Note: for the full suite of measurements from the SoundStage! Audio-Electronics Lab, click here.

Say it with me: Are-moh-NEE-uh. Handcrafted by Ars-Sonum, the Armonía ($5250, all prices in USD) is the boutique Spanish audio company’s first power-amplifier offering. It’s a stereo power amplifier based on the company’s Filarmonía SM integrated amp. Spain is probably not the first country that comes to mind when discussing boutique stereo tube amplification; nor is Ars-Sonum the first company name to roll off the tongue—if you’ve even heard of them, that is. This small outfit produces just a few hundred amplifiers per year, lovingly hand-assembled at Ars-Sonum’s facility in Madrid. Though such boutique manufacturers often aren’t afforded the space or resources—or economies of scale—that larger manufacturers leverage to pump out appealing products at affordable prices, they tend to have a considerable amount of freedom to build truly unique and outstanding products. Ars-Sonum is no different, and the Armonía is a premium tube power amplifier, designed for sound quality above all else, that reflects this reality.

Hecho en España

Standing about 7.5″H from the bottom of its three chunky rubber feet to the top of the power transformer and just over 14″W × 10″D, the Armonía shares its flashy, chromed stainless-steel chassis with the Filarmonía. In fact, it has much in common with its integrated amplifier sibling, including the all-important tube complement: a gold-pin JJ Electronics E88CC input tube is mated to a pair of Philips JAN 5814A tubes, each of which functions as the driver and phase-inverter stages for its respective channel. Two pairs of JJ E34L pentodes—not to be confused with the far more common EL34—make up the output stage. Ars-Sonum says that the tubes are hand-matched with only around a quarter of tubes testing well enough to make it into one of these amps. In fact, ultraprecise hand-matching is a crucial part of the Armonía’s construction. Not only are the output tubes matched to within 2% of each other, the other components in the output stage are matched to less than 1%. Special mention should be made of the output transformers and cathode resistors, which are matched to an even tighter 0.5%.

The output transformers are perhaps the single biggest difference between the Armonía and the Filarmonía. All of the transformers used in Ars-Sonum products are constructed by hand to the company’s design specifications, but those in the Armonía are physically larger, heavier, and even more meticulously constructed than those used in the integrated amp. This is said to improve the power amplifier’s bandwidth at both frequency extremes, as well as to provide slightly improved damping, distortion, and power specs. The overall result, the company claims, is a more harmonious interface with the load presented by the loudspeaker. The improved transformers also explain why, despite lacking the Filarmonía’s source-switching capability and Alps Alpine volume control, the upmarket Armonía costs a bit more than its integrated hermano.

The E88CC tube at the input is coupled to the driver/phase inverter stage via V-Cap CuTF copper-foil and Teflon capacitors, while Mundorf Supreme SilverGold.Oil caps carry the signal to the E34L output tubes. The input and driver/phase inverter stages both make use of matched metal-film resistors. The power supply is constructed to an equally high standard, and comprises five separate sections, with “four of them independently stabilized for each channel and stage,” according to Ars-Sonum. The power supply uses Wima film capacitors along with the more conventional electrolytics, and the power resistors are matched and overspecified to ensure reliability and longevity.

If you’re already into high-end tube amplifiers, this sort of attention to detail is typical, or even expected. What sets the Armonía apart is the utilization of screen-grid regulation for the E34L pentode output tubes. The screen circuit is of particular importance to tube-amp audiophiles, even those with no knowledge or interest in the technical workings of their amps, as it often describes the kind of behavior that can be expected during listening. Traditionally, the screen is supplied with a DC voltage directly from the power supply, though ultralinear amplifiers supply the screen via a tap on the output transformer. Amplifiers that operate tetrodes or pentodes in so-called triode mode tie the plate and the screen together so that the tubes mimic their three-electrode brethren. Regulating the screen supply, as in the Armonía, is a bit off the beaten path as far as tube amp designs go.

