Saturday, 27 June 2020

MEASUREMENTS: Topping DX3 PRO V2 (LDAC version) - plus frequency/amplitude stepped sine measurements, a quick look at the 8kHz USB PHY packet noise, and AirPods Pro "Spatial Audio" coming...

So I got another DAC here at home - purchased through usual retail channels of course :-).

The Topping DX3 PRO (~US$220) is a device meant for those who want wired (S/PDIF TosLink, Coaxial, USB) as well as flexible Bluetooth 5.0 wireless input. There are 2 versions of the DX3 PRO out there - the earlier version reviewed/measured at Audio Science Review by Amir and the newer one which I have here with LDAC support (Sony-developed "high resolution" Bluetooth CODEC, also measured by WolfX-700) released in late 2019.

At some point, I figure it would be interesting to compare how the various Bluetooth codecs perform since this device can accept the lowest common denominator SBC, plus AAC, aptX, aptX-LL (Low Latency), aptX-HD, and LDAC audio - about as broad a range as I've seen among Bluetooth DACs (here's a good primer on these acronyms).

For today, let's examine the device's standard DAC performance and run it through my typical procedure with a few new measurement variants to see how it performs.

I. The Box

Here's a top view of the box with the antenna sticking up - notice the "Hi-Res Audio" stickers - one for the standard hi-res DAC, another for the aptX-HD and LDAC wireless hi-res.

It's a pretty nice solid metal box. Plastic remote with a good clicky feel to the buttons. Here's a picture of the remote with the rear of the DAC:

Notice that there are 2 S/PDIF coaxial, and 1 TosLink digital inputs. Regarding the remote, while light weight, the buttons are responsive. Right/left buttons to change input. The "M" button switches from 0/+9dB gain on the headphone amp. "FIR" for filter options. "M" for toggling auto-standby if not in use for a few minutes or no input signal.
A small switching 15V/1A wallwart power supply is included of course. Notice that it only has unbalanced RCA outputs at the rear with a 3.5mm headphone jack out front. I believe 3.5mm jacks are more convenient these days for most home users than 1/4" jacks although I do find 1/4" more robust if we're going to call this a "PRO" product. The output setting is quite flexible with choice of RCA +/- headphones active. Also, the RCA out can be set as direct line out or pre-amp mode with volume control which is a nice touch.

The DAC uses dual AKM "VelvetSound" AK4493 chips for conversion (spec of -113dB THD+N / 126dB DR). XMOS XU208 USB controller to handle up to DSD512 (DSD256 DOP) and PCM 768kHz. Qualcomm CSR8675 Bluetooth chip to support the various audio codecs. Remember that Qualcomm purchased CSR, the makers of aptX back in 2015 so it makes sense that this chipset supports the range of aptX flavors. Headphone out amplification uses the TI TPA6120A2 (spec -112.5dB THD) with 0dB and +9dB gain settings available. The spec says up to 700mW into 32Ω load. Given the price, this is a capable DAC.

The older V1 model used the TI OPA2140 opamp to drive the headphones.

Similar to the Topping D10 previously measured, the manual comes with some measurements already printed for you - nice to see, audiophiles need not be phobic over numbers and charts :-)

Nice OLED display - easy to read volume control setting. Topping D10 on top.

II. Oscilloscope Waveforms, Digital Filters, Headphone Out

As usual, let's start with the "microscopic" tests. Right off the bat, we see that this DAC provides us with a number of digital filter options. To be honest, while it's nice to have choices, unless I'm purposely fooling around with stuff like the custom intermediate filtering, I'll listen with standard linear phase, steep filters. Typically these provide best flat frequency extension and the linear phase setting will not add phase shift/group delays in the time domain.

For the DX3 PRO, this means filter setting F-1 (labeled as just "F1" in my diagrams) would be my focus for the majority of these measurements and when listening. So with the DAC set at F-1, this is what a 1kHz 0dBFS sine wave and -3dBFS square waves look like off the rear RCA outs (connected by USB from Raspberry Pi 3 B+ running Volumio):

As you can see, the output is a standard 2.1Vrms at 0dBFS. Channel balance is excellent with the 2 channels precisely overlaid in the sine waveform. For the square waves, as expected, with the filter set at linear phase, pre- and post-ringing are symmetrical.

So, for filter F-1 setting, the impulse response looks like this:

Note that "absolute polarity" is maintained. Here's the "Digital Filter Composite" (DFC) consisting of an overlay of various signals that can help us understand the digital filter better in the frequency domain, based on discussions with Jürgen Reis. This is an extension of what Stereophile has been doing:

Looks great; for context, compare this to the AudioQuest Dragonflies. The filter is reasonably steep with minimal imaging artifact from the 19 & 20kHz tones or wideband white noise. Already we can see that IMD would be quite low. Furthermore, this filter has enough intersample overload protection to prevent anomalies with the 0dBFS white noise signal. Certainly an excellent performing digital filter among the DACs I've evaluated over the years.

