Massdrop x Grace Design Standard DAC
Massdrop x Grace Design Standard DAC
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Product Description
Made in collaboration with Grace Design, a company known for its incredibly accurate, transparent studio gear, the Standard DAC sets a new standard in entry-level DACs. It applies Grace Design’s pro-audio expertise to a simpler, more accessibly priced model that makes a great addition to any home or office system ... Read More

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Michael_Grace
372
Grace Design
Sep 7, 2017
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Hi All, I thought I would provide some technical details about the SDAC design that are not evident by reading the specifications. When Massdrop approached us to design a USB DAC that could provide equal or better performance than the ODAC Rev B or Schitt Modi 2, but be more affordable than our m9XX, we jumped at the challenge. The SDAC contains mostly new circuitry for us and there was not much we could reuse from previous products we have built in the past. Successful DAC design begins with the understanding that a DAC chip is in essence a mixer. The output from a DAC is a mix of four primary inputs: 1) Digital audio data 2) Clock Jitter 3) Power supply noise 4) Analog circuit distortion. Modern delta-sigma DACs have vanishingly low noise and distortion so the "sound" of a DAC is really less controlled by the actual IC selected for the design and more by the quality of the clock, power supply, and analog amplifiers. Also, to a lesser but significant degree, passive components like capacitors and resistors in the analog signal path. The SDAC employs asynchronous data transfer from the USB host, which allows for the use of fixed crystal oscillators rather than phase locked loops (PLLs) or digital clock synthesis. A low noise fixed crystal oscillator is the lowest jitter sample clock and there are two in the SDAC: One 22.5792MHz crystal for 44.1kHz and 88.2kHz sample rates, and one 24.576MHz crystal for 48kHz and 96kHz sample rates. These are located very close to the DAC. I should note that asynchronous mode allows for the use of a high quality clock but it is not intrinsically better. It is certainly possible that there asynchronous designs out there that use low grade clocks and therefore are not benefiting from asynchronous mode. The power supply for the DAC is designed for very low noise and good noise rejection. This is critical to the overall performance and is not easy to do given the constraints of USB bus power operation. There are separate voltage regulators for the DAC, processor, and analog circuits, which minimizes interaction between these circuit areas. The analog output circuits are based on very low noise and low distortion amplifiers. With harmonic distortion below -120dB, they are well below the distortion floor of the DAC. The SDAC is direct coupled with no capacitors in the signal path, which gives low frequency response that is perfectly flat and free of phase shift. Following is a list of some of the technical features of the SDAC:
  • XMOS X200 USB streaming controller operating in asynchronous transfer mode.
  • IDT XLH series oscillators provide and exceptionally stable and low noise sample clock for DAC. 12kHz to 20MHz phase jitter is 750fs. Note that the jitter below 12kHz is generally more important in audio applications but the 12kHz-20MHz specification is commonly used for specifying oscillators so it is useful in comparing to other clocks. In the SDAC the clock jitter artifacts are well below the DAC noise floor so they are essentially irrelevant.
  • AK4452 DAC provides 32 bit internal processing , 115dB dynamic range, and the same architecture as the AK4490.
  • Output amplifiers are Burr Brown OPA1652. These are extremely low noise low distortion FET input amplifiers with excellent output cable drive capability. Note that the output impedance is set at 150 Ohms so the SDAC is not intended to drive headphones. While it will not harm anything to do so, the fidelity will not approach what is possible with a good headphone amplifier.
  • The negative audio power supply is generated with a switched capacitor circuit that operates synchronously to the audio sample rate to eliminate any possibility of power supply related spurs in the output spectrum.
  • DAC power supply is regulated with the TPS793 low noise linear regulator to reject any contamination from noisy USB power.
  • 4 layer FR-4 circuit board with careful attention to high speed digital layout, power supply grounding, and low noise analog signal routing.
