Like an EL34, the 6SN7 has tone. I'm sure that's why Mikhail is stuck on this tube and declared it his favorite for headphone applications. Having worked in Mesa Boogie's HiFi division, I know a little bit about the concerns for tone that go with the territory of musicians who plug their guitars into not just amplification but sound-shaping devices. Any discussion about tone invariably connects with their world which, apparently by definition, revolves around a different moon than High-End audio. Their kind of tone is additive and the result of tailored distortion. Our kind of the tone is the truth on the recording and nothing but the truth. Right. The fact remains that the timbre of a real instrument is nearly more complex and sophisticated than what remains after it's been siphoned through the recording and playback chain.

As Anthony Cordesman stated very succinctly in his recent TAS review of the Talon Firebird, live music from just a few meters away has more warmth and less transient sharpness or so-called hyper detail than much of what goes for superior HiFi. If you side with Mr. Cordesman's observations and conclusions, the SinglePower MPX3 will be far more rather than less truthful to your ears. Sure, truth remains a somewhat abstract concept. But sheer listening pleasure and absence of irritation or subliminal recoil is a very practical and experiential matter that involves your whole being and not just the argumentative mind. While calling the MPX3 truthful per se is fraught with potential disagreements, calling it eminently listenable and in the service of long-term comfort, involvement and enjoyment is a simple empirical matter. How long of a listening session can you have with it? Do you feel exhausted or invigorated afterwards? Do you suffer inner-ear ringing? Do you find yourself turning the volume up or down?

That last question in particular is quite vital. Components that lack tonal fullness demand to be goosed. In an effort to get the 'more' you sense they're withholding, you end up with more of everything. Naturally, that only further compounds the absence - but in louder and more irritating terms. Sheer volume simply is fullness of a different sort that's often invoked to make up for something else. Alas, those are calories of an emptier sort. When I'm calling the MPX3 possessed of tone, I'm referring to the kind of fullness that's not a function of loudness at all but one of harmonic density, dynamic responsiveness and spatial presence. This fullness arises very early on in the volume games. A good way to imagine how it works is minimal photographic under-exposure. Colors get richer, shadows deeper, tonal values saturate. Where this analogy fails is in the implicit suggestion of darkness. The MPX3 doesn't sound dark at all. It's warm but not dark. That's because it's not suffering treble roll-off; because its dynamic fortitude doesn't signal slowness; and because the THD content isn't out of control but in control and calibrated perfectly.

Thus far my listening had taken place using my favored audio-technica ATH-W1000 'phones and a set of tubes designated 'for serious reviewing' - one Kenrad 6SN7 followed by two Sylvania VT-231s. However, Mikhail had also included a triplet of Electro-Harmonix valves, a Tung-Sol driver and Sylvania and Kenrad 6SN7GT output valves while my Sennheiser HD650s were still waiting at the sidelines. Time to roll some tubes and cans...

While I still had the reference set of tubes in place, I switched to the Sennheisers using "Inolvidable" from Lagrimas Negras. Boy was I in for a surprise. Reader who've followed my recent headphone-related exploits will know that thus far, I hadn't really cottoned to the HD650s in any fashion remotely reminiscent of the major acclaim they enjoy elsewhere. I felt that compared to the W1000s, they lacked in dynamics, bass wallop and LF extension. Driven by the MPX3, they now had the warmth they lacked before but more surprising, bass that was tauter, "springier" and more pronounced than over the Japanese cans. This leads me to conclude that the power supply in the SinglePower unit is indeed endowed with particular testicular fortitude or, in audio slang, major stiffness.

I always knew that the audio-technicas were the easier load and one apparently optimized for applications not requiring dedicated amplification. Instead, they're perfectly happy to slurp juice from a standard headphone jack. Over the previously reviewed and transistorized Aural Audition amplifier, the Sennheiser had shaped up to reveal what all the fuss about 'em was - well, about. No matter, with that amp, I'd still preferred the W1000s for their greater musicality. With the MPX3, however, the Germans had now secured a small aural lead while their vise-like grip of the spring-loaded band still made wearing comfort a distant second to the Japanese luxury spa treatment. But the point is this - for about half the price of the Aural Audition and with the HD650s, the MPX3 delivers performance that's more copasetic with what -- in my book -- these famous cans require to really perk up and let 'er rip. Consider me a late-blooming convert of sorts then to the Sennheiser party everyone else is already attending.