This is of course just filter F-1... The DAC provides 6 settings total, here are my descriptions rather than using the AKM or Topping language which can be a bit vague:
     F-1 = Linear Phase, Sharp Roll-Off
     F-2 = Linear Phase, Slow Roll-Off
     F-3 (Default) = Minimum Phase, Sharp Roll-Off
     F-4 = Minimum Phase, Slow Roll-Off
     F-5 = "Super Slow" Roll-Off - essentially non-oversampling
     F-6 = "Low Dispersion", "Short Delay" - Intermediate Phase

I didn't bother testing them all with DFCs, but here are the impulse responses for F-2 to F-6:

For the most part, the filters are as per the descriptions. Of interest, the F-5 setting is useful if you want to listen for a NOS-like sound. I'm not even sure why they call it "Super Slow Roll-Off" - it's essentially unfiltered! And the F-6 "Low Dispersion" is an intermediate phase setting with moderate steepness.

Since F-3 is the default and I assume many people will just listen with that setting, here's the DFC graph:

While the steep roll-off is the same as F-1 above, notice that it doesn't handle "intersample overs" as well and we can see this showing up with the 0dBFS wideband white noise signal.

As I said above, for those who love the sound of Non-Oversampling DACs, Audio Note's silly misnomered "1x oversampling", stair-stepped waveforms, or the "euphonic distortion" that this might bring with copious ultrasonic imaging/"aliasing" artifacts, check out setting F-5 and this "beauty" of a DFC graph and stair-stepped 1kHz sine wave:

The headphone output is indeed quite powerful. It's capable of pushing 4.6Vrms into a 30Ω load at the +9dB gain setting (filter setting F-1):

So that's a good 700mW as per spec. The one disappointment however which the WolfX-700 measurement/review found was that the output impedance unfortunately is rather high:

That voltage drop from Open to a 30Ω load (1kHz sine) calculates out to an output impedance of 10.4Ω. The specs sheet rated the headphone output impedance as "<10Ω". Yeah, this definitely could be better and suggests that one should use higher impedance headphones to reduce variation in frequency response (80+Ω). The previous DX3 PRO V1 was superior with a measured output impedance of 1Ω. Remember guys and gals, just like amplifiers with higher output impedance, ears/brains are forgiving and sticking a 32Ω IEM into this DAC still can sound good depending on the headphone even if technically suboptimal.

III. RightMark noise and distortion results

Okay, let's now run the DAC through the battery of tests in RightMark Audio Analyser 6.4.5 Pro. As usual, the standard measurement chain I use these days is with the RME ADC:
Topping DX3 PRO V2/LDAC --> Generic 6' RCA cable --> RME ADI-2 Pro FS ADC --> 6' Generic USB --> Microsoft Surface 3 Pro computer for analysis
For these measurements, I've set the filter to F-1. As I said above, I like "orthodox" linear phase, steep roll-off filters for listening and measurements.

Other than listening for a few hours before measuring (maybe 4 hours total) to make sure all features worked, no "burn-in" is needed. Over the years using audio electronics, I've certainly heard "warm up" change sound quality, "burn out" of components (smoked some amps over the years), and "break down" resulting in distorted sound... But other than maybe mechanical changes over time like speakers settling in, I have never heard "burn-in" actually improving sound quality over hours and hours of use.


Starting with standard resolution, let's just make sure there are no surprises with the DAC - here's the summary results with a few other comparison DACs:

Not bad at all for the Topping DX3 PRO, with RCA output. As has been the case for years, standard CD-resolution reproduction is no problem with essentially any decent DAC. This is consistent with the blind test results last year as well.

Performance is essentially the same at 16/44.1 compared to the inexpensive Topping D10 (currently ~$US90) although marginally better THD and IMD+N can be seen. The TEAC UD-501 was my reference DAC for many year purchased in 2013. The Oppo UDP-205 has since become my daily use reference DAC for the main system since I got it in 2018. For "fun", I've included the venerable PonoPlayer that I got back in 2015 as well as the inexpensive SMSL iDEA (the equivalent Sabaj Da2 can be had for <US$60 these days).

Here are some graphs for more details:

Notice that the PonoPlayer rolls off the highs due to its slow-roll filter at standard resolutions similar to the minimum-phase Ayre "Listen" filter. The noise level graph shows that the TEAC UD-501 and Oppo UDP-205 have a little bit of 60Hz mains hum (absent if you use the XLR balanced output). Notice that the Topping DX3 Pro does not have hum with its little switching power supply.

The Topping DX3 Pro IMD+N suggests a device with very low non-linear distortion across the audible spectrum.


It's with the 24-bit high-resolution tests that we typically see more measurable variations between otherwise good DACs. Here's a summary with the same selection of devices:

This is where we see the DX3 Pro pulling out ahead of the D10 in resolution. In fact, for RCA output, the dual AKM AK4493's are essentially as quiet as the Oppo UDP-205's ES9038Pro RCA out although the Oppo ultimately is superior when it comes to insanely low distortion and of course has the option for balanced XLR output.

Here are some graphs:

Left / Right channel balance is excellent across the spectrum. At most +/-0.01dB difference between channels which could just be representative of variation with the interconnects and ADC used.

Very impressive results from this little DAC! In terms of distortion and noise level, the Topping D10 is around the performance of the TEAC UD-501 while the Topping DX3 Pro is approximately at the level of the Oppo UDP-205 RCA out.


