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…and Twins?: When One Output Device Is Better than Two

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Art Audio PX-25 amplifier
Wavelength Audio Cardinal X2 amplifier
Art Audio Jota amplifier

Guys often dream about twins. But are two really better than one? If an arrangement with one takes daily work to make things run correctly, imagine trying to coordinate two in just about any situation. Ain’t gonna work–or at least not smoothly. Twins. Nice idea, but not ideal.

In audio we have a similar quandary when we get into the area of amplification. A single-output device–the electrical component in the amp that actually powers the speakers–can do a damn good job of creating music but is just not as potent as two devices working in tandem. And we really want more power for our speakers, don’t we?

Well, actually, music, as with most things, is not all about power. What we really want is quality, and more power does not necessarily mean more quality. Familiar story.

The fact is most amplifiers are designed around twins–twin-output devices–even in solid-state designs. In so-called push-pull designs, two-output devices attempt to perform the job of one device by dividing the audio wave–a more-or-less even sine wave that modulates up and down across an imaginary base line, into two pieces: the part above the line and the part below the line. To re-create the wave perfectly, these output devices have to be perfectly identical twins. And in the physical world, that just ain’t gonna happen. Solid-state devices might get close, but trying to get two vacuum tubes, organic devices with a known self-destruction cycle, to perform identically over time is impossible. Push-pull tube amps can sound great and, because of the nature of tubes, far more musical than solid-state amps, which typically are push-pull designs themselves. But they still leave something behind, and it’s something you just might not know is missing until you go back to the basics.

And in audio-amp circuits, the basics usually imply what is called a single-ended design. In this type of amp, most commonly found utilizing often exotic power tubes called triodes (thus, single-ended triodes, aka SETs), the final powering of the speakers is handled by one, and only one, output device: the power triode. By keeping that sine wave a unified whole, there is no chance of suffering mismatched tops and bottoms of the sound wave, and so the sound remains pure and faithful to the original.

“One tube will always do better work than two,” says Gordon Rankin, founder, designer and chief engineer at Wavelength Audio, one of the leaders of the single-ended amp category, “the least amount of ‘moving parts’ is going to give the best results in audio. Push-pull has so many things going against it. Trying to get those two tubes working together just never works. Anything that happens in one tube that doesn’t happen in the other affects the sound. One tube, no matter how well it’s matched to the other, will always, always, sound different from the other tube, even after just a few hours of operation.”

Rankin has done his share of spreading this gospel to musicians who, he says, routinely make the same comment: “That’s unbelievable.”

It’s that naturalness of the sound referred to earlier that is one of the chief characteristics of the single-ended amplifier.

“Even a mediocre single-ended amp does one thing well, and that is naturalness,” insists Joe Fratus, the high-energy force behind Art Audio (, another primary mover and shaker in the single-ended world. “It’s the closest thing you’ll get to live music,” Fratus says, “Instruments sound like they do in real life. You can pick out all the nuances in recordings, like the differences between horns, even horns in the same family, or pick out the distinctive voices in a vocal recording.

“The single-ended magic comes in part from the detail and resolution,” Fratus, a former jazz bassist, continues. “With a good SET, you are brought into the performance hall or club; you can actually feel the space. But it is also about dynamics. You get a coherency from the top to bottom I don’t hear from push-pull or transistors. It’s just like in a concert hall; the sound is lifelike whether it’s a soft, delicate triangle or a booming tympani. It’s just magic. And you don’t need to get the volume way up to get that magic.”

Fratus agrees with Rankin that more parts just get in the way. “At Art Audio, our philosophy is to keep things simple. We try to build amps that sound natural; we don’t go out looking for bigger bass or louder volume. We use simple circuits derived from designs; of the late 1920s, but we are better at maxing out the tube’s performance in our designs; we know better how to build the transformers and power supplies for the amp to get the best performance and reliability.

“But adding things to the amp to get more volume is not an option for us,” Fratus says. “Adding more tubes, for example, makes the sound worse; you add noise, change the sound and add distortion that will take away that naturalness we are striving for. Less really is more in this case.”

Fratus has also spent time converting musicians into the SET fold. He recently spent some time with Arturo Sandoval in an interesting demonstration. Sandoval was recorded with several other players, and the resulting session was played back through a pair of Art Audio amps and a pair of Bosendorfer loudspeakers. Fratus relates the story: “We said, ‘Sit down and listen for yourself.’ He was late for a gig at the Blue Note, but he didn’t want to leave the demo. After just a few minutes he started talking about getting an Art Audio system for his home. Man, I think we blew him away!

“But it’s always that way,” Fratus goes on. “It’s difficult to convince someone of the difference an SET can make unless they hear it for themselves. But every single time, the musicians we do this for agree that the sound is the best they’ve ever heard, even when we play them their own recordings.”

Gordon Rankin–who built his first single-ended amp in 1988 and has now constructed more than 750 SETs and more than 1,100 tube amps in all–explains a bit more about the sheer musicality of the SET: “When I built my first 45 [a type of triode-tube] amp, the sound was more like music than anything I’d ever heard before. It was a stellar moment. As a musician myself, I have to say that music played through a single-ended amp just sounds more like real instruments. And through a push-pull amp, it always sounds like music played through an amplifier.”

Rankin, a drummer who also plays other instruments, from woodwinds and brass to a wailing electric guitar (his single-ended guitar amps are becoming a cult favorite in the studio), elaborates on how the SET experience can provide musicians, or just civilian music lovers, with a more rewarding, more complete listening gestalt: “When I talk to drummers, I explain that cymbals don’t sound flat as they do through traditional amps; instead they have more harmonics, they have a richer sound. For guitar, you hear more of the natural sound of the instrument, more details and even more fret noise. With singers, you can often hear when the singer weaves a bit in front of the microphone. You just hear more of everything.”

