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Review and Measurements of Topping DX7s DAC and Headphone Amp

amirm

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#1
This is a very much anticipated review of the Topping DX7s which is a replacement for Topping DX7. As you see in this picture of them in my lab, they are twin brothers as far as enclosure, and features:



Even the remote from DX7 works to operate the DX7s. Alas, the price is higher for DX7s retailing for a list price of $499 which is $100 higher than DX7. Recently it was offered on Massdrop however for something like $375.

NOTE: The Topping DX7s was offered to me for free from Topping when I asked to purchase it. For that, I am appreciative. I have not offered anything in return to Topping, nor do I have any kind of commercial relationship with them. They also sent me the Topping D50 which I will review separately. Feel free to read as much or as little bias as you like into this review.

The DX7s upgrades the DAC (chips) to a pair of ESS ES9038s. Due to higher cost of this chip vs the ES9018 used in DX7, that is reflected in the higher retail price of DX7s. Unfortunately the amazingly high quality remote of DX7 has also been optional (see other using low cost universal remotes: https://audiosciencereview.com/forum/index.php?threads/wtb-remote-for-topping-dx7.2334/

As I mentioned in the review of Topping DX7, this is one superbly built unit. It feels exceptionally solid and hefty with very nice industrial design. Other than its half-rack size, it would easily fit the bill as a "high-end" DAC. Its weight easily supports heavy cables and doesn't let them drag it back.

The unit was plug-and play in Windows 10, requiring no drivers for bit-exact playback using my favorite player, Roon.

Format support is excellent extending to DSD as is connectivity which even includes professional AES/EBU balanced digital audio input.

On the front-panel there are standard and "balanced" headphone outputs. I will evaluate that section in a later post. For now, this post is focused on the unit as a stand-alone DAC.

OK, I know almost all of you want to know how it measures against Topping DX7. So let's get into that.

As always if you have a question about my measurements, please read about the setup and what they mean here: https://www.audiosciencereview.com/forum/index.php?threads/understanding-audio-measurements.2351/. And if you want to know if I am qualified to make such evaluations, see my background here: https://www.audiosciencereview.com/forum/index.php?threads/a-bit-about-your-host.1906/

The unit was tested after being on for just a few minutes and has less than 1 hour of use on it.

Measurements
Starting simple with frequency response measurement using default Brickwall Filter we see:

Topping DX7s DAC Frequency Response Measurements.png


There is a tiny amount of imbalance between the two channels. Usually these two lines land on top of each other. Here they are off by .04 dB.

Next let's look at jitter and noise measurements using 24-bit/48 kHz jitter test tone over S/PDIF:

Topping DX7s DAC Jitter Measurements.png


Performance is excellent and identical for both DACs. I just remembered that I forgot to run this with USB. Will do and report back on that.

Let's now look at our favorite, the linearity test:

Topping DX7s DAC Linearity Measurements.png


I followed my rule of 0.1 dB deviation as the cutoff point. As luck would have it for Topping DX7s, it got to that point hair before DX7 indicating that 18 bits vs 19. But if I run this repeatedly it would change a bit at that extreme which is at the edge of what I can measure. Both DACs are showing exemplary performance here with essentially flat line to 120 dB indicating 20 bits of resolution. No other DAC I have measured has done so well.

Looking at the waveform of a very low-level sine wave at some -90 dB, we see this:

Topping DX7s DAC Linearity -90 dB Measurements.png


Unfortunately I didn't realize the scales were a bit different but to my eyes, the DX7s seems just a hair cleaner. Either way, both show a very nice approximation of a sine wave.

Next let's look at THD+N noise and distortion figure at different frequencies:

Topping DX7s DAC THD+N Measurements.png


We have a bit of a mixed picture with Topping DX7s doing better from 2 kHz to nearly 20 kHz but somewhat worse between 200 and 2 kHz. The levels regardless are very low at less than -102 dB. All in all if I had to pick a winner here, I would pick DX7s since our hearing is most sensitive in 2 kHz to 5 kHz.

Let's see how they both do at SMPTE intermodulation test:

Topping DX7s DAC Intermodulation Distortion Measurements.png


A somewhat mixed picture appears here again. The DX7 seems to be dominated by noise whereas the DX7s has some odd behaviors. I wonder if this is due to distortion compensation logic in ES9038. Unfortunately unlike the Pro-Ject Pre S2 Digital, there is no option to turn this feature on and off. Overall I would give a slight nod to DX7 over DX7s.

Finally let's look at the residual noise and distortion when we feed them a 1 kHz tone and then filter it out:

Topping DX7s DAC 1 kHz Distortion Measurements.png


This is another mixed picture with some distortions lower and some higher. The DX7s however, maintains a tiny lead in lower noise floor (in red).

Conclusions
Going into this test, I was hoping there would be somewhat significant improvement in measurements with DX7s. That did not come to pass. Performance is excellent as it was with DX7. Perhaps we are limited by the measurement equipment or we are not testing for everything. Given the higher cost of DX7s, I am wishing the DX7 was still available and that would have been my recommendation.

Be that as it may, the Topping DX7s gets my recommendation for a mid-price, high performance DAC. Cut back on a few steak dinners and you too can afford to buy it relative to cheaper offerings! :)

-----

As always, questions, comments, recommendations, etc. are welcome.

If you like this review, please consider donating funds for these types of hardware purchases using Patreon (https://www.patreon.com/audiosciencereview), or upgrading your membership here though Paypal (https://audiosciencereview.com/foru...eview-and-measurements.2164/page-3#post-59054).
 

