Moscode 401HR Tube Hybrid Stereo Amplifier

An audio classic, revised and updated.

One of the well-known downsides to planar or electrostatic speakers is that they aren’t simply hungry for current; they’re ravenous for it. Almost any speaker can benefit from gobs of power, but trying to satisfy the appetites of dipoles can be a particularly exasperating experience, one that has led some audiophiles to conclude that current-greedy speakers can’t produce realistic dynamic levels or are more trouble than they’re worth. High-powered amps that can provide slam and impact are, more often than not, extremely expensive and, in some cases, prone to producing an overly analytical or bleached-out sound, while less prohibitively costly ones may simply falter, like an underpowered car struggling up a steep hill, when pushed beyond their limits. So it was with more than a pinch of skepticism that I listened several months ago to designer George Kaye’s confident assurances that his new tubehybrid Moscode HR401 stereo amplifier would be able to drive Magnepan’s famously power-hungry flagship 20.1 loudspeaker with aplomb.

Would I really discover that his reasonably priced, by audiophile standards, amplifier, based, no less, on a classic design, differed from others that had made a good initial impression but ultimately failed to deliver the musical goods? Absolutely. Almost immediately after powering up the Moscode, I realized that it is not a good amplifier. It is a superb one. Sumptuous and dynamic, it conveys any type of music, ranging from orchestral to rap, with unusual authority and selfassurance. So fetching is the Moscode, visually and sonically, that I found myself eagerly lugging it to several friends’ systems, delighting in their stunned expressions as they discovered the smooth, grainless presentation of the Moscode as it powered their respective Thiel 1.6s and Kharma Midi-Exquisites. The $70,000+ Midi-Exquisites powered by a $5000 amplifier? You bet. The combo sounded ravishing. While the Moscode is not without some sonic flaws—find me an amp that isn’t, please—it can more than hold its own with any loudspeaker, regardless of cost. And there are few speakers, apart from high-sensitivity horns, that would not profit from the Moscode’s abundant reserves of power.

Right out of the box, there is no mystery about the sonic signature of the Moscode. If neutrality is what you’re looking for in an amp, then look elsewhere. The Moscode may have a solidstate power supply and output stage, but it errs emphatically on the side of a tubelike presentation. It is, you might say, about the lush life. In fact, after being on for a few hours, it becomes even more relaxed and tuneful than upon startup, erasing most traces of transistoritis, which can often be a welcome thing. Perhaps these qualities should come as no surprise given the intellectual provenance of the amplifier, which is a tribute piece to the late Dr. Harvey Rosenberg (hence the HR in the amplifier’s logo), a legendarily wacky and tube-obsessed designer of amplifiers (the owner’s manual comes complete with an introduction by Rosenberg for the original version of the amplifier in which he recommends, among other things, wearing a silk robe and indulging in a Shiatsu massage before listening to the amp).

Nevertheless, this is clearly no fusty museum piece from yesteryear, but a thoroughly modern design that never faltered or failed. Push the little button in front, watch the beautifully lit blue soft-start flash on and off as the tubes gently power up, and you’re off and running. So meticulous is Kaye that there is even a little dial in back to modulate the glow. A switch in back lets you use one amp in stereo or two in biamp mode. I ran the amps both ways, but preferred the added power of two. No matter where or when I ran the amps, they never failed to perform glitch-free. The only no-no that I indulged in was to flout the manual’s instructions and lift the ground on the amp with a cheater plug to banish a persistent hum.

One other thing: this amp is heaven for tube-rollers. For the gain tubes, Moscode gives you seven different options. Some manufacturers like to claim that they’ve voiced their equipment specifically to match certain tubes, but I’ve always regarded this as blarney. The advantage of using tubes is that you can tailor the sound to your preferences or change it if you want a change of pace. I didn’t do a huge amount of tube-rolling, but did learn that, in this case, the factory- supplied 6H30 sounded markedly superior to my vintage Telefunken 12AX7s. The sound became more refined, airier, and the bass tightened up with the 6H30s, but I also had to turn up the volume since the gain went down substantially. Others might prefer the more swollen sound of the 6DJ8 tube (which I really don’t think should be used in any audio applications even though it’s convenient and easy for manufacturers to source). Anyway, no matter what tubes you use, I’m quite sure that the basic sound of the amp will remain constant.