musical signal that was sent to the Margules amplifier.

The above description might seem a bit obtuse. Yet, it was the relative amount of transparency of these speakers that led to a feeling that I could imagine hearing through to the Margules amp, and therefore could sense that I could clearly hear the intentions of the musicians, engineers, and producers that were responsible for the recording I was listening to at the time. The Margules amp's level of transparency was often frighteningly lifelike sounding on some recordings.

The Margules amplifier sounded neither audibly tube-like nor solid-state-like. What I heard coming from this amp was music. This amplifier gave me the feeling that I was hearing a very accurate version of the recording, but without any of the amp's own sonic signature that would compel me not to think, "What a great sounding amplifier," but rather, "What a great piece of music!"

With the Vermouth Audio Studio Monitors in the system, this is when the sonic magic really happened. The Vermouth Audio speakers were closer to what the average Margules customer might have as part of their audio system. The Margules amp proved itself to be an incredible-sounding power amplifier when listening through these speakers.

Lately, I've been getting into the mid to late-1960s Wayne Shorter albums on Blue Note Records. Shorter was not only an excellent tenor saxophonist but also an excellent band leader, at least good enough to be able to have a good band behind him, with members often hailing from either John Coltrane's band, such as drummer Elvin Jones and bassist Reggie Workman, or future bandmates in the Miles Davis Quintet such as pianist Herbie Hancock and bassist Ron Carter. On his other appearances on Blue Note as a leader, Wayne Shorter also surrounded himself with excellent horn players such as trumpet players Lee Morgan and Freddie Hubbard, trombonist Curtis Fuller, and others.

I played the Wayne Shorter album Speak No Evil multiple times during the audition period. For this session on Blue Note, it features John Coltrane's choice of drummer for several of his albums, Elvin Jones. On "Speak No Evel" also features pianist Herbie Hancock and bassist Ron Carte, who appear on many Miles Davis albums. Speak No Evil was recorded in 1964, the first year Wayne Shorter was a member of Miles Davis' new Quintet. From the outside looking in, these guys kept very busy!

Many regard Speak No Evil as Shorter's best LP. It contains Wayne Shorter's best compositions and some killer improvisation from everyone who was in the recording studio that day. The Margules U-280SC 30th Anniversary tube amplifier let me hear deep into the grooves of this hard-bop / post-bop masterpiece. When I streamed the 24-bit/192kHz version over Qobuz, I felt like a fly on the wall of Rudy Van Gelder's studio. As each musician took their turn soloing, in my mind's ear I was often able to sonically peer into the studio to witness these magnificent musicians at their best.

I did it again. Some might think I spent as much time discussing the music I played through this component as the component itself. But trust me, I've heard many tube (and solid-state) amps powering the speakers in my second system. I have heard only a few that sounded anywhere near as good as this Margules tube amplifier. The amplifiers that sounded better also happen to cost much more, and at $12,000, this Margules amplifier is solid proof that one does not necessarily need to spend a penny more.

This amp's performance in my system was so good I have no problem calling it the paradigm of what a vacuum-tube-powered amplifier should sound like. During its audition period, I listened to many genres through the Margules U-280SC 30th Anniversary power amplifier, including some very aggressive stuff such as heavy metal from all eras and industrial rock from the 1990s.

Nothing could slip this amp up. It regained its composure during the loudest musical climaxes. It could reproduce a whisper of sound regardless of how loud the other instruments played. The Margules amp possessed a feature that I call Dynamic Distance, which is when a component can separate instruments, voices, and sounds occupying the same space in the soundstage playing at the same volume.

During the audition period, I used both its triode and ultra-linear modes, which were switchable with the flick of, er, a switch. Both modes sounded marvelous, and I can't say which I preferred, although when playing smaller jazz and classical ensembles triode was my mode of choice. That the amp delivered less power wasn't as noticeable as I thought it would be, but in triode I was able to "see" into the recording a bit more, the soundstage was wider, and microdynamics seemed to be enhanced. Again, the difference wasn't as great as I would have expected, nor could I find fault with either.

While the Margules U-280SC was in my system, it excelled in every audiophile category I could think of - the size and scale of its soundstage, its pinpoint and realistic sounding imaging, its very extended frequency extension, its convincing micro- and macro-dynamics, and excelled at any other audiophile characteristic I can think of. As a bonus, this Margules amp looked very good, too. Its exemplary fit and finish demonstrated Margules' attention to construction detail.

This amp's ability to satisfy tube rollers is also a bonus. I'm all for trying out different brands and vintages of tubes, but I'm not particularly eager to second-guess a designer's first choice in the type of tube used. The KT-88 tubes that arrived with the Margules amp were obviously high quality, or Margules wouldn't use them. None of the tubes made a peep during the audition period, so there was no sound coming out of this amp other than music the entire time it was in my system.

Choose
I would have nothing negative to say about audiophiles who choose the Margules U-280SC 30th Anniversary Limited Edition vacuum tube amplifier as part of their audio system. This is a compliment that I wish I could say about an amplifier that costs less than the $12,000 asking price of this amplifier (welcome to the high-end). But sometimes one gets what they pay for, and the Margules U-280SC 30th Anniversary Ltd. Ed. amplifier is one of them.

Specifications
Type: Vacuum tube amplifier
Output Power: Triode stereo @ 25 Watts per channel, Ultra-Linear stereo @ 50 Watts per channel, Triode mono @ 55 Watts, and Ultra-Linear mono @ 100 Watts
Frequency Response: 20Hz to 40kHz (-3dB)
Vacuum Tubes: Four KT88 (also accepts 6550, KT90, KT120, and KT150)
                      Plus four 12AU7
Total Harmonic Distortion (THD): >0.08%
Dimensions: 22 x 45 x 35cm (HxWxD) 
Weight: 67 lbs.
Warranty: Five years limited manufacturer warranty on parts and labor
              45 days on the vacuum tubes
Price: $12,000

Manufacturer
Margules Group
Mexico City, Mexico

Voice: (706) 575-0926
E-mail: info@Margules.com 
Website: Margules.com

United States Of America Distributor:
AV Luxury Group International
6738 West Sunset Road
Suite 160
Las Vegas, NV 89118

Voice: (866) 528-8085
E-mail: bruce@avluxint.com 
Website: AVLuxurygroup.com