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Jinjuku

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#2
Thanks Amir and that is a sleek looking piece of gear.
 

pos

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#3
Thanks Amir!
We have a bit of a mixed picture with Topping DX7s doing better from 2 kHz to nearly 20 kHz but somewhat worse between 200 and 2 kHz. The levels regardless are very low at less than -102 dB. All in all if I had to pick a winner here, I would pick DX7s since our hearing is most sensitive in 2 kHz to 5 kHz.
Are the frequency values in that graph related to the source generating the distortion products, or to the distortion products themselves?
Not sure that makes sense (language barrier, sorry), but for example would the 2nd order distortion generated by a 1kHz signal be represented at 1kHz or 2kHz in that graph?
 

amirm

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#4
Are the frequency values in that graph related to the source generating the distortion products, or to the distortion products themselves?
The former. The analyzer sweeps the frequency and measures (using a dedicated THD+N meter), the distortions created.

If you want to see the latter, the 1 Khz residual noise and distortion is that.
 

pos

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#5
Ok thank you. That makes the THD curve of the original DX7 a little more appealing in my opinion.
It is so low that is probably does not matter anyway.

I am a little bit disappointed by this s version I must say.
I needed the lower noise floor so the original version would not have filled the bill, but that imbalance problem and frequency response shape looks weird to me, especially with these new chips that are supposed to have some sort of compensation mechanisms that the older ones did not have. At least that is said to be the case for the ES9028pro/ES9038pro compared to the ES9018. Probably different animals in the end...
Anyway these imbalances and response anomalies are easy to compensate with DSP, and measuring each unit is probably a must here (the specs talk about a 0.3dB imbalance, so this might be a maximum that some units might reach), but this is strange and annoying.

Does the frequency response in the pass band look the same with other antialiasing filters?
 

Jimster480

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#6
Interesting to see how this stacks up vs the D50 or the D10 now.

So far the DX7S isn't an improvement over the DX7 so I guess I have no reason to replace my DX7 and I can just continue to enjoy it every day :)
 
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#9
Maybe the major changes have been made to the amp. Otherwise this new model makes no sense from a technical viewpoint.
 

amirm

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#10
Looking at the note they sent me they say: "DX7s use better DAC, better USB interface and better headphone amp than DX7. "

I will look at both USB and headphone amp to see if there are larger differentials there.

From functionality point of view, they support double the sampling rate.
 

stunta

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#11
"DX7s use better DAC, better USB interface and better headphone amp than DX7. "

I will look at both USB and headphone amp to see if there are larger differentials there.
Thanks. It would be great to see their claims in/validated. The new DAC chip may be "better", but it looks like Topping did not take full advantage of it? Are you planning a teardown as well?

Its so easy for confirmation bias to kick in with listening tests when newer models are marketed as improvements. This makes it very interesting to measure and compare newer models to older ones from the same manufacturer. Thank you for doing this - this makes ASR even more valuable and probably unique.

From what we see so far, I am a bit disappointed with what Topping has done. With a higher retail price and lack of remote, its overall a downgrade from the DX7 and they have discontinued that model. At full retail price, I am not comfortable calling it a "budget" DAC, but its all relative I guess.
 

pos

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#12
Maybe topping could offer a firmware update with:
  1. an option to turn the THD optimization on/off
  2. an option to manually "calibrate" the imblance between the two ES9038q2m (should be easy enough to do as the device already include a volume control functionality)
 

Jimster480

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#14
Maybe the major changes have been made to the amp. Otherwise this new model makes no sense from a technical viewpoint.
It has the new XMOS vs the older XMOS.

Yes, I plan to do a teardown. Wish ESS had open specs for these parts so that we could see if they improved fidelity or not.
I can get you the specs as I have found them somewhere online. They are better than the 9018 but its not a world of difference. These do use less power though IIRC
 

Jimster480

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#16
Do they drop the amp output impedance to <= 1 ohm ish? If so, it's worth the extra $100 just to be able to use all your headphones through the same box
Nope or I would have ordered one.
I don't see any real change done to the headphone amplifier because the specs are very similar.
 

Jimster480

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#18
Thanks. It would be great to see their claims in/validated. The new DAC chip may be "better", but it looks like Topping did not take full advantage of it? Are you planning a teardown as well?

Its so easy for confirmation bias to kick in with listening tests when newer models are marketed as improvements. This makes it very interesting to measure and compare newer models to older ones from the same manufacturer. Thank you for doing this - this makes ASR even more valuable and probably unique.

From what we see so far, I am a bit disappointed with what Topping has done. With a higher retail price and lack of remote, its overall a downgrade from the DX7 and they have discontinued that model. At full retail price, I am not comfortable calling it a "budget" DAC, but its all relative I guess.
Yes but with the performance of the DAC alone there hasn't been any device tested which is cheaper that achieves the same performance.
The one tested yesterday was around the same price but it has other limitations and no balanced output or amp whatsoever for the same retail cost.

Well that sucks...same here; can't understand why they didn't fix that!
They told me they will work on it for the next version. But the overall reception was good even with this output impedance.... but I responded back to them in email that they are limiting their customer base because most newer headphones are using low impedances causing people to not be able to use the DX7/S amp with these headphones if they wish to use them to their full potential.
 

Jimster480

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#20
Yep...hope they do; it's a showstopper on an otherwise excellent product
If you have high impedance headphones then you have no issues. For me personally I fixed the issue with an o2. But for those who want to use balanced there is no balanced "cheap" amp and unless you have a high impedance balanced headphone you are really SOL.

So partially you are right in that it does take away from the value, I can only hope for a DX7S2 or DX8 with total 0 ohm output impedance.
 
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