MEASUREMENTS: Topping D10 DAC. (And a few words on "absolute polarity / phase".)

Hey guys, getting busy around here as I'm preparing for summer holidays coming up in a couple of weeks :-).

I did want to post a "quick" report however on the Topping D10 DAC (<US$90) I got last week... It's for an upcoming project of sorts which I'll post on over the months ahead. What I wanted was a DAC that could be powered off USB, reliable with Window and Linux compatibility, that's reasonably portable, and of course of high signal accuracy.

Notice the DAC manual shows some AP measurement graphs... I guess Topping believes in showing objective accuracy :-). Nice.

As some of you will likely already know, this DAC was measured by Amir at Audio Science Review initially back in the Spring of 2018 using his Audio Precision gear and more recently updated with March 2019 results here. Looks good. I did some measurements to confirm good performance with the unit I received so the results here will hopefully touch on a few items I haven't seen and show a few of the tests I typically perform here on the blog that may not be shown elsewhere...

For the tests here, I'll just be using my previous Focusrite Forte ADC. In part this is because for some upcoming testing, plus the portability of the Focusrite Forte is important even though it's not as capable as the RME ADI-2 Pro FS I've been using over much of this past year.

The Topping is a small, but relatively handsome all black DAC with sturdy metal case, and featuring a good sized front LED. It's capable of up to 32/384 PCM and DSD256 playback. The DAC is based on ESS Tech's ES9018K2M chip and XMOS XU208 USB2.0 interface. On the back are the USB-B input which also powers the machine, both coaxial and TosLink S/PDIF digital outputs are available, plus the unbalanced analogue RCA output of course. I have not used the digital outputs yet so can't say if both the coaxial and TosLink can both handle 24/192 (most modern DACs these days can manage TosLink 24/192 in my experience), nor examined the jitter out of these interfaces.

I've been running the D10 fed with my Raspberry Pi 3 using piCorePlayer streaming off Logitech Media Server. Setup was straight forward and no compatibility issues thus far, and I've streamed up to 24/384 without issue. The measurement chain looks like this:

Raspberry Pi 3 (piCorePlayer), WiFi, 5V lithium battery powered --> shielded USB --> Topping D10 DAC --> shielded 6' RCA --> Focusrite Forte ADC --> Win 10 laptop (battery powered)

As you can see, the whole measurement chain is battery powered. The Focusrite Forte ADC is run off the laptop itself. The Raspberry Pi 3 and Topping D10 are both powered off a RAVPower 22000mAh lithium power bank which can easily run the unit for hours on end.

Let's see some signals through a digital oscilloscope:

1kHz 0dBFS sine and 1kHz -3dBFS non-ringing square 24/44.1.

It looks pretty good. Nice right-left channel balance. RMS output of 1.5V from the RCA connectors. Square wave suggests symmetrical linear phase digital filter. Indeed, that is what it is:

Notice that the impulse is inverted. Not a problem unless you're a strict adherent of "absolute polarity". We'll talk more about this later.

Let's overlay a few FFT graphs to look at that filter in more detail (this is the "Digital Filter Composite" [DFC] graph I often show on this blog site, based on Juergen Reis' work)...

What this tells us is that the filter can handle intersample overload even with the 0dBFS wideband white noise (this generally means it can handle +3.01dBTP material just fine). Filtering is also reasonably steep with essentially no imaging distortions from the 19 and 20kHz tones. Some harmonic distortion but at least 90dB below the primary signals in the ultrasonic frequencies. This is a good looking DFC graph for a DAC's built-in filter.

Okay, let's now have a look at the RightMark battery of tests with some comparative results...

24/96:

Note: Although not in the label, the TEAC UD-501 was using XLR output.


Note: TEAC UD-501 using XLR output.

24/192:

Overall the Topping D10 DAC compares favourably to the other devices, including some much more expensive DACs like the old Oppo BDP-105 and my TEAC UD-501. Notice that the noise level of the Topping was subtly higher than the others but what is impressive are the excellent THD and IMD results. In this field of comparison devices, only the TEAC UD-501 24/96 with XLR outputs approached the THD result from the Topping. Obviously if I measured my newer and better DACs like the Oppo UDP-205 and RME ADI-2 Pro FS with balanced output, these would be superior.

The two less expensive DACs - the HiFiBerry DAC+ Pro (HAT board) and SMSL iDEA performed significantly lower in regards to distortion even though noise level from these DACs were slightly lower.

The low distortion results are exactly what I needed for the measurements I wanted to perform which will be discussed in the near future.

I ran into troubles trying to plot the frequency response of the different devices at 192kHz so I just showed the frequency response of the Topping D10 alone instead. We see that the high frequency extension goes out to ~72kHz by the -3dB point, and about 83kHz at -6dB; of course at these ultrasonic frequencies, the Focusrite Forte ADC itself could be the limiting factor. Comparative noise levels could still be plotted without issue with device overlays, again demonstrating the slightly higher noise floor of the Topping.

Finally, here are the J-Test graphs:

While we see some low-level jitter in the 16-bit result below the jitter modulation tone, it is in the 24-bit J-Test that they're more evident as symmetrical sidebands. Note though that these are very low amplitude products - something like 130dB below the primary signal.

