Massdrop x Grace Design Standard DAC Balancedsearch
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Massdrop x Grace Design Standard DAC Balanced

Massdrop x Grace Design Standard DAC Balanced

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Stickied
Last year, Massdrop worked with Grace Design to set the new standard in entry-level objectivist DACs. Measurements and a price that beat OtherDACs…
With the success of the single-ended version and the release of our balanced amplifiers (Massdrop x THX AAA 789 & Massdrop x Cavalli Liquid Carbon X), the community has been asking for a balanced DAC.
Working with Michael Grace, Eben Grace, and Jamie Krapohl at Grace Design is always a real pleasure. From discussing potential features and learning technical considerations behind design choices to mocking up and fitting the I/O on the rear panel, specifying and developing the DAC with them is a special experience.
This new balanced version matches our balanced amplifier aesthetic, has a footprint compatible with our larger amplifiers as well as the Objective 2 amplifier, and is accessible- resetting the bar for performance and functionality for a standalone DAC at this price point.

What excites me about this one:
-People are going to love the USB connector :)
-Small enough to be very compatible with many different system set-ups
-How it looks on top of our THX or LCX amps
-All the stuff crammed into that back panel…making the dual 3-pin XLR fit!
-Coax SPDIF option (great for CD players or USB-to-SPDIF converters)
-USB 2.0 to support more filetypes, very high resolution
-Great for output into powered speakers while using digital volume control on your computer

I just keep checking out the back:
We’re waiting on the production pilot to produce the official graphs but we may share the development measurements soon.
There will be a couple of units floating around for some impressions in a couple of weeks…
DROP DETAILS
The drop starts Friday, August 17.
Shipping is free within the U.S. and reduced for international buyers.
We will be capturing payments at the end of August to get the production started.
Load 23 more comments
So can someone tell us how this confirmation from AKM relates to the use of the "dual channel" DAC for full differential output?

From my (rather ignorant) reading of this, it sounds like the DAC chip is outputting what is essentially a single-ended signal and then it is being split out into (psuedo?) balanced signal after that point. Is this a correct reading of this?
JeremyP
If I may, i didn't want to create a whole debate and it seems to confuse people, in effect I was just pointing that the differential output of the DAC chip doesn't tell any info if the output of the unit is Balanced or not. In fact it doesn't matter either they use both output to create a symmetrical and impedance matched pair to ground (a balance signal). The unit is not a preamp, not an amp, it's the very first stage of the analog audio chain so if the output is balanced it's a balanced DAC. the differential output of a dac chip matters if you connect it to something after it with a differential input A balanced output is different and it's not less balanced or pseudo balanced, it's balanced, regardless if they use both output of the chip or one. We can debate if something is truely a balanced design if it has analog inputs and outputs, we can then debate if the signal stays symmetrical troughout, if a XLR connector has just been put there for convenience, etc. but in this case it's just an output. You may be interested to know if they indeed used both polarity inverted output of the chip or if they used used a switched capacitor but there is not one method that is less balanced than the other. It's the very begining of a chain in a balanced configuration, and this balanced signal in all case is being generated after the chip. I was just pointing out that checking if the chip has differential output is not the right argument to say this DAC is fully balanced. In fact it can only be fully balanced or not at all.
Stickied
Hi All, Following is a bit of info on the new SDAC balanced. There is some description of the new features and circuitry, design intent, and preliminary measurement data.
The SDAC Balanced DAC is based on the digital to analog converter design in the SDAC. See my post on the SDAC which outlines the design philosophy and technical details and is all relevant to the SDAC Balanced: https://www.massdrop.com/buy/massdrop-x-grace-design-standard-dac/talk/1806625
(Please note my opinion on the role of the actual DAC chip in overall converter sound as I think there is much hype and judgment about which chip a product might use and how it will sound because of that choice.) Here I will discuss the addition of the SPDIF input, balanced analog outputs, and USB Audio Class 2 operation.
Here I will discuss the addition of the SPDIF input, balanced analog outputs, and USB Audio Class 2 operation.