For completeness, let's look at the measurements at 192kHz. In reality, I have few albums at this samplerate and honestly don't have any special desire to waste storage space on these (regardless of whether storage is "cheap"). Summary chart with the same devices:

Again, excellent performance from the DX3 Pro. A couple of graphs for frequency response and noise level:

I have measurements up to 24/384 and the results look good. But seriously, who cares? Anyone have albums at 384kHz? :-)

However, let me reiterate something from the 384kHz data. Here's the noise floor of the DX3 Pro alone keeping it nice and clean:

The rise in ultrasonic noise isn't terribly high even into 192kHz and is a reflection of the combination of DAC and ADC's modulator noise. But notice just how clean this is for the stereo RCA output! No noise peaks at all. And this is all using the stock switching power supply. Remember this when you hear about folks online spending money on often very expensive linear power supplies for their DACs, computers, and streaming devices claiming that the power supply somehow has special abilities to keep noise level low! Unless these audiophiles/companies can prove such a thing, it could all be nonsense and in fact, one could be introducing noise into the playback system while wasting money and making the system less power efficient.

Time to try out DSD mode...
Let's have a look at some DSD measurements using PCM-->DSD converted RightMark signals with JRiver 24. DSD playback in AKM DACs might benefit from the "volume bypass" pathway which circumvents the internal delta-signal modulator and data is sent directly to the SCF (switched capacitor filters) blocks [see the block diagram in the spec sheet p. 2].

Remember that DSD playback can have lots of ultrasonic noise due to the use of strong noise shaping to keep noise level low in the audible frequencies (thanks to 1-bit quantization). The Topping DX3 Pro provides the option of 39kHz (default) or 76kHz low-pass filtering. I would recommend staying with the default for typical DSD64/128 playback, the 76kHz setting would be fine for DSD256/512 but I doubt any of us have many of those recordings either!

Anyhow, here are summary results of the 24/96 RightMark test signal converted to DSD64/128 to show resolution and noise level differences. Low-pass filter kept at default of 39kHz:

Looks good. No surprises really, and highly suggestive of "transparent" hi-res PCM to DSD conversion. Remember for the distortion and noise measurements, RightMark is calculating from 20Hz to 20kHz. As such, DSD64 is capable of good "high resolution" within the audible spectrum. It's in the ultrasonic frequencies where we start detecting noise.

Here are the comparison graphs:

Again, this is all rather typical of DSD. DSD64 performs similar to 24/44.1 with the noise rapidly rising after 20kHz. DSD128 is more akin to 24/88.2-level performance (we can start to see a little excess noise at 40+kHz) and if we were to continue that comparison, DSD256 will have similar performance to 24/176.4 which is why if you wanted to use that samplerate, you could increase the DSD low-pass filter setting up to 76kHz.

IV. Stepped Sine Tests

I haven't done this previously with my DAC measurements but it's worth having a look for comparisons. The newer beta versions of Room EQ Wizard (currently 5.20 beta 55) have the ability to use the stepped sine facility to measure harmonic distortion across frequency and output levels. As usual, amazing work from John Mulcahy!

All tests performed at 96kHz with 131k point FFT using the RME ADI-2 Pro FS as my standard set-up. Again, the DAC has been maintained at filter F-1 (linear phase, steep roll-off).

For the Topping DX3 Pro, here's what the frequency stepped sine distortion graph looks like:

Across the frequencies, for the most part, we see a pattern of harmonics where lower order (2nd and 3rd) components generally predominate over the higher ones. In principle, this should be good for nice clean hi-fi sound quality.

We can compare this to the Topping D10 and its ESS Sabre ES9018K2M DAC:

Overall THD of the Topping D10 is higher than the DX3 Pro, mainly because of the higher 2nd and 3rd harmonics. The higher order harmonics are very effectively suppressed at -3dBFS as you can see. Notice that the 3rd harmonic rises above the 2nd above 2kHz and becomes the predominant harmonic in the high frequencies.

In REW, we can also perform an amplitude level stepped sine measurement:

The top half is the FFT of a 950Hz tone at the end of the sweep with the fundamental signal at 0dBFS. I'll speak more about the choice of 950Hz instead of 1kHz below.

The bottom half is the stepped sine measurement as the fundamental 950Hz tone is gradually increased from -120dBFS to 0dBFS measured every 3dB (4 sample average). We can visually inspect the linearity of the amplitude steps; notice that I have overlaid a very fine red line through it. Linearity looks excellent even down to -110dB. Beyond that, we can see slight deviation from the red line as the signal encroaches into the noise floor. At the bottom of the graph, we see a measurement of THD, 2nd and 3rd harmonics. As you can imagine, there are limits to how low we can measure these levels based on the ADC system and noise. We can see that above -15dBFS, there is a rise in the 3rd harmonic which is also reflected in a slightly rising THD above -10dBFS.

Here's the frequency stepped sine data reformatted relative to the 950Hz fundamental:

As you can see, through most of the amplitude range, THD is primarily consisting of the 2nd and 4th harmonics until -13dBFS where the 3rd harmonic arises. Above -7dBFS there's a bit of "saturation" resulting in overall THD rise.

