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Positive Feedback ISSUE 15
september/october 2004


My Audio: Introducing SinglePower Audio Supra headphone amplifier
by Gary Beard


Every now and then, an audio experience can be exhilarating. A few months ago, I put the wraps on a side trip into the land of high-end headphone gear, during which I had the pleasure of hearing one of the finest-sounding amplifiers I have ever heard. I had intended to break this news in a review, but due to factors beyond my control, the review never materialized. However, a promise is a promise, and I have now gone through that almost-completed review in order to present a short but sweet introduction to a relative newcomer in the world of high-end audio—SinglePower Audio.

The SinglePower Supra headphone amplifier that I heard was one of the first of a batch of handmade wonders. It has since been replaced by a newer, more commercially appealing model that uses the same technology. Designed and built by Denver resident Mikhail Rotenberg, my Supra was a no-frills, single-ended, output-transformerless amp built around the beautiful tone of the 6SN7 dual triode vacuum tube. SinglePower Audio builds several tube-based headphone amps, but the Supra was—and I believe still is—the unadorned version of their top-of-the-line headphone amp. In classic tube amp tradition, the Supra is totally point-to-point wired. My version was all business, with one pair of RCA inputs on the right side of the chassis, a single headphone jack on the left side, an Alps volume control in front, and a power switch and fused IEC power connector on the back. Three Electro-Harmonix 6SN7 tubes were furnished with the amp. My Supra had the sole option of upgraded RCA input jacks, which I ordered to allow the large locking connectors of my Acoustic Zen interconnects to have something substantial to grab. Cosmetically, this Supra was a throwback to another age. Its handmade, all-stainless-steel chassis looked as if it belonged on the con of Flash Gordon's spaceship, or perhaps like some kind of funky 1950s kitchen appliance. It was also a rather large piece of kit, and it was a challenge to find a place for it on a crowded audio rack. It had a decidedly Spartan look, and rang just a little if you “pinged” it with your finger, but this first incarnation of the Supra was made with care, and whether you loved it or hated it, it was the product of an unmistakable audio vision.

The Supra circuit utilizes three 6SN7 triodes, one for driver duties and the other two for left- and right-channel outputs. A model of simplicity, it has no feedback, a short signal path, and a bulletproof power supply. Mikhail Rotenberg believes that the power supply is the key to a great sounding amplifier. The Supra's overbuilt regulated power supply features two humongous Mallory power capacitors as big and blue as Labatt's cans, and a brutish Hammond power transformer ensures that voltage sags cannot affect the performance of the amplifier. This massive power supply creates a lot of heat, so a small fan inside the chassis keeps the amp running cool. I don't like fans in audio equipment, but it was necessary in this case. (The new outsourced chassis design is quite beautiful, and is more structurally sound. Rotenberg has also redesigned the cooling system, so my comments about the fan are moot.)

The original Supra sounded very impressive. Although it had the power to drive my old Sennheiser HD600s to places they'd never been before, one of its greatest strengths was how wonderful it sounded at low volume levels. It had a deliciously beautiful tone. Voices and instruments had a certain rightness of sound that was simply fabulous. I was also taken by the amount of detail I could hear. Although the Sennheisers do not have the detail retrieval of some headphones, with the Supra I could hear every squeak, every breath, and the pluck of every string. While not to be compared with the copious volume and visceral feel of good loudspeakers, the bass produced by the Sennheisers with this amp was amazing, although to get the full effect I needed to turn up the volume to at least 10 o'clock. The Supra was able to reproduce beautiful textures and luscious tonal color, and it conveyed musical emotion in a way that grabbed me by the ears and wouldn't let go.

Some say that the Sennheiser HD600s sound veiled and boring, but they did not sound veiled or boring when driven by the Supra. With good 6SN7s, there was a breathtaking purity of tone. While there was warmth and liquidity galore, there was also attack, decay, texture, bite, and edge. Every pluck of a string, blat of a horn, or warble of a voice was followed by enough resonance, harmonic overtones, and truthful timbre to entice the most seasoned listener. What comes out of the Supra depends greatly on the quality of the recording and the character of the tubes. The sound can be anywhere on the scale, from as rich and warm as brownies fresh from the oven to just slightly on the warm side of natural. Most audiophiles agree that everything we do to as audio system affects what we hear, so while the recording and the tubes make a tremendous difference, so do a myriad of other things—sources, cables, and in this case, headphones. I suspect that each pair of headphones generally regarded in the top tier will have its own voice with the Supra. I believe that Mikhail Rotenberg voiced the Supra with the Sony CD3000s, and Supra owners have reported excellent results with many headphones, including the vaunted Sony R10s. I found it very difficult to fault the Sennheisers when used with the Supra. I had hoped to find out how well other fine headphones fared, but alas, poor Gary had too much ear trouble and had to sell the headphone farm.

Despite my ear problems, my love affair with the Supra was enthralling. Listening to music gave me great joy, and the Supra allowed me to delve more deeply into good recordings than ever before. Other than the deep and visceral bass of a speaker system, I found nothing missing from the sonic picture. As much as I love a great soundstage and realistic imaging, the lack of these attributes didn't bother me. I believe that most people, even diehard speaker hounds, would enjoy what the Supra has to offer, but for those who love great music and who can't for some reason own a speaker system, the aural landscape has a terrific new entrant. My "classic" Supra would still be on my audio rack if not for the demons of audio-related ear pain. Whoever owns her now (you know who you are), you'd better feed her some great tubes and great music, because she deserves them. I feel very fortunate to have spent some time with the Supra.

If you are in the market for both uniqueness and awesome sound, the early version of the Supra is still available by special order, though I suspect that most buyers will prefer the looks of the new chassis and the other improvements made to the current version. Headphone audiophiles who crave the fabulous sound of single-ended triodes will certainly want to hear the newest Supra. That said, Mikhail Rotenberg's first Supra is a true classic in my audio book. Gary Beard

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