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Grace Design m903 Async USB To 192k

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Thanks Chris for the heads up!


Interesting to see that more and more companies take care of USB as a "high quality" input.


That and the upcoming Mytek and Audiolab units will bing a lot of fun and quality "bang for the buck".


The following feature got me smiling

"Mono mode for checking mix phase issues (or listening to Pet Sounds)"





Esoterc SA-60 / Foobar2000 -> Mytek Stereo 192 DSD / Audio-GD NFB 28.38 -> MEG RL922K / AKG K500 / AKG K1000  / Audioquest Nighthawk / OPPO PM-2 / Sennheiser HD800 / Sennheiser Surrounder / Sony MA900 / STAX SR-303+SRM-323II

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  • 3 weeks later...

products usually feature discrete output stages, and sound quite different from Benchmark. I suspect this unit will offer highly resolved sound, with a touch of warmth and bloom, as well as more accurate instrumental timbres. It is really cool to see these guys using the "Streamlength" code.

BTW, I believe that Michael Grace has an audiophile background, as he used to work with Jeff Rowland before starting his company.


SO/ROON/HQPe: DSD 256-Sonore opticalModuleDeluxe-Signature Rendu optical--Bricasti M3 DAC--DIY Purifi Amplifier-Focus Audio FS888 speakers-JL E 112 sub-Nordost Tyr USB, DIY EventHorizon AC cables, Iconoclast XLR & speaker cables, Synergistic Purple Fuses, Spacetime system clarifiers.  ISOAcoustics Oreas footers.                                                       

                                                                                           SONORE computer audio

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in the digital or analog section? From the specs "Balanced and unbalanced variable level analog line outputs" looks like it, but am unsure.


I was keen on the m902, but with the USB to 48 (adaptive?) marked it off my list about 6 months ago. The m903 with Streamlength has put the DAC on the front burner again up the list, just about on top!

Sweetwater and Vintage King have the m903 listed with prices.



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Any news on getting one to review? This is interesting! I'd love to see a shootout type comparisson between several DAC's in the 1500-2000 range.... This one, w4s dac2 etc....


Thanks for pointing it out and all your great work on this site!




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  • 1 month later...

Chris and 1 &1/2..


Nice one.


Mr Grace mentions this as powering studio monitors.

Could this also be a suitable Dac/pre for hifi poweramps?

Also keen to here what volume control technology this things has :)






New simplified setup: STEREO- Primary listening Area: Cullen Circuits Mod ZP90> Benchmark DAC1>RotelRKB250 Power amp>KEF Q Series. Secondary listening areas: 1/ QNAP 119P II(running MinimServer)>UPnP>Linn Majik DSI>Linn Majik 140's. 2/ (Source awaiting)>Invicta DAC>RotelRKB2100 Power amp>Rega's. Tertiary multiroom areas: Same QNAP>SMB>Sonos>Various. MULTICHANNEL- MacMini>A+(Standalone mode)>Exasound e28 >5.1 analog out>Yamaha Avantage Receiver>Pre-outs>Linn Chakra power amps>Linn Katan front and sides. Linn Trikan Centre. Velodyne SPL1000 Ultra

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  • 3 weeks later...

Well..the m902, the predecessor can supply some 7.52V (1kHz) coming from a source impedance of 47Ohms, this is more than enough to drive a power amplifier directly. Volume control is analog, since the M902 & m903 have analog inputs, so it makes sense to keep the volume control in the analog domain.


Here's a review of the m902:



The big difference between the m902 and m903 is 24/192 USB class 2 audio using Streamlength implementation. There's a lot more decriptions about the changes on the Grace website.


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  • 1 month later...

The m903 *finally* arrived, spent most of last night running through the DAC's paces into the wee hours.

First impressions tend to last, and the impression on this DAC is it sounds as great as it looks. Very easy to configure, takes a little getting used to, especially the controls and deeper functions, but if you use an iPod, or a newer style microwave oven with a rotary encoder, you won't have any steep learning curves.


