I wanted to pass at least a reasonably brief review of the DAC I got recently from Ross Martin Audio, the PCM1794 Dual “Bare Beast”, which has two optical inputs, two SPDIF inputs, does 96Khz via USB and a headphone amp. It also has balanced XLR as well as RCA outputs. Ross is also very amenable to customization, and I had him use OPA627's (which I provided for him to keep the cost down) and OPA1602's as the opamps. I haven't come across much on the 1602's before, but the specs looked good, so I went with it. The cost came in around $350.
There's a really nice and comprehensive review on Head Fi, so I'll provide the link. http://www.head-fi.org/t/573586/review-ross-martin-pcm-1794-dac-250-overachiever
The reviewer had the single input version of the DAC and had gone with LME 47910 and LME47920 opamps, so there may be some differences between his version and my own, but I can't imagine that the differences are huge. I also don't have filters to choose from.
Anyway, I first used the DAC in both my computer system where I had been using a Maverick Audio Tube Magic D1. The D1 is not stock, but it the mods are all reversible. I'm using a Raytheon JAN-5670 tube, OPA627 opamps, and replaced the stock fuse w/ one from Radio Shack (a trick I find usually helps w/ the sound). It's a DAC with a pleasant, non-fatiguing sound. Not the last word in anything, but solid and enjoyable across the board. I also use a glass toslink from Fleebay, which I find sounds much better than the USB. The amp is a modded TCA Gizmo and the speakers are the very solid Dali Mentor Menuets. Anyway, as soon as I put the Ross Martin in the system there was a noticeable difference, which I was not expecting. I've usually been of the opinion based off of my prior experience as well as a DAC shootout I participated in, that while there are differences between DACs, they are subtle and difficult to describe. Here the Ross Martin had clearly better detail, separation, and a sense of dimensionality to the images. Now, you can say that the differences are due to the tube in the D1, but I personally haven't found that the tube makes that much of a difference when I switch the D1 from tube to "normal" outputs on the D1. The difference to me is in the musicality and the ease of listening of the music. Interestingly, the Ross Martin retained this musicality as well. Instruments sounded like instruments, the same way I was used to.
A couple of other things about this set up. First, I didn't notice that much of a difference when I switched to a USB input. I found I preferred the toslink input, but that's probably because I don't have any high quality USB cables laying around. Second, even though I found the Ross Martin to be better than the D1, I didn't keep the Ross Martin in this system. The Ross Martin is a bit more forward than the D1, and I also found that it I was more drawn into the music w/ the Ross Martin, which made it more difficult to get any work done. So, this isn't a "problem" per se, and not a knock on the Ross Martin.
I next put the Ross Martin into my listening room system. This system is pretty highly modded, including a Sony DVD player (can't remember the model), a MHDT Labs Constantine+ DAC, a 200 watt per channel AudioSource T amp, and Onix Strata Mini's (with Ninja-modded crossovers w/ Sonicap Platinum bypasses). Here, the differences were not as great, but similar to what I'd noted before and also noticeable even on a quick listen. Now, the sounds flew off the speakers, the sounds were more clearly separated and distinguishable, the detail went up a few notches, and the tracks were even more musical. And since this is a system that's specifically for listening (and perhaps some light reading while I'm listening), this was a very good place for the Ross Martin's presentation.
A few other thoughts before I wrap up. First, I can't honestly compare the Ross Martin to any other DACs since I haven't tried others in my systems. So, I'll defer to the Head Fi reviewer on this account. Second, Ross was very responsive to my questions when I emailed him. It did take him a bit longer than I'd have liked to get it to me, but given my ability to customize the DAC, it was worth while.
So, overall, the Dual Bare Beast is a very nice DAC, and I've been pleasantly surprised by the improvements I've heard with it in my systems. I'd have to imagine that it could compete if not better many of the DACs in the sub-$1000 range.