Margules Audio U280-SC Black power amplifier Page 2

Also on the top deck are blue LEDs to indicate the power tubes' bias and operation. These light up only after several minutes, when autobiasing is completed and the U280-SC is ready to be used, and change intensity with the output level. If an LED's illumination remains constant, dims, or is rarely activated, there's likely a problem with the associated tube.

Act I: Where's the Soprano?
The U280-SC Blacks arrived the same day that John Quick and Brad O'Toole of dCS stopped by with review samples of the dCS Vivaldi 2.0 and Network Bridge. As I prepared lunch for our starving fish and dogs, the dCS boys installed the amps. Thank goodness, they removed the foam padding inside each amp's tube cage before firing them up; had they not, our soprano might have sung Brünnhilde's Immolation Scene much too soon. Carlos Smith assures me that at the top of his to-do list is the creation of a printed manual (at present it's available only online), and warning stickers to affix to the cages.


Operation was a snap. Tubed and class-A though they may be, the 67-lb Margules amps omitted less heat, used less power, and were easier to move than my reference monoblocks, the 160-lb, solid-state Pass Labs XA-200.8s.

Other than producing through the tweeters a soft buzz that was inaudible from my listening sweet spot 12' away, the Marguleses operated flawlessly. They'd arrived with only 100 hours of break-in, so between listening sessions I played music or break-in tones.

As my listening began, the U280-SC's "Black" appellation mirrored my mood. The bass sounded anemic and muffled, and the entire sound was hazy and rather gray. None of this stopped the communication of emotion—my sister-in-law was in tears as we listened in DSD to mezzo-soprano Alice Coote sing Mahler's Rückert Lieder, with Marc Albrecht conducting the Netherlands Philharmonic Orchestra (SACD/CD, Pentatone PTC 5186576), but pianist Arcadi Volodos's Brahms (24-bit/96kHz FLAC, Sony Classical 88875130192) sounded, in her words, "like it's behind a heavy, velvet curtain." The sensitivity of Volodos's playing came through loud and clear, but it was impossible to get a true sense of his sound.

Over the years, I've found that manufacturers frequently understate how much break-in their products need. The U280-SC Black's manual says 150 hours; in my experience, 250–350 is more like it. With time, that heavy, velvet curtain lifted to reveal more beauty. Nonetheless, on Jobim and de Moraes's "Insensatez," from Rosa Passos and Ron Carter's Entre Amigos (CD, Chesky JD247), the low-key, seductive vibrancy of her voice was too toned down. In addition, Carter's double bass sounded far too soft, and Luis Galvão's acoustic guitar sounded muffled, as if played with a mute. An especial paradox was the grand piano in Murray Perahia Plays Handel and Scarlatti (CD, Sony Classical 62785), which sounded simultaneously clangy and soft. The air was wonderful, but the body and texture were deficient.

Julian Margules had urged me to experiment with setting both amps to 4 ohms and to Triode mode. Neither improved things. The decreased power output meant that the bass went further AWOL—forget about playing a symphony by Mahler, or by anyone—and piano sound had no meat on its bones. Only when the amplifiers were set to 8 ohms and Ultralinear mode could I hear a semblance of what I'd hoped to hear. But even then, as I scribbled while listening to Mozart's Great Mass in C, K.427, with Masaaki Suzuki conducting the Bach Collegium Japan (SACD/CD, BIS 2171), "the recording sounds beautiful as long as you're willing to sacrifice soprano Carolyn Sampson's winning freshness, and forgo expected depth of soundstage, richness of instrumental color, and transparency."

What to do? I knew that earlier versions of the Margules U280 could sound much, much better than this. Clearly, the amps were a poor match for the Alexias.

So I asked René Jaeger, president of the Pacific Northwest Audio Society, to canvass the group's members to see who had easier-to-drive speakers and was willing to let me swap out their amps for the U280-SC Blacks. I received invitations from two members: Renan Jefferies, with Harbeth M40.1 speakers, and Max Verun, with Sound Lab Millennium 2 speakers. Bless everyone's big hearts for coming to my rescue.

Entr'acte: What We Do for Art
Yours truly lugged two 67-lb amps and, just in case, Nordost Odin 2 interconnects and power cords from his music room to the trunk of his ancient car, and embarked on a three-hour journey that included one ferry ride and a drive across a floating bridge—harrowing for someone with bridge phobia. Having made it across alive, I hauled the amps through Renan's large garage and up two flights of stairs to his lovely listening room. After playing several tracks to get a baseline sound—beautiful depth, natural timbres, rolled off on top, with excess midrange and bass energy—we switched to the U280-SC Blacks.

Act II
Are you familiar with the ecstatic Sonnenaufgang (Sunrise) section of Richard Strauss's Eine Alpensinfonie? That's how I felt when I heard the Margules U280-SC Blacks through speakers friendly to lower-powered tube amplification: Renan's Harbeth M40.1s. With Carolyn Sampson's wonderful recording of Schumann's deceptively simple song "Schneeglöckchen" from her recital disc Fleurs (SACD/CD, BIS 2102), the leading edge of her fresh tone glowed, and Joseph Middleton's piano possessed a natural midrange. True, there was more sibilance than I'm accustomed to, but this was, without a doubt, the Carolyn Sampson I've grown to love.