I used a pair of Vovox TRS to XLR cables to the balanced input on the Accuphase E-450 amp. Starlight mini USB to the MBP, although Grace Design provide a USB cable. For comparison, kept the Halide bridge and the DAC-20 in place, and used PM to select either hardware to listen to.


Pumped a 1kHz sine wave into both DACs to set the level on the amp to be the same, the value of 88 on the encoder was the right volume. I can confirm, the volume control on the m903 is analog, which put a smile on my face.


The m903 has two frequency settings for USB, u1 and u2. u1 converts up to 24/96, and u2 24/96 to 24/192. On the face of this, it would appear that you need to use u1 for Redbook and 96 material, and u2 for higher frequencies, a bit odd.

If you do use u1, the DAC uses USB Class 1 Audio conversions, and here the head started to scratch. The SQ from this mode compared with the DAC-20 was similar to compare iTunes raw and adding PM or Amarra.

Cymbal decay was far too short, bass is a sloppy, mids sound very mushy. It's not to say it's terribly distorted, but there is better out there.


So, what does u2 setting do? Aha! The genie is out of the bottle now, USB Audio Class 2 in its full glory, and does it sound saweet! Rock solid instruments, excellent timing, the smear is gone from the u1 setting, the breathing vocals are back, you can hear Eiji Oue rustle his coat and tails in Copland's Appalachian Spring, just astounding.


After this discovery there was no turning back to Class 1 setting. u2 works for Redbook, 24/96, sounds stunning and no oversampling!!! The LEDs light up according to the tracks frequency like they should for bit perfect playback. Works out of the box, other than to set the output level, and how to boot up the DAC to that level is about all the setup there is.


Haven't noticed any need for burn in so far. Down the track will compare the USB cable with the Starlight. I rate this DAC 4 1/2 stars, well designed and hats off to Grace Design and to Gordon Rankin for Streamlength technology, which really delivers the goods.


Thoroughly recommend this DAC for Class 2 Audio, playing back 24/192 without using special drivers makes this concept and DAC last for many years of pleasurable listening to come.


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Since I designed the U1, U2 code let me explain.


Class 1 is available on almost every OS and does not require any driver and is available to 24/96 Full Speed (U1).


Class 2 is available on OSX and some Linux platforms but NOT Windows and works at speeds above 24/96 (U2) or 24/192 in this case.


If you are running OSX or a Linux that is capable of Class 2 or use the custom Windows drivers then leave the setting at U2.


If you don't want to use the Windows drivers or your Linux box does not support Class 2, then set the output to U1.





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Many thanks to one and a half for his very interesting review of the much awaited M903.


To Gordon, thanks for the explanation on U1 and U2. I would like to ask you if there is any explanation why U2 work so much better than U1 for standard cd quality? Would it also work better with Pc using your custom made driver,(since I am, for the moment, a PC guy)?

Thanks in advance for your answer,





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I'd like to hear Gordon's comment on that as well.


While I'm at it. Gordon. Please make a headphone amp!


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To Gordon, thanks for the explanation on U1 and U2. I would like to ask you if there is any explanation why U2 work so much better than U1 for standard cd quality? Would it also work better with Pc using your custom made driver,(since I am, for the moment, a PC guy)?


Well probably because the Thesycon driver we use for Class 2 is better than the built in Class 1 driver that Microsoft delivers.






Me too... but I don't have the time. Maybe a 45 based directly heated triode unit with built in int input. I do have transformers for this now, just have to find the time. Or maybe the 71A with a simple 12AU7A input scheme may work really well. hummmmmm





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Not being used to a headphone amp, I can't make any major comparisons. However, compared to an integrated amp's headphone output, the m903 against the Accuphase, well, there's not much in it at all, and it's very difficult to hear differences, so I gave up.


Róisín Murphy's 'Let me know' is very tight, being all synth, each instrument is very clearly defined, no muddiness, no colorations.


Eagles, 'Last Good Time in Town' has many instruments, some I have heard for the first time on the m903, kinda exciting! Both circumstances used the u2 setting.


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I'm hoping someone can verify whether or not the two outputs are both RCAs, and whether it is possible to use them in a bi-amping configuration? It appears from the photo that outputs are an either/or, but not both proposition...



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