The benefits of screen-grid regulation are several, at least in theory. The screen voltage is partly responsible for setting the operating conditions of the tube, so preventing this voltage from wandering up or down as the tube conducts current removes a source of harmonic distortion. Additionally, by stabilizing the tube’s operation, the screen regulation can help to maximize the class-A headroom—a feature of the Armonía that Ars-Sonum is proud of. Finally, asking too much of the screen grid is often a cause of premature death in pentode output tubes, so regulating the screen supply is as much a longevity-minded consideration as it is a sonic one. This is why Ars-Sonum has selected JJ E34L tubes, and why it so ardently discourages tube rolling—the optimum operation and voicing is already achieved by the amp’s design.

Ars-Sonum claims an output of 30Wpc into 8 ohms, an SNR of better than 90dB, a frequency response of 5Hz–30kHz, and THD at 0.4%. It should be noted that the THD spec is measured at 20W, rather than at full power. This may be intended to reflect how the Armonía behaves during real-world use, especially as Ars-Sonum states that the better part of its 30W of output is class A. These are actually rather impressive specs for a tube amp with such a simple design and so few active devices.

System integration

Integrating a power amp into a typical stereo system carries the expectation of being a rather straightforward process, and the Ars-Sonum Armonía doesn’t break the mold in this respect. There are the usual RCA jacks that accept the output of a preamplifier, though in line with the typical Ars-Sonum opulence, we find two pairs instead of one. One set of RCA connections is a high-level input, and the other is low level. This ensures compatibility with preamps of different gain levels. Somewhat frustratingly, they are only labeled Line 1 and Line 2, so it’s not immediately obvious which is which, though trying both inputs makes it quickly apparent. Here’s where I ran into the first of what would be many system-matching lessons: my go-to preamp is a DIY affair called Wayne’s Burning Amp 2018 Line Stage. Named for its designer, Pass Labs’ small-signal guru Wayne Colburn, and the 2018 Burning Amp Fest where he debuted the design, it has 12dB of gain—a rather average number for a solid-state preamp. And with the Armonía’s set of high-gain inputs (Line 1), it was LOUD, even with the volume turned down low. The set of low-gain inputs was much more suitable, though I think even those provided a touch more gain than I’m used to. This opens the door to some interesting matching options, but closes the door on others. I’ll touch on this in greater detail later.

Hooking up speakers is a similarly simple-but-quirky task, as the Armonía makes use of some rather large, solid-copper Cardas connectors that are really only intended to be used with spade lugs. The positive and negative leads are connected, and then the big center knob screws down to secure them. Alas, I am a stubborn purist, and prefer bare-wire connections—this works, but I don’t really recommend it. Regardless, that’s how I hooked up my favorite tube-amp speaker cable—the orange-and-black twisted Belden 9497—to connect the Ars-Sonum to my speakers.

The speakers themselves are the final piece of the equation, as they form the load on the amplifier. Ars-Sonum says it designed the output transformers for optimal performance into a 6-ohm load, so that power output and distortion are not substantially compromised if 4-ohm or 8-ohm speakers are used. Thus, the Armonía isn’t too picky when it comes to loudspeaker compatibility, which is refreshing, though the manufacturer does stipulate that the impedance of the speakers should not dip below 3 ohms. A reasonable demand, to be sure, though plenty of fours and even some eights may drop down that low, so it’s something to watch out for. Finally, Ars-Sonum recommends loudspeakers with a sensitivity rating of 90dB or higher for maximum dynamic realism, though the amp won’t complain even if the sensitivity is substantially lower.

I streamed from Spotify via my LG C1 TV, which I connected to my S.M.S.L D300 DAC through a Monster TosLink Cable. My analog source was my Micro Seiki DQ-3 turntable outfitted with an MA-707 tonearm, also from Micro Seiki. At the business end of the arm resided an Audio-Technica AT95 cartridge with a nude Shibata stylus, or a Sumiko Blue Point No. 3 Low Output. The phono preamps I used will be mentioned in the next section. To complete my system, I used Canare and Belden cables as interconnects. Rich, my contact at Signature Sound, the only North American distributor for Ars-Sonum, says he typically sells the amp with a Cardas Audio Clear power cord ($750 for a 1m length) or an Audience forte f3 power cord ($160 for 1.25m). Rich gave me one of each to try, though I wound up using a generic heavy-duty power cord, partly to keep my evaluation to the basic package but also because it was a more convenient length for my setup.

