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Review and Measurements of Chord Hugo 2 DAC and Headphone Amplifier

amirm

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#1
This is a detailed measurement and review of the Chord Hugo 2 DAC. It retails for $2,700 in US. The unit I had in for measurements was from an ex-Microsoft colleague and recent forum member. I only had an hour or so with it and it is now returned.

upload_2018-2-12_23-27-33.png

This is an odd looking box to be sure. As you see above the oddity continues in its ports with S/PDIF input being a stereo 3.5 mm jack (it has dual S/PDIF inputs as a result). I had my friend operate the unit as I did not even want to try to decode the button lights. The unit has batteries and that is how I tested it, likely giving it an edge in mains related noise/distortion.

The claim to fame of Chord DACs is a super high-tap FIR filter for reconstruction. This one claims over 49,000 taps. This means each (upsampled) audio sample goes through this many computations before a value spits out. FPGAs are custom ICs that are very well suited for this type of application which is what this DAC uses. The tap number has been positioned as a figure of excellence with each newer model sporting more and more taps. Marketing people rejoice! :)

Rob Watts the designer says that there are audible improvements with increased taps. Unfortunately when I asked him whether he had evaluated such merit in blind testing, he said no.

On the software front this DAC unfortunately gets a failing grade by requiring a custom driver or it does nothing. No USB class is supported and plugging in the device without drivers did absolutely nothing in Windows 10. This is a bummer because if the OS driver interface changes and this company is no longer in business, you have a $2,700 door stop.

For my testing I installed ASIO drivers and used bit-exact output to drive it from the PC. Other tests use S/PDIF digital output from my Audio Precision analyzer.

Measurements
For this test I had to pull out the only DAC I have on my bench that rivals it in price, namely the Exasound E32 ($3,400). For a test or two I also threw in the much cheaper Topping DX7 at $400 although I purchased mine for $300.

First, let's run our usual J-Test for jitter and noise. A test tone of 12 Khz should be the only thing visible here with the rest being noise and distortion. I ran the test two ways: using USB output from the PC and S/PDIF generated by Audio Precision Analyzer. Comparison is made to Exasound E32 over S/PDIF:

Chord Hugo 2 DAC -Jitter Measurement.png


We see a very competent execution here with USb and S/PDIF matching each other. The Exasound is just as good but mains related hum and noise is there at very low level which can be remedied with a better power supply. Even as is, that noise is at very low level so not an audible concern either way. So little to complain about in either device. BTW "better" in the graph means better than Exasound E32.

Next let's get another boring graph out of the way, namely frequency response with different filters:

Chord Hugo 2 DAC Frequency Response Measurement.png


The default filter in red has the best frequency domain response with nearly perfect response. The others have small amount of roll off (about 1 dB at 20 Khz). I let subjectivists play with those filters and report back. :)

Let's get into my favorite test, linearity. And ideal DAC would have a flat line meaning it outputs what it is told to output:

Chord Hugo 2 vs Exasound E32 linearity Measurement.png


Both DACs eek out about 18 bits of output before deviation exceeds 0.1 dB (my personal limit). In the case of Exasound it seems to just get noisier. On Chord Hugo 2 it gets funky jumping up and down. Both of them are very respectable though.

Both of them unfortunately get schooled by the Topping DX7 which costs a fraction of them:

upload_2018-2-12_23-55-29.png


OK, let's not spoil our dinner and continue. :)

Let's look at how a very low level sine wave at -90 db looks like in these two DACs:

Chord Hugo 2 DAC -90 db Linearity Measurement.png


Please excuse the dim output for Exasound. It was at a different size window and I had to resize it to match. Regardless, hopefully you see that the Exasound E32 is a closer match to a sine wave and freer of noise/glitches. Its DC offset changes a bit but that is due to power supply hum. Overall Exasound E32 wins.

Let's look at Harmonic Distortion+Noise:

Chord Hugo 2 DAC Harmonic Distortion Measurement.png


Here, the Chord Hugo 2 DAC has higher noise floor but better control of distortion products. I give it the nod since noise is more benign than distortion products.

Next let's look at SMPTE intermodulation test:

Chord Hugo 2 DAC -Intermodulation distortion Measurement.png


The Exasound in green is the clear winner here and by good bit. The Chord Hugo 2 matches the Topping DX7.