SPDIF
Unlike asynchronous USB audio, a SPDIF (or toslink or AES3) signal contains an embedded clock that must be recovered by a receiver circuit. The quality of that recovered clock can vary widely depending on many factors. The design of the PLL (phase locked loop) used to synchronize the internal clocks for the d-a converter is critical to achieving high fidelity sound reproduction. The SPDIF receiver in the SDAC balanced is the AK4117 which is a solid performing hardware receiver circuit. The intrinsic jitter of the AK4117 PLL is not bad but since it is designed to acquire lock rapidly the PLL loop filter will not allow it to reject jitter in the audio band. For this reason we use a two stage clocking system with a second PLL that re-clocks the recovered clock from the AKM receiver. The second stage PLL is an extremely quiet digitally synthesized clock that has a loop bandwidth of 1Hz. This means that any incoming jitter on the SPDIF line that is above 1Hz will be attenuated dramatically to where it will not be able to produce any audible artifacts in the audio. To measure the effects of jitter on a DAC we send a relatively high frequency tone through the DAC and look for jitter modulated side bands in an FFT plot. I will upload a pictures of this that shows the output of the SDAC balanced reproducing an 11.025kHz tone with and without 1UI (177nS) of sinusoidal jitter. The SPDIF input is transformer-coupled for complete ground isolation. Note that the SPDIF interface maximum sample rate is 192kHz
BALANCED LINE OUTPUTS
The AK4452 DAC uses switched capacitor output filters (following the delta sigma modulator) which provide an inherently balanced signal at the output pins. From here, the balanced signal is sent to a fully differential output filter/driver amplifier. This amplifier has differential inputs and balanced outputs. Specifically this circuit is a fully differential multiple feedback 2nd order low pass filter with a Bessel response and a corner frequency of 100kHz. The fact that it is fully differential guarantees that the positive and negative phases leave the box with almost perfect amplitude matching (around +/-0.002dB). The Bessel response is chosen for the best phase response. The balanced outputs have a 300 Ohm output impedance (150 Ohms per leg) and produce exactly 2x the output voltage of the unbalance outputs at 4.34Vrms in to a 100k Ohm load. The unbalanced line outputs on the 3.5mm stereo jack operate simultaneously to the balanced outputs and put out 2.17Vrms in to a 100k Ohm load. All inputs and outputs feature robust ESD (electrostatic discharge) production.
A note on balanced vs. unbalanced signals: First of all, there is no inherent difference in fidelity between a balanced and an unbalanced signal. Under ideal conditions both signals can carry identical information. It is the factors of the real world where there we can differentiate (pardon the term!) between the two. As many probably already know, balanced line signal transmission with a differential receiver can reject common mode noise. The amount of rejection is known as the common mode rejection ratio (or CMRR). An unbalanced interface is prone to noise caused by ground potential differences between a DAC and a downstream device. This can be caused, for instance, by a setup where a computer is connected to a DAC via USB, the DAC is then connected to an amplifier, and that amplifier is connected to earth ground. If the computer is also connected to earth ground then you have a ground "loop" and current will flow through the audio cable ground between the DAC and amp causing noise. A balanced interface can reject that noise but the design of the balanced driver and receiver circuitry can cause degradation to the signal in the form of distortion and amplifier noise. So you see there is no black and white way to evaluate whether balanced is better or worse in a given setup. Ideally the DAC would have a galvanically isolated (ground isolated) USB interface which would break the "loop". Galvanically isolated USB is expensive and unfortunately not in the budget for the SDAC. So in this case, if there is going to be a potential for a ground loop, a well designed balanced interface can really help. The CMRR of the receiving device will determine how well it will reject noise.
USB Audio Class II
For those with high resolution files the SDAC Balanced will play PCM sample rates up to 384kHz and DSD 256 This is driver-less operation on Mac OSX and current versions of Windows 10. For older versions of Windows USB I mode is required and then sample rates will be limited to 96kHz. Here are some performance plots and measurements from our pilot build of SDAC Balanced DACs. These figures are actual measurements. Guaranteed performance specifications will be more conservative.






Frequency response @ 96kHz Fs: DC-20kHz +/-0.03dB Frequency response @ 129kHz Fs: DC-48kHz +/-0.4dB All distortion measurements are with a 22-22kHz bandwidth
THD+N% @ -0.15dBFS 44.1kHz
20Hz 0.0016
100Hz 0.0011
1KHz 0.0007
10KHz 0.0008

THD+N% @ -0.15dBFS 48kHz
20Hz 0.0018
100Hz 0.0012
1KHz 0.0008
10KHz 0.0007

THD+N% @ -0.15dBFS 88.2kHz
20Hz 0.0016
100Hz 0.0011
1KHz 0.0007
10KHz 0.0006

THD+N% @ -0.15dBFS 96kHz
20Hz 0.0018
100Hz 0.0012
1KHz 0.0008

10KHz 0.0006 THD+N% @ -0.15dBFS 176.4kHz
20Hz 0.0016
100Hz 0.0011
1KHz 0.0007
10KHz 0.0006