Escuchando a la Armonía

The listening experience reflected the Armonía’s design and build quality in many ways, but also challenged several of my expectations. I received the review sample in late 2022, and it took me some time to get a tune out of the Spanish power amp in my system. Getting the performance I expected from the Armonía was a struggle: first, I had to sort out a hum issue, which apparently was related to a ground loop involving my DAC and preamp; then I quickly realized that the amp was very sensitive to the equipment it was paired with and the program material it was fed. After weeks of trial-and-error to integrate the amp in my system, I was finally ready to listen critically.

The first characteristic of the Ars-Sonum Armonía that struck me was that of tonal density—a fully fleshed texture to each voice and instrument it reproduces. I noticed this not so much with music, but rather with television. I’d been binge-watching Breaking Bad on Netflix. It’s a fantastic show, and the story has kept me right up on the edge of my seat, but the dialog and sound design are worth a commendation, too. In the episode “Sunset,” Jesse, Skinny Pete, and Badger discuss going into business together, and each of their voices had a weight and texture to them through the Armonía that just isn’t present when using solid-state amplification. The acoustic space of the plaster-walled, nearly empty room where the three men were talking was well conveyed, too. These sonic traits were clear again later in the episode’s tense standoff scene in the RV between Walt, Jesse, and Hank. Walt’s whispers to Jesse and Hank’s muffled shouts coming from the outside of the RV both seemed a bit heavier and raspier than I would’ve expected.

The incidental sounds and Foley effects of Breaking Bad can be pretty great, too, as they serve to further immerse the viewer in the world the show creates. I’ve always found Netflix’s 5.1-to-stereo fold-down to be more than adequate, providing a satisfying “in the room” effect from just two speakers, and the Armonía was up to the task. The amp did a thorough job of creating the illusion of space, with sounds of passing cars, rustling papers, movements of the characters, and the like all emerging from above and around the speakers. Such sounds had a good—but not jaw-dropping—sense of depth and motion as they moved across the soundstage in concert with the images on the screen. Sharp transients and dynamics were not negotiated quite as well as spatial cues, though I don’t feel that the Armonía was lacking in this regard—and maybe it could excel with a pair of more sensitive loudspeakers.

Of course, most Armonía owners won’t use the amp as part of a home-theater system, but rather for serious music listening. Switching to music as the source material, I started with Chon’s self-titled 2019 album (LP, Sumerian Records). Almost right away, I learned how picky the Armonía could be regarding the equipment it’s paired with. At the time, I had just finished my review of the Lehmannaudio Decade Jubilee phono preamp and it was still in my system, so I used it to play the album through the Armonía. Neither component could ever be accused of sounding too bright, but the music sounded dull and lifeless with the Decade Jubilee and the Armonía together, despite each piece’s individual tonal and spatial merits.

I switched from the Decade Jubilee to the built-in phono preamp on my Wayne’s BA18 Line Stage. This is another DIY component, so while it’s not particularly useful to compare the sound or price of the two phono stages, it does illustrate the point I’m trying to make: listening to vinyl with my single-ended JFET phono preamp was dramatically more enjoyable than with the otherwise spectacular Lehmannaudio Decade Jubilee. On the one hand, the Armonía is picky, but on the other it rewards synergistic system-matching to a great extent. With this setup, songs like “Petal” and “Spike” came alive with good instrument separation, microdynamics, and articulation, while still maintaining the Armonía’s characteristic laid-back, slightly thick tonality. The dexterous, funky bass lines on Chon were well communicated, though perhaps they were not the strongest in terms of depth or punch. Rather, the Armonía sacrifices these traits for the sake, again, of tonal integrity and control. I count this as a strength; Ars-Sonum’s design has commendably avoided the loose, bloated bass that many tube amplifiers exhibit.