Let's compare the distortion and noise products with a 1 Khz signal that itself has been filtered out:

Chord Hugo 2 DAC noise and distortion measurement.png


Chord Hugo 2 pulls way ahead here. Yes it has higher noise floor but otherwise has less distortion spikes. The Exasound produces lot of glitches in 2 to 3 Khz which I suspect is due to mains distortion products.

None of this is audible concern though due to very low levels. Highest peak is at -120 dbFS.

Let's skin this cat differently and look at THD+N vs frequency:

Chord Hugo 2 DAC THD+N Measurement.png


Here the Chord Hugo 2 is the winner (in red). It has similar distortion+noise to Exasound E32 at low frequencies. At frequencies above 2 Khz the noise+distortion jumps up in Exasound. The Topping DX7 and Hugo 2 do the same but at much lower amplitude.

Headphone Measurements
I measured the output impedance of Hugo 2 and compared it to others on record:

Chord Hugo 2 headphone output impedance Measurement.png


At 1.7 ohms, it is very low making it suitable to driving any headphone without changing its frequency response. I need to measure and add the Exasound to this graph.

EDIT: there have been complains about this measurement saying that Chord advertises a much lower number (0.02 ohm?). The only way my measurement is off is if the unit clips under load of 33 ohm. If it does, then that obviously shows a larger drop resulting in impedance to be higher than if it were not clipping. I will try to get my hands on the loaned unit again in the future to confirm this.

Next I am going to show a new test which is the THD+N not against a dummy resistive load, but real headphones. This is based on work done by Benchmark where they demonstrate this problem with rising low level distortion when real loads are used instead of artificial:

Chord Hugo 2 headphone output THD+N Measurement.png


Sadly we see that noise and distortion rise especially in low frequencies. Worst performance is with the Focal Utopia. Best was with Hifiman HE1000 V2. I will need to run this test on my other headphone amplifiers and see how they behave.

Summary
The Chord Hugo 2 is competently designed with measurements that show no obvious design/execution problems. Its high number of filter taps though provide it with no advantage against traditional implementations such as in Exasound E32 or even Topping DX7.

Despite these good measurements, I cannot recommend it due to requirement for proprietary driver. If that is not a concern for you, then I don't see any grave reason to not buy it other than high cost.

As always comments, corrections, feedback, bad jokes, etc. are welcome.

Edit: Speaking of corrections, my friend who loaned the Chord Hugo 2 to me tried it on a Windows machine and it worked with in-box class drivers. So something went wrong on my machine but support is there. So I take my reservation away regarding driver support.

If you like this review, please consider donating funds for these types of hardware purchase 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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#3
I've always wanted a $2,700 door stop!

Thanks for the review.
 
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Sylafari

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#4
What do you exactly mean by the custom driver? Because the Schiit Bifrost and the RME ADI-2 DAC also require drivers to be used on Windows.
 

LarsS

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#6
What do you exactly mean by the custom driver? Because the Schiit Bifrost and the RME ADI-2 DAC also require drivers to be used on Windows.
At the time of Schiit & RME product releases Microsoft didn't have any UAC 2 drivers, now they do.
 

Blumlein 88

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#7
Thanks for this review.

Can anyone comment upon what the designer is thinking when he says the large filter taps control noise modulation at -200 db and that is audible? Because that doesn't make sense to me.
 

Blumlein 88

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#8
Also a view of the white noise for 48 khz recorded at 192 khz might have been interesting with the large filter taps.
 

Purité Audio

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#9
Thanks Amir excellent, if multiple taps did bring an improvement where would that improvement be expressed in terms of measurement?
Keith
 

drconopoima

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#10
Headphone Measurements
I measured the output impedance of Hugo 2 and compared it to others on record:

View attachment 10601

At 1.7 ohms, it is very low making it suitable to driving any headphone without changing its frequency response. I need to measure and add the Exasound to this graph.
Thanks Amir. I read in the Micca Origen + that you took advantage of the Amazon return timeframe and you don't have it anymore, right? Did you measure output impedance in the unit?
 