I have to agree with Rankin and Fratus. I have long been a tube devotee but drifted away for a time. But at the 2005 Consumer Electronics Show, I experienced an epiphany that brought me back into the congregation of SET devotees. The importer of an expensive German push-pull amp was giving me a demonstration of his amplifier. The sound was nice, but nothing spectacular. When he was finished, in a different part of the same room, another manufacturer cranked up the same model speaker but used an SET to power them. After hearing only a few seconds of music through the SET-based system, my ears perked up, and I knew something special was happening. I was engaged with the music in a way I had not been through nearly four days of auditioning audio gear. I was rehooked, and now I am a happy SET owner once again.

The only downside to SETs is their relatively low power. Ranging from as low as a half-watt to 20 or so with certain modern triodes, these amps require careful speaker matching. It is important to pair them with speakers of greater than average efficiency, perhaps nothing lower than 90dB efficient, depending on the amp and on the speaker’s other characteristics. For example, the DeVore Fidelity Gibbon Super 8s, which I discussed in the last column, rated at 90dB efficiency and were capable of creating some quite nice music with only three watts of SET power. But this is a tricky matter, and you need to carefully discuss your particular needs with a qualified dealer to avoid underpowering your speakers or to avoid buying speakers that will not mate well with your SET.

But when it all clicks, it’s musical nirvana!

A couple of other affordable speakers that mate well with SETs have appeared on the market in recent years. To audition each of these, I used the quite exotic Fi “X” amplifier ($895) built by Don Garber. It is based on the classic 2A3 triode and creates some absolutely stunning music when powering the right speakers.

The Horn Shoppe Horn ($775/pair; is a compact design created by the somewhat eccentric but absolutely delightful Ed Schilling, an SET devotee from way back. He designed the speaker to mate with the Fi amp and it does so beautifully. It is a single-driver speaker, meaning it utilizes only one actual speaker to cover the entire frequency range; it utilizes crafty cabinet design to reinforce the low end, which the four-inch driver would otherwise be unable to reproduce. The sound is amazing and at about 100dB efficiency can rattle the windows and make the dog howl with just three watts. There is surprising bass, and when properly positioned they create a broad soundstage–a true wall of sound.

With music, well, just sit back and listen. With female vocals, the sound is lifelike and convincing. Remember the word natural? Well, it’s here in spades. On Eric Dolphy’s “God Bless the Child” from his Illinois Concert CD, the bass clarinet is right in the room. You can hear the air coming through the horn, and there is an outright rightness of the timbre, of the expressiveness, of the musicality.

Omega Loudspeakers ( are the product of Louis Chochos, another music lover turned designer. His new Omega HempTone Compact 8 ($1,299) is also a single driver system that is scary good. Its cone is crafted from hemp and has a prodigious amount of bass, way more than it should, and it’s quality bass, never boomy. But again the main characteristic is naturalness. On a Buddy Guy and Junior Wells disc, Alone and Acoustic, the vocals are palpably real and Guy’s guitar is presented in lifelike Technicolor; it’s just like the real thing, a steel-string, big-body acoustic. Another blues great, Son House, was in the house with his spine-tingling, chilling voice. The Omega/Fi combo created a believable image of House in my living room. These HempTones really smoke.

Rankin’s most successful amp is probably the Cardinal, now the Cardinal X2 ($7,500/pair), a design based on the most popular power triode for audio, the Western Electric 300B. The Cardinal monoblock amps are a study in simplicity, employing just three tubes and a handful of parts under the chassis. But that less-is-more thing is hard at work with these masterpieces of audio design.

I have only heard a couple of amplifiers that sound as good as the Cardinals, and at least one of those comes from Fratus’ Art Audio. Rated at only about 12.5 watts, nonetheless the Cardinals create an illusion of live music that is difficult to match with a naturalness achieved by few others. The music just flows out of the speakers, in this case the DeVore Super 8s. Regardless of style–from loud, raucous Jimi Hendrix to tender vocal renderings by Holly Cole–the Cardinals do it right, do it effortlessly and do it engagingly. Once powered up, it is difficult to stop listening to the simply gorgeous music these twins reproduce.

One night I had friends over for some system demos, and the overwhelming opinion was that the refinement of the Cardinals was far more enjoyable than the somewhat clunkier but much more powerful presentation of another pair of amps. “Put the Cardinals back in the system” was something I heard more than once that night. If you truly love good music and strive for excellence in performance, then consider making a nest for these Cardinals in your living room.

I’ve had the good fortune of auditioning an Art Audio Jota ($8,800) in my home on two occasions, and I always hate having to return the review sample. This will be no exception. The Jota was my introduction to the spellbinding qualities of the SET and holds a special place in my audio heart. It uses the 300BXLS tube, a variant of the classic 300B, which allows the Jota to offer a bit more power: in this case about 20 watts per channel–20 beefy watts at that–so the Jota is compatible with a wider range of speakers than many lower-powered SET amps. I’ve had no problem driving any of the speakers that have come through my living room, and that’s been a very diverse array indeed. And each and every time, the Jota produced a level of quality and naturalness Fratus claims to be after and has very certainly achieved. It’s the kind of sound that raises goose bumps, that startles, that just plain captivates and satisfies.

The robustness of the construction, the handsome design and the stunning sound make the Jota a worthwhile investment in first-level audio performance that will soothe the savage beast for years to come. I’ve found new life in my LP and CD collections while auditioning the Jota, discovering details I’ve never heard in discs I’ve listened to hundreds of times. But it goes beyond those details, those little tidbits. It’s the macro view, the impression of correctness, of real music–just as Fratus insists.

Originally Published