This is a review and detailed measurements and comparison of Massdrop Grace Design SDAC DAC. It is on kind loan from a forum member. The "drop" is over but when it was active, the unit costs $79. See it, and the detailed specs here: https://www.massdrop.com/buy/massdrop-x-grace-design-standard-dac The unit is similar size to JDS Labs OL DAC ($99 plus shipping) which I compared it to in this review:Clearly they are after the same market and audience. While both have decent heft for what they are, they are both too light so support heavy cables and such.The JDS OL DAC comes with an external linear power supply while the Grace SDAC is USB powered. The designer, Michael Grace, has written a nice post about the SDAC here: https://www.massdrop.com/buy/massdrop-x-grace-design-standard-dac/talk/1806625 . Reading that, seems like good engineering has gone into the device beyond just slapping a reference design in a box. Measurements of course will tell if that is, or is not the case.The unit is UAC 2 compliant meaning it worked without installing and drivers in Windows 10 Creators edition. I tested it as I do all other USB DACs using Roon in "exclusive" WASAPI interface which gives bit-exact access to the DAC.I am sure you are anxious to see the measurements so let's get into that. If you are not familiar with my measurements, I suggest reading my tutorial on audio measurements here: https://www.audiosciencereview.com/forum/index.php?threads/understanding-audio-measurements.2351/ And oh, unless I specifically say otherwise, I have no relationship to these or any other manufacturers.Let's start simple and look at frequency response measurements using 48 kHz sampling:I was surprised to see that early roll off in OL DAC's response starting at just 10 kHz. The graph has very fine scale so that is not a large drop but still, at 48 kHz sampling, I expect to see pretty flat response to 20 kHz which the Grace SDAC delivers. Importantly the SDAC has higher output which may be necessary to drive some power amplifiers to their maximum output. The SDAC output is 2.16 volts RMS whereas the OL DAC was 2.00 volts (@ 1 kHz).Channel matching while not an issue, was slightly worse on SDAC than OL DAC as you can (barely) see in the graphs.Next let's look at jitter and noise with a 24-bit, 48 kHz signal. Everything other than the main tone at 12 kHz is undesirable:The Grace SDAC nails this test with a flat, low noise floor free of any distortion or noise spikes. The OL DAC does nearly as well but its noise floor is a few dB higher and we see widening of the 12 kHz "skirts" which indicates some amount of random jitter. Mind you, these are all, literally in the noise and the OL DAC response is very good. Still, in a race to best engineering, the SDAC wins here by a bit.Linearity test is the favorite for everyone so let's see how they both did:Both provide good performance but the SDAC again pulls ahead by a bit. The same is reflected in time domain response of a low level, -90 dB sine wave:Next let's feed them a 1 kHz tone, filter that out from their output and see what remains:While the SDAC shows lower noise, in a reversal of fortunes, it has higher harmonic distortion than the OL DAC. Some or all of this may be due to higher output it provides. I had no good way of taking that effect out of that this test.Let's look at how the harmonic distortion and noise act versus level:The OL DAC shows a lower (but insignificant) amount of THD+N than SDAC. Both display a bit more distortion close to their maximum output level. Note that these are at 400 Hz rather than the more common 1 kHz (limitation of the test file I am using at the moment).We have a bit of mixed picture in the measurements here relative to the two DACs under test. Overall though, I would give the nod and recommendation to Grace SDAC for exemplary jitter response, lower noise floor, higher output and flat frequency response. Its harmonic distortion is higher than I like but in this price bracket and audibly, not a concern.It is clear there is good engineering behind Grace SDAC. It is also a good value at just $79 from Massdrop. Alas, you can't buy the unit right now so take that into account when deciding what to purchase.Edit: fixed the comment about output levels and updated the measurement/graphs for THD+N.As always, questions, comments, corrections, etc. are all welcome.----If you like this review, please consider donating funds for these types of hardware purchase using Patreon ( https://www.patreon.com/audiosciencereview ), or upgrading your membership here though Paypal ( https://audiosciencereview.com/foru...eview-and-measurements.2164/page-3#post-59054 ).