NHT Pro M-00 Powered Monitors, April Music Stello DA100 DAC and HP100 Headphone Amplifier

Graduate from PC geekdom to professional audio in one quick leap

Previously distributed only through NHT’s Pro division, the M-00 and companion S-00 are now available to a much wider audience, according to a July 18 announcement. Even better, the price has dropped from an original $350/each to $250/each, according to the NHT Pro Web site. This translates to $500 for a stereo pair including high-quality amplification—and no need for speaker cables. For bigger, more immersive sound, add the S-00 subwoofer for an additional $500, and you’re in happy hi-fi land for a cool grand. There’s no better bargain in audio.

Imagine my surprise on the last day of the Consumer Electronics Show, when I walked into the April Music suite at the Alexis Park and had my socks knocked off by the very same NHT M-00s playing music off a notebook computer. I had the same setup at home, but the depth and dynamics in the April Music suite were immensely better. The difference was the Stello DA100, a USB digital-to-analog converter inserted between the computer and the speakers. It was a revelatory moment.

April Music chief and chief engineer Simon Lee asked if I’d be interested in taking the DA100 home for an extended test drive, along with its companion piece, the HP100 headphone amplifier/preamp, together marketed as the HiFi500. I jumped at the chance and haven’t regretted a moment since. Designed and built in Seoul, South Korea, entry-level Stello gear shares the audiophile credentials of the company’s more upscale products, such as the Stello DP200 DAC/preamp reviewed by Neil Gader in Issue 159.

The two units are built using the same half-width chassis, so that side-by-side they occupy the space of one traditional component. They can be stacked for desktop use. Interior construction is first-rate, with large toroidal transformers at the heart of oversized power supplies, and ultra-high parts-quality throughout.

The DA100 is a “true 24-bit delta-sigma” upsampling DAC with phase-locked loop (PLL) jitter reduction. It’s claimed capable of taking ordinary “Red Book” CD playback to the 192kHz/24-bit level of resolution of DVDAudio. Inputs include one coaxial, two optical, and one USB—an interesting array, given Simon Lee’s belief that “coax sounds better than optical.” A single pair of heavy-duty goldplated RCA jacks provides stereo analog output. A front-panel switch engages the upsampling function. A few moment’s experimentation convinced me that it adds tremendously to the sense of air, space, and dimensionality of digital recordings, compared to both the unit’s standard sampling and direct playback from my Marantz CC-65SE disc changer.

I found the $695 Stello DAC to be a substantial improvement over the Perpetual Technologies P-1A/P-3A combo (reclocking device and upsampling DAC, respectively) that has long resided in my system. Instruments and voices arise with startling clarity and apparent effortlessness from a dark velvety background. I also use the DA100 in USB mode to stream Sirius Satellite Radio via an older Sony Vaio notebook computer. The DA100’s performance in this mode is a night-and-day improvement over running the notebook’s headphone output directly into my preamp. April Music claims that the DA100 is capable of processing any digital audio stream up to 96kHz/24-bit, including the digital audio output from cable and satellite settop boxes.

Its most amazing and significant ability is lifting ordinary CD playback into the true highfidelity realm. Looping its analog output through a Margules Audio ADE-24 “Magenta” analog harmonic sweetener takes the whole affair up several more notches. The playback chain of Marantz CD player, Stello DAC, and Magenta analog processor yields CD sounds virtually indistinguishable from the same recordings in SACD format through a much more expensive Lexicon RT-20 universal-disc player. The April Music Stello DA100 proves that you can get world-class sound without throwing money into the wind. It’s highly recommended.

The $595 HP100 headphone amplifier features two pairs of stereo inputs, filter and gain switches, a Neutrik output jack that accommodates both XLR and ¼" phone plugs, an ALPS “Blue Velvet” volume pot, and a pair of analog outputs. The defeatable filter blocks frequencies above 20kHz.

I tried the HP100 with Sennheiser HD 580 headphones, JVC HA-D990 headphones, Etymotic Research ER-4 earphones, and assorted earbuds. The headphones themselves proved the limiting factor, not the headphone amp. Not in the Stax electrostatic realm of transparency, the HP100 is still a huge leap over the throwaway op-amps used to power headphone outputs on most consumer gear. As a preamp it’s very basic but more than adequate, and is perfectly suited as a controller for the NHT M-00 powered monitors. In fact, the April Music components and NHT speakers make an ideal compact, efficient, and greatsounding desktop or small-room audio system. Just add notebook computer and/or iPod, and you’re in the music business.

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