Grace Design m900 DAC/Amp

An updated version of the Massdrop x Grace Design m9XX combo unit, the m900 features the notable addition of an S/PDIF input. This makes it a great pairing for digital audio workstations, where you can plug in to enjoy reference-quality D/A conversion, headphone monitoring, and stereo speaker control. Plus, the m900 retains the same great sound of the m9XX. Both units were inspired by the world-class m920 DAC/amp and designed to offer the same performance level for audiophile applications, but at a far more accessible price. With the original m9XX, we worked with Michael and Eben from Grace Design to strip the m920 of its lesser-used pro audio hardware and improve upon the audiophile features where possible—all while retaining the high-res DAC implementation and super-clean solid-state amplification. To learn more, check out this review.

The m900 has a direct-coupled design with no capacitors in the signal path and the output amplifier is DC servo-controlled, ensuring zero phase shift for the ultimate in clarity and resolution. High-quality resistors in the circuit path help the m900 deliver a low-noise, low-distortion signal, along with dynamic accuracy and excellent channel matching to the headphones. The amplifier section is built around the TI THS6012 current feedback chipset, but has been modified with a proprietary circuit topology to zero output impedance for a maximized damping factor, even with sensitive IEMs. This allows the m900 to deliver all of the ultra-high resolution and clarity of a current feedback amp with all of the control and dynamics of a zero-output impedance headphone amplifier. The compact m900 even includes crossfeed circuitry that sonically distributes the stereo image across your headphones’ soundstage, helping to reduce listening fatigue over time. Toggle this on or off from the device menu.

The power supply design of the m900 is unique. In total, there are five separate power supplies at work delivering clean, isolated power to the digital and headphone amplification sections. The back panel features two micro-B USB connectors, one for connecting to a wall charger and the other for connecting to a USB source. The m900 can independently operate from its USB bus supply up to 100 mW of power into a 32-ohm load (per channel with two channels driven). Plug the device into the wall for additional amplification power up to 1,000 mW into 32 ohms (per channel with two channels driven). The power supply in this compact device is carefully filtered, with multi-tiered noise suppression for artifact-free playback from the sensitive DAC circuits and amplification unrestricted by any annoying buzz or background hiss. All that’s left is your music ripe with dynamic response, crystal-clear detail, and musicality unheard of in this price range.