The character of the Armonía was such that I found myself compelled to do something that I otherwise never do: I turned the lights off and opened the windows during a listening session. This time, the album was Prologue by the Milk Carton Kids (256kbps AAC, Milk Carton Records / Spotify), and while it might be argued the Milk Carton Kids are just a touch too sophisticated to be considered campfire music, I certainly felt it was appropriate. In the dark, with the orange glow of the E34L filaments as the only light in the room, and a damp autumn breeze rustling the few remaining leaves on the trees outside, the wistful melancholy of the acoustic duo’s debut album just poured from the speakers. From the first notes of “Michigan,” what I found remarkable about the Armonía’s abilities was the sense of not just width and depth, but of height in the soundstage. Joey Ryan’s big-bodied Gibson dreadnought and lead guitarist Kenneth Pattengale’s Martin O-15 concert guitar appeared on the same plane, toward the left and right edges, respectively, of the soundstage. Their sonic images appeared at around waist height, and were credible in tone, depth, and size. The voices of the singers were clearly located higher, at head height, on either side of the center point between the speakers, and came through sounding natural and fleshy. Coupled with the overall richness I’d come to expect from the Spanish tube amp, I found the effect absolutely intoxicating; enough so that I kept returning to the album repeatedly throughout my time with the amp, turning the lights off and allowing the fall air into my home each time.

Sadly, replicating the Ars-Sonum amp’s homerun performance of Prologue wouldn’t prove to be possible on other music I played through the Armonía. As a half-joke, half-experiment, I tried out Led Zeppelin IV (LP, Atlantic SD 7208). The Armonía didn’t rock as hard as I would have liked, though listening was still enjoyable. In the absence of the red-blooded power and punch I’ve come to expect from Led Zeppelin played through solid-state gear, the Armonía meticulously presented the more subtle details and decisions made in the mixing and mastering stages. In other words, it gave a unique perspective on a work I am well acquainted with, and whenever that happens, I always feel a bit conflicted. On the one hand, the ability to re-examine something familiar from another angle always has value, and with audio as well as with life, this ability is a critical skill. On the other hand, when a piece of stereo gear shows a recording I know well in a dramatically different light, it’s obvious that this is only possible because the equipment is doing some sort of editorializing. How much this matters—and whether it’s better or worse for it—is subjective, a matter of the taste and personal values of the listener. But in any case, the effect was noticeable on the Armonía when playing material outside of the amp’s comfort zone. I will also note that the crossover design of my loudspeakers means they have an impedance spike around 1kHz, in addition to the more typical ones around the resonant frequency of the woofers. With other tube amplifiers with lowish damping factors I’ve heard, this speaker characteristic has given an added presence or brilliance that improved the clarity and detail of the midrange due to the altered frequency response. This was not my experience with the Armonía, on any material. Though no damping factor is specified, I suspect it is high enough that frequency response anomalies due to varying loads are not a problem, and the sonic characteristics I heard are due to some other parameter of the amp.

Para comparar

Comparisons with the Ars-Sonum Armonía are tough, because it’s hard to find components with world-class reputation and performance in this price range. As power amps go, the Luxman MQ-88uC, at $6295, is a worthy competitor if one is willing to dredge the bottom of one’s wallet in this price class. Many of the Armonía’s peers are integrated amplifiers, which include a preamplifier. Consumers have to consider the cost of pairing a preamp with the Armonía, and suddenly amps like the Decware Zen Mystery Amp (starting at $5995), the Cayin Soul 170i ($6499), the Leben CS-600X, and the Luxman LX-380 (both $7995) start to sound like outright bargains. The LX-380, for example, has a build quality at least equal to that of the Armonía. When I heard it, it impressed me more than the Ars-Sonum with its midrange purity and airy imaging precision, though the Armonía’s tonal density and upper frequencies just barely edged the Luxman’s. And the LX-380 comes with a quality onboard phono preamp, a volume knob, EQ controls, and a sharp-looking wooden case, to boot. No one ever said the decision would be easy!