Again, for comparison, here are the same amplitude level stepped sine graphs using the Topping D10:

If we look closely at the thin red line overlaid on the fundamental, we see that it deviates from linear below -100dBFS; not as good as the DX3 Pro as expected, but realistically, good linearity below -90dBFS is more for bonus points rather than "essential" resolution unless one's soundroom is located in an anechoic chamber. :-)

And if we plot the harmonics relative to the fundamental 950Hz sine wave:

Quite a different picture emerges compared to the DX3 Pro with this DAC showing more fluctuations in the relative levels of harmonics depending on amplitude!

While the DX3 Pro and its AKM DAC has a more predictable pattern of 2nd and 4th order harmonics through much of the amplitude range, with the D10's ESS DAC, notice that the harmonics vary quite a bit more relative to each other and the 3rd harmonic became most prominent between -47 to -30dBFS. While I certainly would not claim that such differences are significantly audible, it's interesting to see the different "signatures" the DACs leave. These are some of the subtle differences between ESS and AKM DAC chips we would not notice when looking just at a single THD(+N) number. I know some audiophiles claim to have preferences for or may dislike the sound of certain types/brands of DACs (so-called "Sabre glare" for example which I can't say I've personally had concerns with).

Also, it is known that some ESS-based DACs have the THD/IMD "hump" as discussed here; not really an issue with the D10 as far as I can see other than the elevated 3rd harmonic between -47 and -30dBFS. Maybe a very slight bump from -39 to -17dBFS.

V. Jitter

As you know, I'm not all that worried about jitter significantly affecting sound quality these days unless truly atrocious (as discussed here).  Jitter is essentially a toothless boogeyman used to sell products that are likely unnecessary IMO since decent asynchronous DACs these days have no need for any special additional jitter reduction mechanism.

When it comes to the Topping DX3 Pro, we can see that there is a little bit of data jitter showing up in both the 16-bit and 24-bit tests with the USB interface: 

Note the accentuated proximal sidebands on either side of the fundamental. These side bands correlate with the 229.7Hz square wave embedded in the lowest bit of the 16-bit J-Test.

The low-level jitter-related anomalies are easier to see with the 24-bit test:

This pattern of J-Test would not be audible due to extremely low levels (only around -130dB peak) and the proximity to the fundamental frequency would mask audibility further.

Yes, jitter performance can be improved with this DAC. No, things like UpTone's USB Regen would not improve the situation because the jitter is intrinsic to the clock inside the DX3 Pro itself, not dependent on the computer/streamer - feel free to prove me wrong!

Since USB is not the only wired input, here are the jitter results from the S/PDIF interfaces - coaxial and TosLink. I used my old Squeezebox Touch S/PDIF output which is not known for low jitter as the source:



As you can see, asynchronous USB simply performs better compared to S/PDIF for most devices when it comes to jitter.

Remember that typically, coaxial S/PDIF has higher bandwidth than TosLink which requires conversion of electrical to an optical signal and back. The benefit of TosLink of course is galvanic isolation which may or may not be needed (typically unnecessary). As you can see above, generally, coaxial S/PDIF provides better jitter performance than TosLink which is more evident when you compare the 24-bit results. In any event, with the fundamental signal at -6dBFS, the jitter-affected sidebands are still below -120dBFS. Remember, the S/PDIF source will have an effect, so a more accurate device than the Squeezebox Touch should be cleaner than the FFTs above. Also, some DACs like the Oppo UDP-205 will also achieve intrinsically lower jitter using its S/PDIF inputs.

Pssst... Want to see almost "perfect" J-Test results with the Topping DX3 Pro?

Beautiful. This is the J-Test result when the signal is upconverted to DSD128. DSD64 is basically just as nice looking. I suppose if one is aiming for "perfection", upsampling PCM to DSD128+ with a high quality algorithm (like HQPlayer) likely will get you very "accurate" results. You'll need a powerful playback computer or server (eg. converting through Roon Core) though.

VI. Subjective Listening Impressions & Conclusions

Okay, let's end off with some subjective impressions, listening comments and summary.

It sounds good. As a traditional USB DAC which is how I measured the DX3 Pro here, it's all plug-n-play to the Linux-based Raspberry Pi 3 streamer. The Topping USB driver for Windows with ASIO has been stable on my laptop. The Bluetooth streaming from my smartphone works well also and with a bit of fiddling around on my Huawei P30 Pro with Android 10, I was able to select which Bluetooth codec music was being transmitted through using the Developer Options. I can easily cycle in realtime between SBC, AAC, aptX variants, and LDAC. I was suitably impressed by the sound of LDAC at >900kbps "Best Quality" setting which was the default for my phone with up to 24/96 target quality.

Up to now, most of my listening has been with the headphone output to my Sennheiser HD800. The Sennheiser's high nominal impedance of 300Ω is a great match. Since I measured the RCA out mainly, see WolfX's measurements for headphone out performance (I might do my own measurements at a later time). Fidelity is excellent, consistent with the measurements. A fellow blog reader David S. recommended some Monte Montgomery albums and I recently got his live CD New & Approved (2003, DR7) which is one of David's "desert island" picks. I agree that this is a great album for music and sound (still wish the studio engineers laid off the compression of course :-). Energetic performances, remarkably detailed sound of guitar and percussion! I love the audience participation on "Tug of War", and the cover of Hall & Oates' "Sara Smile" is great. The DX3 Pro provided plenty of power, volume can be pushed up to deafening levels with the Sennheiser. Excellent rendering of the frequency range from deep bass to limits of upper frequencies, nice transients on the percussion and realistic rendering of vocals.

