Note: I was using this product and was so excited about it, that I wrote this review. Then as I was finishing it up, I remembered Tom Fine already reviewed it a few issues back [Tape Op #124] – https://tapeop.com/reviews/gear/124/m900-headphone-ampdacpreamp/. I went back and re-read Tom’s review and in the end I think we both said different things about the m900 and even more interestingly, Tom’s one minor gripe about the m900 was implemented by Grace by the time I got my m900 a few months later. That’s a pretty responsive company!
About six years ago I bought a Grace m902 headphone amp/monitor controller/DAC [Tape Op #68]. It’s not something that I use every day in sessions, but when I do use it, it’s one of those tools that you’re thankful you have, and like all Grace products, you can’t help but be impressed with it’s sleek industrial design. At first glance, the 1/2 rack space m902 is a headphone amp but as you look closer it does quite a bit more. Sure it has two headphone jacks and a volume knob, but when you look around back you see how much functionality is packed into the m902. There are two analog inputs, balanced and unbalanced as well as a USB input. Besides the headphone outputs on the front panel, there are also two analog outputs. I recently put together a remote recording rig for artist Avery Hellman and engineer/producer Robert Cheek and we used the m902 as the centerpiece for monitoring the session. Our usage is a great example of the versatility of the m902. The stereo output of our RADAR rig running Pro Tools went to the balanced input of the m902. We had an 1/8” stereo jack going into the unbalanced input for Avery’s laptop and phone and a USB cable for Robert’s laptop. This made it easy to bounce between sources as they were listening to music in pre-production discussions. Robert brought a trusted pair of headphones for critical listening (we were in a barn) that plugged into the front of the m902 while one of the analog outputs fed a pair of Yamaha HS8 monitors and the other output fed a small pair of M-Audio computer/reference monitors. So with one small half-rack unit, we had a high end headphone amp and multiple source/destination monitor control. I’ve used the m902 on similar remote recording gigs over the years and it’s perfect for that, but would be equally at home in a small studio situation. And, in-between remote gigs the m902 went back home with me and acted as a DAC between my laptop and my Jolida tube amp. But since I’d moved a few years ago, I didn’t have as much space and the m902 was a bit awkwardly on its side edge as I didn’t have room for it to lie flat. So when I was chatting with Eben Grace at the recent AES show and he was showing me the new m900, which is much smaller than the m902, I was curious to check it out for my home set-up. The m900 is a bit simpler in terms of IO than the m902, but was all I needed for my home rig with a USB input – one unbalanced analog output and two headphone jacks on the front panel. There is also a S/PDIF and TOSLINK optical input. A big bonus in my book is that it is bus powered when using a USB input so you don’t need a power cable or wall wart which is nice. But there is a second USB input for power only so you can use an external wall wart supply if using the other inputs or an Android of iOS type mobile device that won’t supply power via USB. A volume knob sits on top of the elegantly spare, small three-inch square black box. It’s hard to really qualitatively AB test converters without a pretty involved set up that I don’t have in my living room. I will say that the m902 always sounded great to my ears, but I feel like the m900 sounds even better on playback of sources I know well. In particular the bottom end sounds tighter and more focused. The m900 is also 32 bit and supports sample rates up to 384kHz PCM or 256x DSD.
The other really cool thing about the m900 is that when you push the volume encoder in you can access some pretty extensive ‘bonus’ features. Crossfeed can be turned on or off for the headphone outputs and you can switch between four different DAC filter settings for instance. But, what I think will be of the most interest to a lot of Tape Op readers is the ability to switch monitoring modes, similar to the Little Labs Monotor [Tape Op #117] for instance. There are seven different monitoring modes available: Mono, left minus right, left and right swapped, left on both channels, right on both channels, left only, right only and of course normal monitoring mode. I have a Monotor at Panoramic and it’s amazing for checking mixes on, so having these functions on the m900 is really useful. I would highly recommend either of these units. The m902 is no longer in production but can be found on the used market. The m900 is in production, and while it’s a bit more money than the Dragonfly type USB DACs, it’s a substantial upgrade in terms of functionality while still being portable and bus powered.