Para concluir

When I finally came to writing up this review, it was time to circle back to a discussion around the task of matching speakers and electronics with the Ars-Sonum Armonía. The Armonía’s specs, as well as my experience, indicate that it should play well with most speakers one might pair with it. The electronics, on the other hand, can be more of a struggle, as witnessed by my phono preamp odyssey. The preamplifier, serving as the interface between the source components and the amp, is in my opinion the most crucial part. My BA18’s 12dB of gain was enough for the Armonía on its low-gain input, so I think that many tube preamps, like those in the tradition of the Marantz Model 7 or Audio Research SP-3A, might have too much gain to be compatible. Signature Sound’s Rich told me many of his customers like to pair the Armonía with tube preamps by the now-defunct Joule-Electra brand. All Joule-Electra preamps have a lower gain than my BA18, and some can be set to provide no gain at all, instead functioning simply as a buffer between the source and power amp. Unity-gain buffer preamps or even passive preamps should work swimmingly, though they aren’t really en vogue anymore. In a certain regard, pairing a passive pre featuring a good-quality stepped attenuator with the Armonía would be like getting a hot-rodded Filarmonía, as the only appreciable differences then would be in the quality of the volume controls and the output transformers.

So, as I often do when I’m evaluating a piece of equipment, I find myself asking: “Who is this for?” The Armonía is a true high-end tube power amplifier, with a sound, an aesthetic, and a design philosophy that caters to experienced tube-heads. I wouldn’t recommend the Ars-Sonum as a first tube amp for someone making the switch from solid state; nor is this the right product for an audiophile who isn’t willing to experiment and do the work to find the right equipment to match with it for optimal performance. But for the experienced tube-audio freak who isn’t afraid of spending the time and money to find matching equipment for ultimate performance, the unique appearance and sound of the Ars-Sonum Armonía is worthy of consideration.

 . . . Matt Bonaccio
mattb@soundstage.com

Note: for the full suite of measurements from the SoundStage! Audio-Electronics Lab, click here.

Associated Equipment

• Speakers: DIY Paul Carmody Amiga speakers, built from Parts Express kit.
• Subwoofers: Paradigm UltraCube 10 subwoofers (2) with MiniDSP 2x4 module for bass management; Jameco 170245 Linear Regulated DC supply for the DSP module.
• Preamplifier: DIY Wayne’s Burning Amp 2018 Line Stage; TentLabs relay-switched resistor-ladder attenuator; separate AMB Labs σ22 power supply.
• Power amplifier: McIntosh MA6850 integrated amp (using power amp input).
• Digital-to-analog converter: S.M.S.L D300.
• Television: LG C1 55″ OLED display, directly wired via Cat6e cable to router.
• Internet router: Netgear R6080, Jameco 170245 Linear Regulated DC supply.
• Digital link: Monster Cable optical cable.
• Turntable: Micro Seiki DQ-3 with Micro Seiki MA-707 tonearm.
• Phono cartridges: Audio-Technica AT95 with AT-VMN95SH Shibata stylus, Sumiko Blue Point No. 3 Low Output.
• Phono preamplifiers: Lehmannaudio Decade Jubilee, DIY Salas Simplistic N-JFET phono preamp.
• Analog interconnects: Shielded dual-conductor Canare and Belden cables with Neutrik and Switchcraft connectors, respectively.
• Speaker cables: Belden 9497.

Manufacturer comment:

On behalf of the folks at Ars-Sonum in Madrid, Spain, I would like to thank Matt Bonaccio and SoundStage! Hi-Fi for the thorough review of our Ars-Sonum Armonía power amplifier.

I think the review accurately reflects what Matt heard in his system; however, I would like to make a few observations that readers should keep in mind when reading the review and looking at the measurements.

1) Speakers and tube amps: With almost any tube amp, speaker selection is important in getting the best performance. While Matt touched on this, I would like to discuss this in greater detail.