The other album from Montgomery I enjoyed was the studio effort Mirror (1999, DR9). A great showcase of the Austin, TX guitarist. As an aside, I listened to this album with my 1MORE QuadDriver IEMs which are only rated as 32Ω and they still sound good even if not optimal and certainly not "reference" quality like the Sennheiser HD800. The 1MOREs have an accentuated bass response which could work well with some music. One pairing I found to be excellent was the DX3 Pro with my old AKG Q701! Plenty of power to drive these 62Ω 'phones and the resulting sound was very pleasant with adequate bass strength; I have found lesser headphone amps to sound anemic with these.

I have not needed to use the +9dB gain setting as my headphones are all sensitive enough to not need so much power (nor do I listen to music too loud!). Good to know the extra "oomph" is there if needed!

So, bottom line... The Topping DX3 Pro is a great little DAC for not too much money (currently ~US$220). The higher-end AKM DACs are right up there in terms of sound quality if accuracy, high-fidelity and "transparency" is what you're after (no romantic/sentimental tube-DAC sound here, friends!). I really like the convenience of the remote for control of settings and general turning ON/OFF from standby. The OLED display is a nice size with good functional details.

The main "limitation" with this device is the higher headphone output impedance (~10Ω). Othewise, while I would have been happier with lower jitter measurements, it's not audible anyways. It'll be cool if Topping came out with a V3 that addresses the output impedance, cleaned up jitter a little more, maybe go with a 1/4" headphone jack to be even more "pro" - that would be "perfect".

Needless to say, using this as a Bluetooth DAC with its powerful headphone amplifier is practical, flexible, and something I will very much enjoy in regular use in the days ahead streaming from my cell phone, tablet, and laptop!

As usual, great to see technological progress continuing to provide more ways to enjoy music, maintain fantastic sound quality, and at an unapologetically great price point for meaningful "hi-fi end" gear catered to all music lovers!


I mentioned above I would discuss why I chose 950Hz instead of 1kHz for the amplitude stepped sine measurements. It basically has to do with the fact that the 8th harmonic of 1kHz would be right at 8kHz. Remember that we can detect 8kHz PHY microframe packet noise in USB devices. Since I have both the Topping DAC and RME ADI-2 Pro FS connected to an inexpensive USB3.0 hub when making the stepped sine measurements, elevated 8kHz noise will distort the level of the 8th harmonic.

How much 8kHz noise do I pick up from all this interconnected USB activity? About this much...

It's down at -125dBFS even with both the Topping D10 and RME ADI-2 Pro FS connected to the same inexpensive USB 3.0 hub into the Microsoft Surface 3 Pro; no special "filtering" used.

Remember, a few years ago John Swenson claimed to audiophiles that this 8kHz PHY noise is a big deal - "since the rate of packets is 8KHz there are strong components of this noise in the audio band". Hmmm, I would not consider less than -120dB noise exactly "strong" even with a DAC like the D10 that is also USB-powered!

This supposedly "strong" noise was at least part of his justification for the UpTone USB Regen back in 2015. After all these years, I have yet to see the company publish any results to show their device suppressing the 8kHz noise or demonstrate any benefit for jitter. All we have are lots of words and some subjective testimony as typical in the audiophile world.

Without objective evidence, I fail to see why anyone would pay money to hang all kinds of doohickeys off their USB ports whether the Regen, or AudioQuest's JitterBug, or the iFi USB iPurifier variants.


In other news...

A friend texted me when he saw that Apple is going to be introducing "Spatial Audio" updates to the AirPods Pro with the ability to simulate 5.1/7.1/Atmos content. You can see the WWDC 2020 Keynote video here - fast forward to 43:20. It looks like it will incorporate much of what Redscape is capable of for head-tracking wirelessly using the AirPods Pro's internal accelerometer along with DSP to simulate the multichannel "surround" effect.

To synchronize the soundstage with motion of the mobile device and keep the sound "anchored" seems like a neat trick. I look forward to giving this a try at some point although I have some suspicions about the accuracy of the head and device tracking - hopefully it's "good enough" as a first implementation. Also, remember that the AirPods Pro's H1 chip can only handle the AAC codec and I suspect have limited DSP power otherwise. Therefore, I assume the vast majority of the surround processing is being done by the mobile device. This could be a lot of work for the iPhone or iPad handling the HRTF processing, encoding in AAC for Bluetooth transmission and achieving minimal latency in the process if you're watching a movie for example. Hearing is believing and I hope to be impressed by Apple knowing their usual slick "magical" hype in the promo presentations.

As I said a year ago (see Multichannel and the Audiophile), getting the "masses of headphone users interested (in multichannel) with HRTF-based DSP-reconstructed binaural playback" would be very useful to getting us more surround content ahead.