THD+N% @ -0.15dBFS 192kHz
20Hz 0.0018
100Hz 0.0012
1KHz 0.0008
10KHz 0.0006
Dynamic Range (A-Weighted) 115.4dB
Dynamic Range (Un-Weighted) 112.3dB Crosstalk @ 1kHz, -10dBFS -120dB Crosstalk @ 10kHz, -10dBFS -112dB IMD CCIF, -6.03 dBFS, 19/20kHz, 24/96k 0.00015% IMD SMPTE -2 dBFS, 24/96k 0.0012% IMD SMPTE -6 dBFS, 24/96k 0.0008% Linearity @ -90dBFS +/-0.025dB Maximum output unbalanced 2.17V Maximum output balanced 4.34V
Load 10 more comments
Unfortunately not. Win 10 and OSX only for the high sample rates...
Michael_Grace
Since Galvanically isolated USB is not possible at this moment, what would be your suggestions to those who wish getting the most out-of using USB?
Stickied
Greetings everyone, We have some excellent news! Based on community interest and feedback, we’re extending this drop by another 2 weeks. But not to worry, this will not extend the shipping date. We’re still aiming to deliver these products to you well on time.
We’ve also been listening closely to the discussions and we’ve identified an opportunity to make improvements to the I/O ports. Several members expressed desire in having additional options for digital input, namely optical input (TOSLINK). The Grace Design team has found a way to revise the PCB design to accomodate a single 3.5mm port that can handle both optical input and S/PDIF coaxial input using a 3.5mm-to-coaxial adapter. This is great because it won’t increase the manufacturing lead time nor will it affect the shipping date.
FROM: COAX SPDIF only
TO: 3.5mm combo jack- Optical SPDIF or Coax SPDIF (with an adapter)
3.5mm to RCA adapter:
Thanks again for joining the Massdrop x Grace Design Standard DAC Balanced drop. If you have any questions, please feel free to reach out to us.
Thank You,
The Massdrop Team
Load 7 more comments
As you can see, Toslink mini just fits 3.5mm size

So, end of Spdif jack has optical something also 3.5mm's side receives the Coaxial signal!
It's different with 3.5 mm Unbalanced Output at all!!! Only similar looking!
Hi ZOd1Ac,
The SDAC-B has TOSLINK (optical) and SPDIF (coaxial) inputs, not outputs. The adapter is to allow connections from an RCA phono type SPDIF cable to the 3.5mm SPDIF input jack. Connection to your powered speakers would be made via the analog unbalanced or balanced connections.
Cheers,
Michael
Is it possible to use this with the aune x7s to make a fully balanced path?
I really, Really hope this Amp have dual dac separated out put channel. I am aware dual dac can increase the production costs, and I am willing to pay like $250 to $300 for a good dual dac chips 32bit/384khz DAC.
This is massdrop, we are here to see some good products at reasonable price, not low end products at low price.
And yes, I understand that AK4452 comes with 5 types of digital filters, what would be the default choices? Any chance would there be like a dip switch to make them selectable? :)
AndyMok
That would be a fantastic feature.
AndyMok
The SDAC-B will ship with the linear phase sharp roll-off filter. This is the most versatile filter option and it ensures freedom from aliasing distortion on a wide range of program material.
This is the same filter used in the SDAC.
Will 2 of them match the Massdropp THX AAA headphone amp in width?
rajapruk
The SDAB-B dimensions are:
104.6mm W x 31.5mm H x 105mm D
Height with the screw on feet is about 36mm
Is the unbalanced version dropping anytime soon?
Please do better Massdrop. I love what you guys are doing in regards to affordable audio but as of late some of these DAC and amp drops leave a lot to be desired with the ridiculously long delivery dates and next to no information. Moreover you have to see that things like this might turn eager buyers completely off.
Hi All,
Sorry to be absent from this discussion so far. We have been really busy in the lab working on bringing the balanced SDAC to life. While at its core it is based on the SDAC there was much new development involved in its design.
We are finishing up the design qualification testing today and I will be able to post some performance measurements and answer questions about this new DAC shortly.
Cheers,
Michael
Will this be made in the US?