Jitter's interesting when found, but these are trivial amounts and nothing close to being audible! (Remember to put the whole jitter "issue" into context by examining and listening to some simulated jitter samples.)

In conclusion...
For <US$100, one can get some very capable high-fidelity DACs these days from the various "Chi-Fi" brands like Topping or SMSL. No surprise given that most high tech manufacturing comes from China these days including your latest and greatest iPhones et al...

The Topping D10 DAC sounds clean and tight when I hooked it up to the main system over the last few evenings (Emotiva XSP-1 preamp, Emotiva XPA-1L monoblocks, Paradigm Reference S8 speakers) for some music listening. Though I heard that the movie wasn't all that good, the X-Men: Dark Phoenix soundtrack from Hans Zimmer is highly reminiscent of the Interstellar soundtrack if you like that kind of hard driving, bass-filled, aggressive sort of sonic affair! Unfortunately this "kind" of sound also generally means dynamic range compression these days and the album shows a DR9 result.

Speaking of soundtrack music, I recently was reminded of the Finding Forrester (DR11) and had a listen using this DAC. A nice sounding sampling of jazz including "Iz" Kamakawiwo'ole's version of "Over the Rainbow / What a Wonderful World", plus a selection of Miles Davis for those who want a convenient mix playlist on one CD... Nice separation of instruments, good soundstage through the Topping D10, I can't complain.

I also had a listen to Morgan James Live from Dizzy's Club Coca-Cola: A Celebration of Nina Simone (DR9). Good sounding live female vocals - very audiophile-friendly :-). Lots of detail off this DAC with nice ambiance from the live setting coming through. Good tonal reproduction without any unexpected or excessive sibilance. The little noises and clapping from the audience members sound detailed and well placed.

As you can see from the measurements, this DAC performs with very low distortion performance. It might give up a dB or two in the noise-floor and stereo crosstalk departments compared to more expensive devices, but otherwise IMO you're not missing anything. Notice that the DAC has no buttons or any kind of hardware configuration. It's simply a no-nonsense asynchronous USB DAC providing good single-ended RCA output that delivers technically accurate performance down to the textbook linear phase digital filter (my preferred setting), and will cover a wide range of PCM and DSD samplerates - likely more than we'll ever need. No nonsense like MQA of course.

The only thing unusual about the DAC was the inverted polarity (or "phase") mentioned above. While I would have preferred that the polarity were not inverted (ie. a positive deviation in the audio editor resulted in the same positive deviation at the DAC output), this isn't really an issue IMO. In fact, if you're a computer audio user, it's quite easy to "fix" this; a number of the popular programs can do it... Here are JRiver and Roon's settings for example:

Can select that polarity can be inverted depending on the channel... Make sure to invert polarity for both left and right of course.

I know that the significance of "absolute polarity" can be a bit contentious with some audiophiles claiming they can hear it and others can't. I've tried over the years and cannot meaningfully hear a difference with various headphones and good quality speaker systems. While you can read opinions from various audiophiles, make sure to also check out this forum thread for discussions from the pro/studio audio folks. Remember that in the albums we buy, there is no assurance that a studio will follow a standard in the music one way or the other.

Let's think about this. Remember that sounds are waves; the impulse response I use to easily demonstrate polarity is actually an "illegal" signal and not an actual sound one should ever "hear" in a recording. In order for us to actually hear waves at any given frequency, we need to experience both the compression and rarefaction for a period of time in order for the brain to experience the event. Does it really matter if that very first motion of one's speaker/headphone transducer pushes the air forward or pulls the air backwards when one actually needs a few of those vibrations to register the "sound" experience? I suppose in the very low frequencies, the appropriate initial "push" of air from a deep bass drum might be experienced as more "right" although I personally have not experimented with this. [UPDATE: See the next blog post on "absolute polarity" discussing and clarifying comments...]

I think J. G. Holt's assessment back in 1980 "Absolute Phase: Fact or Fallacy?" is worth reading. As explained, likely the most significant difference that may be heard when flipping between polarity settings is when the transducer (or even the amplifier) is nonlinear and functions asymmetrically. The asymmetry would result in playback distortion; this is bad and suggests a playback system issue. If so, it's then important to keep in mind that if one were to hear a big difference "flipping the polarity switch", could it be that the amplifier/transducers you're listening to may be of poor quality? (Rather than the idea that one has found the "right" setting for the music itself...)

Remember that multi-way speaker systems often have drivers set up in opposite polarity, so the idea of an "absolute" here might not even exist for one's system and it can depend on the frequency of the sound itself which "way" the air is being pushed.

Anyhow, since I guess I can't generally seem to hear this polarity issue and/or the speakers I use are "linear enough", there's nothing I can do to explore/test this further. I suppose we could set up some kind of Internet Blind Test and see if in a blinded state, the audiophile community out there can come to consensus with a few demo tracks of which sounds "better"...

I'd love to see any research references on the "audibility" of absolute polarity. Drop links / references in the comments below if you know of some...

Regardless, for my purposes which will become evident ahead, the Topping D10 sounds very good and work just dandy. :-)

[***Note: for those who bought the D10 awhile back, make sure to update to the newest firmware v1.02 (18l) for some bug fixes.]

Have a great week ahead... Hope you're all enjoying the music as we head into the summer holiday season here in the Northern Hemisphere.