I see that Tidal is already streaming Atmos-encoded content (currently something like 40 albums). Now this I can support, not that nonsense called MQA even though it's a lossy Dolby Digital+ stream. It would be very interesting if this Apple AirPods Pro update is compatible and significantly improves the experience of streaming this type of content.

Recently, I listened to one of the first Atmos-encoded music Blu-rays - INXS' Kick 30th Anniversary (released 2017).  I love this album having enjoyed it when it came out in my high school days but I must admit the results were mixed. Love the bass-heavy spatially-expanded "Guns In The Sky" at the start. Also enjoyed the "Never Tear Us Apart" mix. "Need You Tonight" seemed a bit too rear-channel accentuated for my taste as if most of the music were coming from behind. And "Mystify" just sounded too harsh and dated. Regardless, I'm a big surround music fan so I'd love to have more multichannel albums coming, Atmos or otherwise.

Have a great summer everyone! I'll be on vacation for a good part of July. Free time permitting, I might post some "Summer Musings" as I try to catch some R&R on a family road trip...

Stay safe especially to the American friends. I'm really quite proud of how British Columbia maintained communications and managed the pandemic with great results to show from the measured, calm, science-based, more objective, unifying, rational approach thus far.

Hope you're enjoy the music!


  1. Great stuff again Archimago. This type of information is very helpful for music lovers like me who have limited funds to devote to audio equipment. It helps me to recognize that I don't have to spend ridiculous sums of money for excellent performance; something that would not be evident if I were completely dependent upon the typical audiophile press reviews of high price equipment. I am curious of one additional feature on the DAC and that is the volume control. I have read so much conflicting information on where in the signal chain is the best for volume control, as well as the hardware involved. I'm an electrical engineer and much of the discourse sounds like complete audiophile nonsense to me. Have you ever measured and compared different volume control methods and hardware? I ask because I am considering using a DAC like this one to feed directly into a DIY AMP similar to the HYPEX based amplifier that you built.

    1. Thanks for the note...

      Absolutely, there is IMO no need to spend ridiculous amounts of money on "high end" audio gear. This is of course why I used the phrase "hi-fi end" gear in the discussion above. The truth is that if we want to listen to products which can be verifiably of excellent fidelity, accurate to the source content (ie. your 16/44 CD rip, 24/96 download, etc...), then a DAC like this for <US$300 will already get you there without dramatic fanfare.

      As I've said in the past, I certainly have no qualms about people spending thousands and tens of thousands of dollars on gear. We're all entitled to satisfy our cravings around fashion/style/pride of ownership/"non-utilitarian benefits". We just need to be careful about unrealistic claims with no rationale or claims not based in facts.

      Yes, you can use something simple like this with the Hypex amp! Just make sure you don't accidentally set the RCA out into "line out mode" rather than "preamp mode" and blow out the amp/speakers playing some nasty compressed music at full volume :-).

      As for quality of volume control, no I have not measured the digital volume control, but as you can imagine, I have no reason to be concerned. The AK4493 is a 32-bit part and this will provide plenty of room for attenuation of both 16-bit and 24-bit data without loss of resolution, only limited by the (very low) noise level...

      All the best!

    2. My understanding of analog vs. digital volume control is

      Analog volume control: noise floor goes down as volume down, but there can be issues with channel balance at lower volumes, particular with pots.

      Digital volume control: noise floor stays constant, but they usually immune to channel balance issues

      However, since the noise of the Topping and similar DACs is well below that of most amps, speakers, and rooms, the constant noise floor of digital volume controls is a non-issue IMO.

    3. Thanks for the reply Archimago. I don't have any problem with people spending their money the way they want to either. It's just the audiophile publications and the disservice they are doing describing how "liquid midrange", "tight, punchy base" and "micro-dynamic detail" are all hugely present in the expensive DACs to the point that "veils are lifted" when compared to more pedestrian fare; gets tiresome.
      And volume control is another area where I see people on forums simply parroting what they read in some of these publications. I was just wondering if, with my background, I was being dismissive of something I haven't put a lot of research into. We have indeed come a long way since my college days working with a Motorola MC6809, 8 bit processor, and coding in machine language.


    4. AK4493 support velvet sound. The description on the AKM website indicates that internal processing occurs in 36 bits. There is no any problem with digital volume control
      "VELVET SOUND's 32-bit product line is equipped with a high-resolution digital core that has ben extended to 36-bits, enabling the re-creation of even the faintest sounds and a truly realistic high-resolution experience."

    5. Hi Dave: Yes, generally you correct, the noise floor with good analogue volume controls will go down while digital volume control will attenuate the top while noise level stays constant. As you noted, the noise floor of this DAC is already excellent so it's not an issue. Just have to be careful if we add an analogue volume control in the chain potentially also adding distortion and noise.

      Hey Joe: Yup. It's one thing to subjectively express opinions and another when we see magazine writers taking all kinds of liberties and IMO exaggerating what they are able to hear, expressed in language that may be misperceived. Cool man - 6800-series Motorolas! I had fun with the 680X0 series back in the day :-).

      Thanks Michael for the info on "Velvet Sound". 36-bit eh? Even better!

  2. Apologies for pestering you @Archimago as I posted this on old D10 thread too, but.. Any chance you could help me with the correct settings for Topping D10 on Picoreplayer. I have been having trouble with it power cycling on off at various times including when sample rate changed.

