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Universal Audio Apollo X16 Review

amirm

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This is a review and detailed measurements of the Universal Audio Apollo X16 Interface (ADC, DAC and DSP). It was kindly sent to me by the company for testing and costs US $3,499. The X16 is the longest requested interface for us to measure going back to when I had barely started measuring audio electronics. Interest was driven by seemingly impossible distortion and noise specifications. So it is very fortuitous that we finally get to test it.

The X16 is designed for rack mounting:

Universal Audio UA Apollo X16 Review.jpg


The only computer interface is Thunderbolt ()TB). It was hell getting TB capability on my PC motherboard. Once there, I had to buy a cable which at $40 (from Apple) for a 2.5 foot version, was outrageous. Then again the interface is running at ultra high-speed with very low latency so the passive cables are short by definition. This made it hard for me to see the display on the unit so I have no feedback on it. However, I did use the extensive software package/control that came with the unit, to the tune of 600 megabytes!

As the name indicates, you have 16 channels in and out:

Universal Audio Apollo X16 Review Back Panel Power Supply.jpg


DB-25 connectors are used so if you don't have such break out "snakes," you need to buy them as I did. They are commonly available. Just make sure the mating is correct. Mine was a no name $50 one for the ADC portion which worked fine. For the DAC functionality I used the additional monitor out so didn't need to buy that snake.

As you see, a hefty external power supply is used, reminding me of the original Xbox power supply. Not that you would want to mess with replacing it but note that it mates with a 4 pin, XLR like DC connector to the unit.

I ran into a major stumbling block in testing the X16 in that it only exposes an Audio interface for 64 bit applications. The Audio Precision software is 32 bits so would not see it at all. My Roon player did as did Adobe Audition. If you are going to use this for hi-fi applications, be sure your app is 64 bits. My solution to testing was using the AES input on the X16 for most of the measurements. I provide a dashboard readout using Thunderbolt by playing the test tone using Roon player.

This review is focused on electronic performance of the X16. There is tons and tons of functionality in the X16 that I won't touch on, nor am I qualified to do so. Please seek out other reviews for that functionality which is likely responsible for good bit of cost of this unit.

Lots of programming capability exists to set up the unit. Per recommendation from UA, I set the unit to 24 dBu output. The default is 20 dBu, with the extra voltage left for headroom. Fortunately performance is just as good at 20 dBu.

FYI I reviewed the measurements with UA and they are fine with the results.

Apollo X16 Measurements: DAC
Let's start with our usual dashboard pushing bits using Thunderbolt:
Universal Audio UA Apollo X16 Thunderbolt Audio Measurements.png


Note that I have heavily reduced the output level to our standard 4 volt output. We get stellar distortion rating of -135 dBFS (20 dB below threshold of hearing). Being designed for higher output voltage, the SINAD which includes noise and distortion, is excellent but slightly below the best we can get on our desktop DACs:

Best Audio Interface Measurement.png


If we untie the wings from the X16 however to push higher output level, it reaches the same heights:

Universal Audio UA Apollo X16 AES THD+N vs Output Level Audio Measurements.png


SINAD is now clocking at 120 dB. Note that this is driven by the sum of the Audio Precision analyzer noise and X16. If you subtract the former, you get close to what the company has specified (123 dB THD+N).

Performance is same for AES/EBU digital input:

Universal Audio UA Apollo X16 AES Audio Measurements.png


I ran into another common bug in Audio Precision software in that it has some kind of buffer underrun which drops bits. This causes the measurements to get corrupted. To avoid this, I had to turn off averaging to get a single snapshot so ignore the more busy noise floor of the FFT. As you see, performance is identical so we will use AES from here on.

Here is our dynamic range:
Universal Audio UA Apollo X16 AES Audio Measurements Dynamic Range.png


Company spec is 127 dB but it is with a-weighting.

Distortion is kept to a minimum especially in low frequencies where there is usually a rise:
Universal Audio UA Apollo X16 AES Audio Measurements Multitone.png


Intermodulation distortion vs level naturally varies a bit depending on the output voltage:

Universal Audio UA Apollo X16 AES Audio Measurements IMD vs Level.png


Linearity is absolutely nailed:

Universal Audio UA Apollo X16 AES Audio Measurements Linearity.png


Filter response is typical but with excellent attenuation:

Universal Audio UA Apollo X16 AES Audio Measurements Filter Response.png


As you see, the bottom fell out of the graph!