It is not just the speaker’s efficiency and nominal impedance that are important for (mostly) tube amps, but also the nature of the impedance curve across the audioband. This is not discussed enough. Particularly important are large differences in impedance minimums and maximums (or to put it more clearly, the ratio of those minimums and maximums), especially in the mid band and low treble, where our hearing is the most sensitive. A large difference between minimum and maximum impedance can lead to a significant modification in the frequency response of the speaker/amplifier system. So, a 4-ohm speaker whose impedance varies from 3 to 8 ohms across the audio midband might well be a better match for a tube amp than a 8-ohm speaker whose impedance varies from 5 to 28 ohms across the same band. On the other hand, in some cases larger variations can help if, for example, the speaker has a dip in its (acoustic) response where the speaker impedance peaks. This can result in flatter response than you would get with such a speaker using a solid-state amp with low output impedance! I have seen such things happen. That’s part of the fun of our audiophile world, where there are so many speakers and amplifiers to choose from.

Based on measurements I have found (and those he mentions), Matt’s speakers have higher-than-usual variations in impedance in the midband. While Matt believes he was not experiencing any significant frequency-response modification (due to the Armonía’s somewhat lower damping factor compared to some other tube amps he may have used), I think there was a bit of that going on. I also think that was reflected in the issues Matt reported in matching front end ancillary gear to the amplifier. I believe that was further amplified by the Armonía’s transparency . . .

My only wish for Matt in his (bright) reviewing future is that he have more than just one pair of speakers (one with a more even impedance load and hopefully a bit more efficient than his Amigas) available to him so he can offer even better insights in his amplifier reviews.

2) Measurements: I have only one note to make here. The differences noted between the two channels in distortion measurements, output impedance, and some other measurements is due the right channel half (triode) of the E88CC tube not working “optimally.” I checked all the tubes in the amp using my Amplitrex tube tester before sending the Armonía off to SoundStage! Hi-Fi for review. All was good, but sometimes the tube gods (or maybe FedEx handling) get angry and bite you in the butt. In any case, the left-channel measurements (which Diego mostly used) are more representative of what the amp delivers from both channels. Ars-Sonum and I are very impressed with the quality and depth of Diego’s measurements.

3) Voltage gain: I’m glad Matt found the two different sensitivity inputs helpful in matching the amp to his system. If a customer needs even less gain from the amp, the Line 2 input can be configured with a bit more attenuation when we order a fresh amp from Ars-Sonum for a customer.

4) A point of disagreement I have with Matt is that I do not see that the Armonía as an amp for “experienced tube-heads.” Unlike many other tube amps, there are no biasing headaches to worry about with the Armonía. It’s very compact and very simple to operate—connect the speakers and source components, plug in the amp and power it on, then enjoy. It does not weigh 50 or 70 pounds, so it’s not hard to move around or place. The Armonía is very well engineered and built for many hours of trouble-free enjoyment.

Yes, some care needs to taken when choosing speakers to use with the amp—that’s true of almost all tube amps and other amps with similar or lower power outputs. That is where I (your friendly Ars-Sonum distributor) come in. I am more than happy to talk with anyone interested in a Ars-Sonum amplifier (new or used!) to answer any questions about compatibility with whatever gear and speakers the customer may have. As well, for those (tube-head) Ars-Sonum amplifier owners who wish to “roll” different EL34s (n.b., KT77s are not recommended), I am happy to test their set of EL34s in our Amplitrex tube tester and then try them in the Filarmonía or Armonía on my test bench to verify matching and that self-biasing measurements meet factory specs for the amp.

Best regards,
Rich Brkich
Owner, Signature Sound
Phone: 315-622-4137

Ars-Sonum Armonía Stereo Amplifier
Price: $5250.
Warranty: Two years, parts and labor; 30 days on tubes.

Ars-Sonum SL
Villagarcia 14 5B
28011 Madrid
Spain
Phone: (34) 91 711 31 74

Email: ars-sonum@ars-sonum.com
Website: www.ars-sonum.com

US distributor:
Signature Sound
8409B Shallowcreek Rd.
Liverpool, NY 13090
Phone: (315) 622-4137

Email: info1@sigsound.com
Website: www.sigsound.com