I will attempt to upload a fft plot showing the SDAC passing a 10kHz sine wave. Notice that there are no visible jitter sidebands (spurs that appear evenly spaced on either side of the fundamental tone). The line at 20kHz is the first harmonic at -92dB. The level of the noise floor suggests that the upper limit of random jitter in the SDAC clock is around 1.5ps at any given frequency. If anyone has questions let me know. I will try to check in here as time permits... Cheers, Michael
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Sep 7, 2017
Michael_Grace
372
Grace Design
Jul 15, 2019
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This should be no problem at all! Keep in mind though that some headphone amplifiers, depending on their input circuitry, can actually cause a little distortion in the output of the SDAC if being driven with the power off. So you might just do a listen test with the unused amp on and off to see if you hear a difference. Cheers, Michael
Jul 15, 2019
Graham43
15
Jul 16, 2019
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Thanks Michael. I will have the Little Dot Mkii on the RCA output and the JDS Labs Atom amp on the 3.5mm output of the DAC. I will do a listen test as you said.
Jul 16, 2019
JJLKalkaska
1
Jun 27, 2019
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I am trying to replace the included USB cable for a shorter one, but it isn't recognized unless I use the original cable. Is there any reason this is happening?
Jun 27, 2019
jacksonnash
1
Jun 13, 2019
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I can't seem to get the DAC to be recognized by my computer, any suggestions?
Jun 13, 2019
MananaMan
60
Jun 6, 2019
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I NEED this right NOW please reopen the drop :))))
Jun 6, 2019
verifonix
614
Jul 19, 2019
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well its reopened, in stock.
Jul 19, 2019
MananaMan
60
Jul 19, 2019
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ah but its the balanced dac thats twice the price of the original :((((((( i just wanted to use the atom amp which is unbalanced so its pointless to get a balanced dac :(((((
Jul 19, 2019
PedroTaboaco
1
May 20, 2019
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I want to use only one cable to connect my iPad Pro to the Massdrop x Grace Design SDAC, if possible. Can anyone give me the technical specs to buy the correct cable? Any brand / model recommended? Thank you!
May 20, 2019
shadowkreep
501
Apr 20, 2019
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@Michael_Grace Do you have any idea if this drop will be available again in the near future? I'm new to the scene and missed out on this stellar piece!
Apr 20, 2019
Duks
2
Apr 20, 2019
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A newbie question: can you use this for active speakers/monitors, and how do you use it with headphones? (using a PC) Thanks.
Apr 20, 2019
NeoTheLizard
79
Apr 20, 2019
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Don't have that much experience with speakers, but as far as i understand, yes, you can. Whether using it with speakers or headphones, it's mostly intended to be hooked up to a dedicated amplifier using the RCA outputs at the back. In the case of headphones, you then plug your headphones into the 3.5mm or 6.3mm audio jack of your amplifier.
Apr 20, 2019
Tasunke
15
Apr 11, 2019
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Received my DAC today and luckily my amp too. Works great for me. The stack sounds amazing (upgrading from the onboard soundcard of a high-end motherboard). Now for a new pair of can, undecided betwenn Sennheiser's 660S or Beyerdynamics DT 1990 or Amiron Home.
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Apr 11, 2019
Seijuro
13
Apr 14, 2019
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660s all the way unless you like Beyerdynamic treble. 660s can also be found for much less money.
Apr 14, 2019
Tasunke
15
Apr 15, 2019
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I'm a Beyerdynamic fan actually, currently using 770. Not treble sensitivity at all. Sennheiser's are in the mix only because of their overwhelmingly positive reviews and being in the same price range. Only tried low tier Sennheiser, so harder to make an idea. And finding a shop with all of them avalaible for testing is a PITA in Switzerland arround Geneva.
(Edited)
Apr 15, 2019
apastuszak
48
Apr 10, 2019
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SDAC has been disconnect and ODAC is back in place. This thing DOES NOT like Windows 7. I've had to reboot 5 times today already. That's 5 times too many. Sadly, this is a work computer and I am stuck on Windows 7 through the end of the year.
Apr 10, 2019
shadowkreep
501
Apr 20, 2019
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If you're looking to part with it, i would gladly make an offer :)
Apr 20, 2019
apastuszak
48
Apr 24, 2019
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Massdrop sent a replacement, and the new one is working much better.
Apr 24, 2019
apastuszak
48
Apr 10, 2019
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The SDAC is giving me no end of hell under Windows 7. At some point the sound system crashes and takes Skype for Business with it and the only way to get it back is to reboot my computer. Anyone else seeing this? There was discussions of this issue on the O2+SDAC and one of the solutions was to plug it into a USB 2 port. Well, I did that, and it didn't help any. Anyone experiencing this or have a possible fix?
Apr 10, 2019
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