    1. Hi shoddy, sorry didn't see previous message... I'm sure lots of comments in previous posts missed!

      It's been awhile since I had that PiCorePlayer + D10 combo. Lemme try to set this up again with my other Pi and see if I run into power cycling issues. I presume your Pi is acting like a streamer end point and always turned on? No funky tweaks like the CRAAP settings which is undervolting? :-)

    2. Thanks that would be very kind of you. The Pi is just running as a pseudo squeezebox with lms on a different pi. No fancy tweaks. Weirdly I had a problem with minor pops using max2play, so thought I'd try pcp. Pcp does not have the pops, but goes into the weird power cycle when I change rate. I tried a fresh max2play on another card and now that won;t work at all and is now doing the power cycle too. I thought linux was sposed to play nicely with usb dacs.

    3. Hey shoddy,
      Yeah, typically Linux plays nice.

      Are you seeing Pcp going down during this rate change? Or is it the D10 running into power down?

    4. One more thing, how's the quality of your power supply?

      Since the D10 runs off the USB port, make sure you *at least* have a 3A supply especially if you have the Pi 3 B+ and maybe 3.5A for the Pi 4.

    5. Hey shoddy,
      Just quickly set-up and currently running a Pi 3 B, older piCorePlayer 4.1.0 connected to the Topping D10. All running off USB battery pack. Ethernet to my LMS on the home server.

      Playing a compilation album of music ranging from 16/44 to 24/192 with a couple of 24/88 tracks. Playing about 45 minutes now. No power issues. D10 switching samplerate as expected (and sounds great on my desktop speakers).

      Standard Squeezelite settings on piCorePlayer: "USB audio" output device, rebooted, "front:CARD=D10,DEV=0" for output setting. Everything else default.

      Good luck! Will let you know if I run into any issues as I just let it play for a couple hours or so here...

    6. Thanks again @Archimago . It seems I am an idiot and was using a 5v 0.75A supply. I have replaced with 5v 2A and all seems to be well. That said I have a nagging feeling I can hear the very low pop, but I think I'll have a lie down. Sorry for wasting your time.

    7. No worries shoddy! A pleasure to help where I can...

      Gave me an opportunity to have a look at piCorePlayer again and update to 6.1.0 which worked fine on my Pi 3 B. I had a feeling it was power-related rather than the software side...

      Again, given the Topping D10 is 100% dependent on the pi's USB power, I would give the system 2.5-3A (especially if you have B+/touchscreen/USB sticks hooked up).

  3. I wrote to Topping and suggested that they include the balance adjustment in the remote control. They refused saying that "it will confuse the user".

    It's a pity. Because I got used to being able to adjust the balance without leaving my sweet spot (I have Wyred4Sound DAC-2). I absolutely hate when the music sounds not centered, it ruins my pleasure.

    1. Interesting idea fgk and indeed important fine-tuning option that would be nice to see in more devices!

      Yeah, don't know about the answer about "confusing the user". I wonder what's the average IQ of their customers? :-)

      But seriously, if the customers aren't confused by what FIR filters are, what are the chances they'd be confused about balance settings?!

  4. I would just add that I bought a Project S2 (DAC only for $299) and really love this little dac and the 5 filter choices it offers. Punches well about its price point and no quality issues so far. I was concerned about the analogue output stage being powered my only 5VDC, but not an issue to my ears. It definitely improved the sound of my 2003 Sony SACD player for pcm playback, and it can playback my homemade 2496 dvd discs with great results.

    You are right that highend can be affordable. Off to buy some Schitt shortly and give them a try. Phone stage first I think.

    1. Great job Jim,
      I had a listen to the Project Pre Box S2 last year and I agree. For the price, it's a great deal on an ES9038 DAC!

      These days, given progress not only in quality of the components with higher resolution, better time-domain performance, etc... also comes much improved power efficiency. I have zero concerns about DACs powered with little 5V switching power supplies these days and don't understand all the hand-waving about linear supplies for example and why people would want to spend hundreds (even thousands?) of dollars!

      Have yet to see evidence that the aftermarket "audiophile" power supplies have any beneficial effect despite all kinds of testimony by the usual suspects :-).

    2. so I took my Project S2 dac up to my bedroom listing station that consists of a denon 290 carousel player and a Prosonus hedphone station. The bass of the Denon as always been floppy, uncontrolled, but with my sennheiser HD 280s it was fine when I could not sleep. I could not use my better Audio technica ATH 50X's as they have a bloat at 200Hz that is a very bad match for this Denon player.

      That all went away when I use the Project S2 dac with this $100+ 5 disc transport. Now every thing was in better focus and I could use the AT 50X's and loved the greatly improved sound.

      If you are a 5 disc carousel owner this S2 dac is what you need to really help it out. If it is a headphone station for you, the get the $399 S2 with the built in headphone amp.

  5. I agree. Makes no sense for me to spend $200 on a power supply for a $299 DAC. If I do that I should have looked at a near $600 DAC from the start.

    1. Yeah Jim,
      But even with a $600 DAC, one better make sure the $200 power supply actually improves things! Sometimes on a wise spectrum FFT we can see little noise issues that may not be very evident with listening or ultrasonic anomalies that one just doesn't want to be present in the system...