Jitter and spurious tones are of course kept under control regardless of input type:
Universal Audio UA Apollo X16 AES Audio Measurements Jitter.png


Finally, a very clean THD+N versus frequency despite its much wider 90 kHz bandwidth:
Universal Audio UA Apollo X16 AES Audio Measurements THD+N vs Frequency.png


Apollo X16 Measurements: ADC
For the target market, analog conversion is everything so let's see our dashboard there:

Universal Audio UA Apollo X16 ADC Measurements.png


This places the X16 high on the ladder but not the top:

Best audio interface review.png


Sweeping the input level shows that this is about the best we can get:

Universal Audio UA Apollo X16 ADC THD+N vs Level Measurements.png


Notice the very low noise level (SINAD above is dominated by distortion). You can see this in better dynamic range than SINAD:

Universal Audio UA Apollo X16 ADC Dynamic Range Measurements.png


Here is a drill down of a 1 kHz tone relative to RME ADI-2 Pro (non-FS version):

Universal Audio UA Apollo X16 ADC 1 kHz FFT Spectrum Distortion Measurements.png


As you see, it is the third harmonic which holds the X16 back (in red). On others it tends to be lower.

At lower than max input, the X16 competes at the top of the class:
Universal Audio UA Apollo X16 ADC IMD Measurements.png


I had no luck trying to get the ADC to operate at higher sample rates even though I changed it to higher values. Likely an operator error. So this test of frequency response is not that meaningful:

Universal Audio UA Apollo X16 ADC Frequency Response Measurements.png


Finally, here is our THD+N versus frequency:

Universal Audio UA Apollo X16 ADC THD+N vs Frequency Measurements.png


The much better results once again indicates a clean response above the audio band.

Conclusions
It would have been a watershed event if we had tested the X16 when it came out as it would left all of our high-fi DACs in the dust. In the interim period those companies razor focused on best measured performance and given us incredible performance. Still, the X16 if left to produce its high output, is able to keep up with them and of course provide incredible amount of additional functionality to say nothing of 16 channels input and output.

The high output of X16 should allow you to drive amplifiers such as Purifi and Hypex without their input buffers and get better measured performance than you can with high-fi DACs. But do keep in mind the complexity of using Thunderbolt for interface/programming and need for 64-bit player application.

It is my pleasure to put the Universal Audio Apollo X16 on my recommended list.

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

Man, this garden of ours is refusing to give up this year. Went to the greenhouse expecting everything to have died down but instead, found a great bounty of peppers (Shishido, Bell and Banana), cucumbers, and tomatoes:
Greenhouse tomato and peppers.jpg


Made a tuna salad with the cucumber and tomatoes and it was sublime! The fresh and great scent of the cucumbers took me back to wonderful days of summer!

Appreciate any donations using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 

da Choge

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Amir:

The Thunderbolt input panel looks like it could be modular. Do you know if there are any other options?
 
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amirm

amirm

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Blumlein 88

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Excellent! And hey $3500 for 16 channels is only $219/channel and that includes a channel of ADC and DAC. Plus this unit will do lots, and lots of other stuff beyond just playing the music.

https://www.uaudio.com/audio-interfaces/apollo-x16.html

It has tons of high quality plug in emulation of all sorts of analog gear.

I think it was first out in late 2012 or 2013 using Firewire 800 or Thunderbolt. Current ones are Thunderbolt 3.
 
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amirm

amirm

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#7
Awesome results, thanks for testing this. I would of asked the company to of included the breakout cables though. Maybe they can also send you some of their other well used products such as the Apollo Twin which I see heavily used in the field.
 

Dave Tremblay

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#8
I do not. @Dave Tremblay can you answer?
It is modular, but primarily to track with changes to Thunderbolt over time. When we came out with Apollo originally, this was a Firewire card. We no longer support that. But I believe we've had 3 revisions of Thunderbolt cards for TB1, TB2, and TB3. For all of our rack devices that share this design, you could buy a new card as the Thunderbolt spec was updated. These are expensive devices, and an investment for most people, so we don't want to be at the whims of the consumer electronics industry.
 