Even more revelatory were ultra-demanding 24/96 WAV files of the final section of Stravinsky's The Rite of Spring, with Ludovic Morlot conducting the Seattle Symphony (Seattle Symphony Media 1005). Colors were natural and ideally saturated, the top was intact, and the midrange in balance—just what I'm accustomed to hearing through my Alexias. Especially believable were timpani attacks, their sharp edges quickly morphing into resonant decays.

Switching the cables to Nordost Odin 2s delivered more natural body and weight, and a more even distribution of volume and emphasis across the music's multiple octaves. Most important, it made for a far more savage Rite. All I expected from this recording, and all I needed to know about the Margules amps, were there.


During my trips to the other audiophile's homes, there was no need to repeat the process. Hey, I was tired, and I had to find my way back home without recrossing the Bridge from Hell. Instead of auditioning the U280-SC Blacks, we listened, swapped cables, listened again, and had a great time. Maria Callas never got her chance to sing Aida's Triumphal Scene. Wrong opera. This one has a happy ending.

Critical Accolades
As our diva steps forward to thunderous applause, she parts her robes to reveal a glowing tube core. The star is the Margules Audio U280-SC Black. Previously booked in theaters where her gifts couldn't shine, she's now hailed as a full-throated artist with a voice filled with color, and whose interpretations are richly nuanced. Most remarkable are her huge range, thunderous chest tones that rival in power and depth those that any other dramatic soprano can produce, and rapid response to anything composers might throw at her.

With appropriate speakers and settings, the Margules U280-SC Black deserves top billing on select marquees. It's a fine class-A tube amp whose modest power output belies its ability to deliver one winning performance after another.

Margules Group
US: Margules Group USA
Columbus, GA
(888) 538-8605

NeilS's picture

I'm not an engineer, so please excuse if this is a dumb question or I'm misusing terms. This amplifier's total harmonic distortion is stated as 0.08% at 7V RMS. Can the level of THD in an amplifier be converted to an effective bit depth resolution capabilty?

Ortofan's picture

... S/N ratio of 62dB which is equivalent to a resolution of 10 bits.

NeilS's picture

So if you play a 24/192 flac decoded by a 64 bit computer chip and converted by a DAC with 16+ bits of resolution and then sent to an amp with a 62dB S/N ratio (10 bit resolution), what gets sent to the speakers is 62dB (10 bit) resolution?

Ortofan's picture

... a random uncorrelated signal, THD is the sum of signals which are harmonically related to the fundamental tone. If you look at Fig. 16, note that the second harmonic is at about -40dB, the third harmonic at about -55dB, and all higher harmonics are at or below about -70dB.

Compare this with Fig. 9 from the test of the Benchmark AHB2, where all harmonics are below the level of -110dB:

You could argue that the higher level of THD - especially the level of second harmonic distortion - effectively limits or reduces the resolution of the playback system, yet some listeners may find the resultant sound quality preferable:

NeilS's picture

Thank you very much for the explanation. It makes sense that the resolving capability of the system can't exceed its 'lowest-res' component. Another way of looking at the THD in component measurements that I hadn't realized before.

Ortofan's picture

... the Harbeth Monitor 40.2 speakers and a pair of the Audio Research Reference 250 SE amplifiers.

Anton's picture

You know those follow ups where another reviewer compares experiences?

This would seem great to continue to try to wrap my head around this product.

Even the manufacturer is fascinating.

tonykaz's picture

what did the Wilson people have to say?

Wow, the Amp has beautiful engraving, I bet they'll start a trend of using a CNC machine to do this gorgeous chassis decoration. It's kinda like one of those artistic Tattoos we occasionally see.

It's a Beautiful Amp, I'd like it to be a success.

Some of this Company's other offerings are also beautiful.

Tony in Michigan

pma's picture

This amp has high output impedance and the frequency response will be strongly modulated by speaker impedance plot, as we can see in

This will be audible with most speaker, so we have an example of another effect box here, rather than an amplifier.

Anton's picture

I hadn't thought of the term 'effect box,' you said it well.

johnnythunder's picture

Obviously, something that deviates from absolute clinical technical perfection with no horrifying overtones or those terrible euphonic colorations. Definition of euphony:
1 :pleasing or sweet sound; especially :the acoustic effect produced by words so formed or combined as to please the ear
2 :a harmonious succession of words having a pleasing sound

Terrible things those amplifiers or source components that make pleasing sounds. Oh wait we cant call them truly amplifiers because they may make music sound pleasing to the ear. That's not what music is supposed to do.

pma's picture

Is the SET distorted sound still 'pleasing' when playing complex philharmonic orchestra, Beethoven, Mahler? Do we want a modified sound or true reproduction of the recorded sound?

Ortofan's picture

... was asking the very same question 30 years ago.
"Should an amplifier be pleasant sounding, or should it be accurate even if accuracy is not as pleasant?"
See the next to last paragraph:

pma's picture

Well, the question put this way is no good. Well designed and engineered amplifier is never "unpleasant sounding", in case you have good speakers, good listening room, good recordings and good signal source. If someone listens to commercial music only, I agree it is a pain since pocket audio started with iPod in 2001 (thank you, Steve) and huge dynamic compression took place almost everywhere (sounds good in subway for millions, right?). But with good classical recordings, good speakers and listening room, good DAC, the accurate amp never sounds boring or unpleasant. Please find a real fault in other parts of the audio chain.

Ortofan's picture

"Not as pleasant" is not the same as "unpleasant."
Also read the op-ed piece from AD linked above.