If Mikhail's published insistence on the importance of power supplies was clearly no mere braggadocio, then his preference for the tube set specially marked for serious reviewing gave further credence to his 'no bull' MO. The triplet of Russian Electro-Harmonix, while perfectly acceptable, was coarser and did not have the sheer finesse of the Kenrad driver/VT-231 buffer set that tied together raw data facts of fine details with the emotional implications of the artistic message. There's no reason to belabor this point considering how affordable a starter set the Russians make. But serious listeners are advised to explore the upgraded valve options SinglePower recommends and has available. The surcharge is well worth it. I also sampled the Tungsol driver/6SN7W trio and the Kenrad buffers and can see how different listeners might favor specific combinations. My favorite set happened to be the one Mikhail seems to have predicted. This simply added to the overall impression that his MPX3 is exactly my kind of audio device and its designer someone who shares my particular preferences and biases.

Just because I favor tubes in general doesn't mean I automatically like a component that employs them. Far from it. Although it seems easier to design musically satisfying tube equipment than solid-state, proponents of the latter simply have to work a bit harder to achieve the same satisfaction while then playing their trump cards of lower or no maintenance, lower noise and universal speaker drive. To get tube gear to compete with the resolution, linearity and control of transistorized components is where thermionic designers have to work harder. The challenging aspect there is to not relinquish certain tube attributes while questing to capture solid-state strengths - something I sense the more expensive Emmeline II Stealth is just a little bit guilty of.

Wrapping up and being the agonizing audiophile, I naturally have to wonder just how much better the subsequent models in the SinglePower catalogue might be. While I can't be sure, I have a notion. Headphones aren't the kind of monster loads certain speakers represent. There's no crossover, no multiple drivers, no large excursions nor the fierce back EMF created by them. Upping the ante in the power supply beyond what's already in the MPX3 should thus net less massive returns over headphones than you'd expect with speakers, especially the dastardly low-impedance kinds beset with gnarly phase angles. Reducing global gain in the dearer units will drive down the noise floor yet lower to enhance micro-level resolution - though it's hard to imagine why you'd feel the need for even more resolution. There's probably a very good reason why the MPX3 is the best-selling model in the line. It must sit smack at the point where the law of diminishing returns causes the steep more-for-more angle to peter off and become a much-more-for-less-and-less slope of shallowness.

Let me put it to you this way: From what I've heard thus far and considering the cans I own, the SinglePower MPX3 with today's internal and tube upgrades is unequivocally my favorite headphone amp yet. It's the one I'd buy even if I had $2,500 to go on a rampage with - er, splurge on. Like the Wyetech Labs Pearl preamplifier, this is a tubed component that has the resolving power and mandatory low noise floor to show you what's on your recordings while adding that certain controlled magic only valves in the hands of a true master designer can give. The continuously adjustable gain control makes it easy to find just the right level and its taper avoids coming on too quickly to be useful even with high-efficiency 'phones. Fit'n'finish is beyond reproach though clean freaks will sweat over just how to keep finger prints and dust off its high-gloss coat. has clearly done a wonderful job to promote this company and its products to the in-crowd of headphone aficionados. It's my hope that our review will continue that process into the ranks of our readership and that other publications will pick up the ball and run with it even farther. Plainly put, this is a company to watch, and the MPX3 a component that's a no-brainer to recommend and, considering what it competes against, a very fair value. Now imagine two dumbo-sized ears wiggling in ecstasy in the direction of Monsignor Rotenberg and his team. Time to smack our award seal onto this virtual page!
SinglePower responds:

Hi Srajan,
Thank you for a thorough and very well-written review. We’re very gratified that you chose to honor the MPX3 with the Blue Moon Award. Your review is very similar to what our customers have been saying. The review describes very clearly what we’ve been trying to accomplish with our amplifiers. We’re happy that you enjoyed listening to the MPX3, and hope that you will have a chance to review some of our other products in the future.


Mikhail Rotenberg
Singlepower Audio Inc.

Manufacturer's website