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It is modular, but primarily to track with changes to Thunderbolt over time. When we came out with Apollo originally, this was a Firewire card. We no longer support that. But I believe we've had 3 revisions of Thunderbolt cards for TB1, TB2, and TB3. For all of our rack devices that share this design, you could buy a new card as the Thunderbolt spec was updated. These are expensive devices, and an investment for most people, so we don't want to be at the whims of the consumer electronics industry.
Any plans on a USB card? The Lynx converters are modular too and can be configured USB, Thunderbolt, DANTE, etc. You guys always seem to have been hell bent on thunderbolt.
 

Dave Tremblay

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Any plans on a USB card? The Lynx converters are modular too and can be configured USB, Thunderbolt, DANTE, etc. You guys always seem to have been hell bent on thunderbolt.
I can't speak to product plans, but it's worth noting why we like Thunderbolt.

1) Thunderbolt can support lower latencies that USB. Latency being the time delay to go through ADC, pass it into the computer, get it back out the DAC. For mastering, or a playback device, this wouldn't much matter, but for tracking audio in a studio, latency is big deal.

2) Thunderbolt is higher bandwidth. For most audio devices, the difference between USB3 and Thunderbolt is irrelevant, but we have 6 DSP processors on this device that can support hundreds of streams of audio in/out of your DAW in a recording environment.

3) This last one is that Thunderbolt supports peer-to-peer communications between our devices. Apollo is a modular system. If you want to have 8 Mic Preamps, 16 other line inputs, and a couple of instrument inputs on your desk, you can buy an Apollo x8p, Apollo x16, and an Apollo Twin x, and we aggregate all of those devices together into one IO. We can send low latency audio between the devices without even making it into Macos or Windows. And not only can we aggregate IO, we also sync the clocks across all of the devices, again because we can communicate peer-to-peer. You cannot do this with USB.

We do make USB devices like our Apollo Solo USB and our Apollo Twin USB for people who just want a single desktop device.
 

Matias

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We do make USB devices like our Apollo Solo USB and our Apollo Twin USB for people who just want a single desktop device.
Do they measure like the X16 too? That would be interesting.
 
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I can't speak to product plans, but it's worth noting why we like Thunderbolt.

1) Thunderbolt can support lower latencies that USB. Latency being the time delay to go through ADC, pass it into the computer, get it back out the DAC. For mastering, or a playback device, this wouldn't much matter, but for tracking audio in a studio, latency is big deal.

2) Thunderbolt is higher bandwidth. For most audio devices, the difference between USB3 and Thunderbolt is irrelevant, but we have 6 DSP processors on this device that can support hundreds of streams of audio in/out of your DAW in a recording environment.

3) This last one is that Thunderbolt supports peer-to-peer communications between our devices. Apollo is a modular system. If you want to have 8 Mic Preamps, 16 other line inputs, and a couple of instrument inputs on your desk, you can buy an Apollo x8p, Apollo x16, and an Apollo Twin x, and we aggregate all of those devices together into one IO. We can send low latency audio between the devices without even making it into Macos or Windows. And not only can we aggregate IO, we also sync the clocks across all of the devices, again because we can communicate peer-to-peer. You cannot do this with USB.

We do make USB devices like our Apollo Solo USB and our Apollo Twin USB for people who just want a single desktop device.
I was only asking because you decided to make the card modular and the competition has a similar modular system but provides other options besides just Thunderbolt. I mainly use AES/EBU myself.

Thunderbolt has always seemed to me to be a more Macintosh thing, whilst most PCs are stuck with USB. This may be okay because most studios prefer Mac but you should provide options and also cater more towards PC users as well. One of the reasons I avoided the Apollo Twin is because thunderbolt only, yes I am aware there is a USB version now.. but still. USB seems to be a niche thing for you.
 

dfuller

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#17
This is, in a phrase, damned impressive. Hats off to UA for this one.
 
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Company spec is 127 dB but it is with a-weighting.
"Flagship conversion with 133 dB D/A dynamic range" even if that is a-weighted seems a bit high compared to the results?

pro gears never use fancy chips, this is es9018 i guess
Lynx Hilo beat it in SINAD with a ADC chip from 2005. Implementation is key, although this is 16-channels here so forgiven a little. :)
 
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