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#11
Hugo 2 is positioned as mobile DAC/headphone amp. On the Chord website you see it connected to mobile phone. You can put it your pocket, together with iPhone and enjoy your music. This is something that for example Exasound E32 cannot do. In my opinion if mobile device like this can be measured against professional DAC like flagship E32 then it means its engineering is superb. Price? Well, we cannot question the price tag as this is business decision of Chord. I would not buy at this price because I cannot afford that much and for mobile usage I do not believe we need such a quality. But if I had unlimited budget? Yes, sure. It is nice, well built, unique. It is objectively great mobile DAC and headphones amp.
I am only surprised with the Windows OS drivers, that it cannot use native USB Audio Class 2. Especially that for Mac OS and Linux it is driver less. I wonder if this can be fixed with new firmware? With built in Windows driver you loose DSD but the rest should be fully supported. However, this unit has 3 years guarantee, Chord is company with proven history, so they will probably update the driver if needed. However probably sooner the batteries will go dead then the existing driver will stop working on Windows 10 with Semi-Annual Update Channel. But again probably Windows desktop is not the most common scenario how this device is used.
 
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#12
Speaking of which.... would love to see you test the RME ADI-2 DAC....
 

DonH56

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#13
490,000 taps is a lot of latency... What is the upsampled rate? 490,000 samples / 192,000 samples/sec is 2.55 seconds... But I assume the FIR is at the oversampled clock frequency so in reality latency is a small fraction of that, but still likely pretty long.
 

noobie1

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#14
It would suck if Chord went out of business but good SPDIF transports are quite cheap these days. I picked up a Allo Digione SPDIF transport for less than $150 with RPI 2 and case. Sounds as good (if not better) as connecting the DAC directly to the computer.
 

mindbomb

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#15
Thanks for this review.

Can anyone comment upon what the designer is thinking when he says the large filter taps control noise modulation at -200 db and that is audible? Because that doesn't make sense to me.
I think it is just that it has higher oversampling than many dacs, so it should have better noise performance.
 

amirm

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#16
490,000 taps is a lot of latency... What is the upsampled rate? 490,000 samples / 192,000 samples/sec is 2.55 seconds... But I assume the FIR is at the oversampled clock frequency so in reality latency is a small fraction of that, but still likely pretty long.
Correct. Stated latency was half a second by Rob Watts for the 100k version.
 
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rebbiputzmaker

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#17
It would suck if Chord went out of business but good SPDIF transports are quite cheap these days. I picked up a Allo Digione SPDIF transport for less than $150 with RPI 2 and case. Sounds as good (if not better) as connecting the DAC directly to the computer.
More than likely, much better depending on your current and previous setup. With a good linear PS the digione is a first class endpoint.
 

mindbomb

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#18
How do you measure THD+N with a headphone?

Focal Utopia has a large change in impedance at the primary resonance which puts a lot of stress on an amplifier. While the Hifiman HE1000 planar magnetic headphone is not that sensitive it's flat impedance makes it an easier load.
I think you can just connect a scope in parallel with the headphones to check their effect on the amplifier.

I did read the Benchmark stuff about this, but I am not clear on what causes the higher amplifier distortion with dynamic headphones.
 
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amirm

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#19
How do you measure THD+N with a headphone?

Focal Utopia has a large change in impedance at the primary resonance which puts a lot of stress on an amplifier. While the Hifiman HE1000 planar magnetic headphone is not that sensitive it's flat impedance makes it an easier load.
Simple. I connect the headphone and then measure the output of the DAC (NOT the headphone) with that load in place Compared to a resistive "dummy load" the headphone provides a complex, frequency varying load.

Here is the Benchmark Media white paper on it: https://benchmarkmedia.com/blogs/application_notes/12838141-headphone-amplifiers-part-1
 

amirm

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#20
What do you exactly mean by the custom driver? Because the Schiit Bifrost and the RME ADI-2 DAC also require drivers to be used on Windows.
Schiit is plug-and play on my Windows 10 Creator's Edition machine as are their other DACs I have tested. If RME ADI-2 needs one, I will ding that just the same. :D

Really the only excuse for having a driver, i.e. Windows support, has gone away. Drivers provide no value for users and only aggravation. The person who loaned it to me said that the drivers he downloaded would not work for him and he had to get a different version after contacting them. Imagine buying a new Windows laptop, going on a plane, only to find out you didn't install drivers.
 
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