    2. Agreed. I would have to wonder how many $600 DACs would be better than the Topping or This Project S2? I am amazed at how far digital has come. I still have my first MidiMan Flying Cow playback computer card and the external Flying Cow ADC that went with it for getting digital into my computer. It is here sitting on the shelf. I used the external unit with my Sony DAT for recording 44.1 files as the DAT only did 48khz do to SCM. My DAT still works great and I still use it on occasion. I had sold the MimiMan super DAC I wish I had kept.

    3. Wow. The Flying Cow ADC/DAC... A blast from the past - around 2000 with 48kHz being max samplerate, right?

      I had thought about getting one of those ADCs around 2005 for measurements but because of that 48kHz limit waited a few more years until the Creative E-MU 0404USB became readily available (with 96/192kHz which I used for some of the earliest measurement posts). It's one thing of course to use ADCs for measurements... Another altogether for recording actual music and I'm certainly happy with 48kHz for that!

    4. Some of us tried to be early adoptors with slow computer speeds. I really liked the first Adobe audio program, Cool Edit, as it worked great and was very intuitive. THAT is a blast from the past. Amazing all the things we can do now. I am guessing that a vinyl lathe had been affordable we would have been cutting our own lacquers.

  6. I've got the Air Pods Pro, love 'em. Best ANC out of everything I've tried.

    I believe the processing will be very low latency because of my experience with the Audeze Mobius and Waves bluetooth headtracker. It needs to be low latency to be believable. The chips on the iPhones will handle the computing power with no issue - considering whatever Mobius is doing works in DSP and Apple is far ahead in the silicon game.

    Very excited about this myself. Although I love Impulcifer it's going to be neat to be able to pair multiple Air Pods Pro's to my Apple TV and watch together with head tracking.

  7. Forgot to mention - I've tried TIDAL Atmos content on my real 7.1.4 system. Quite neat - I like it, but not enough to pay for it really. It suits genres like Hip Hop really well, but for the type of music I like it's not really suited that well.

    What was neat was that TIDAL was sending correct offset values in Atmos - so you get a proper reference level for music finally. It means any dynamic EQ settings your AVR has now works well with music. People will no doubt complain that the level is low though - loudness wars and all that.

  8. My Dx3 Pro Ldac worked fine until the USB input stopped working this morning. The display still shows "96" but windows 10 is not detecting it anymore. Tried 2 different PCs and 3 different USB cables, reinstalled the driver, etc, no dice.

    1. Yikes Shaken,
      Hope it's still under warranty and you can get a replacement.

      Mine still working well as I've started using it more in my main computer workstation now to replace my older ASUS Essence One DAC.

    2. I fixed it. It wasn't a hardware issue, but a driver firmware issue. When you update the firmware you need to remove the power cord and restart the DAC itself rather than just restart your computer. It's a good unit but Topping needs to work on the instructions. It would also be nice if they put a password function into the BT input.

  9. Hi Archimago, I have the hd600 and I am interested in this dac/amp but I read the headphone out has high impedance. How does it impact the hd600? Why is it a problem? I read that you plugged your hd800 in the rca out. The hd800 has the same impedance as the hd600 so if I use a jack to rca cable and plug my hd600 in the rca like you did, it should work well?

    Thank you for this test and your answers

    1. Hi Furu,
      For impedance, have a look at this for discussion on why it matters:

      Sennheiser HD600 headphones are rated at 300-ohms and pretty sensitive at 97dB/mW. The impedance with these headphone outs at 10-ohms isn't a problem if you use the 1/8th rule-of-thumb as per the article above.

  10. Hi
    Can you please tell me the difference between dx3 ldac and dx7 and d90?
    I have ordered a dx3 to use on my headphones. But in my hifi system I'm looking for a new dac, and I wonder if the dx3 will do a ok job, or if the dx7 or d90 is a better idea. I'm not using balance system.
    Great review 👍

    1. Hi Unknown,
      DX7 - based on ES9038Pro DAC, has balanced outputs for both headphones and speaker system.
      D90 - top of the line AK4499 DAC. Balanced out and essentially state of the art modern DAC fidelity. No headphone out though.

      The DX3 will be fine IMO, but if you're itching for even higher resolution then look at those others!

    2. Hello, Archimago, sorry for asking, im using right now Philips fidelio x2hr, thinking about some beyerdynamics in the future, and i guess beyer with 250ohm is ok for dx3 v2 with headphone output impedance <10Ω. but what about my current headset x2hr with 32ohm, can i use it together?

    3. Hi Plung,
      Yeah, no worries, you can certainly use the Fidelio X2HR even if the impedance matching is not ideal. Compared to a lower output impedance amp, you might not be able to drive the headphone as loud (current limited), there might be some frequency response changes (depends on your headphone's impedance curve vs. the amp), and bass might not be as well controlled (less overall damping factor).

      I've tried lower impedance headphones like my 1MORE IEM and it still sounds very good at my preferred listening levels even if not ideal.

  11. Ho from Italia! It Is ok for my Philips Fidelio X2/HR? Thank you and excuse me for my bad english..:)