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Review and Measurements of Chromecast Audio Analog Performance

amirm

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#1
This is a follow up to my review and measurements of Google Chromecast Audio's digital performance. As mentioned there, the Chromecast audio is a streaming device with integrated DAC. In the other review, I measured its Toslink digital output for usage with an external DAC. Here, I will be evaluating its analog output performance in case you want to forego the external DAC.

As noted there, the casting functionality of Chrome browser is poor and not bit-exact. So for this testing, I used Roon to play the test files and cast them to Chromecast Audio. This allows bit-perfect functionality so that we can see the performance of the hardware in best light.

The measurements are not extensive as with the digital output because my audio analyzer can't control the Chromecast Audio. But there is enough here to get a good idea of how well it does.

Measurements
As usual, let's feed the unit a 1 kHz tone at 44.1 kHz, 0 dBFS (full amplitude) and see how she does:

Google Chromecast Audio Analog Output Dashboard Measurement.png


We have near nominal output of 1.973 volts which is nice. This means there should be no problem driving your amplifiers to their maximum power.

Distortion is respectable resulting in SINAD (signal over power of distortion and noise) of 91 dB. Here is how that ranks among recently reviewed gear:

Google Chromecast Audio Analog Output SINAD Measurement.png


It is well short of even cheap desktop DACs like Topping D10 but not bad either.

Dynamic Range which is a test of playing (almost) nothing versus maximum signal follows the same suit:
Google Chromecast Audio Analog Output Dynamic Range SNR Measurement.png


Jitter and noise is also uneventful:
Google Chromecast Audio Analog Output Jitter Measurement.png


Yes, we have some jitter spikes around our main tone (symmetrical spikes) but because their levels are very low and so is their frequency, they will most likely be perceptually masked. There is some mains leakage coming from the switching power supply I am using to drive it but again, levels are pretty low at -110 dB and lower.

Conclusions
There appears to be nothing broken in the design of the Chromecast Audio DAC as long as you use the right software to drive it. While performance falls in the bottom third tier of tested audio products, it gets there without any drama or obvious faults.

For $35, you get a DAC and streaming functionality built it. As such, the Google Chromecast Audio easily gets my recommendation!

Seeing how you can improve its performance anytime with the use of a good DAC, it is hard to go wrong. You get to put your computer in a different place than your audio system and then stream what you want using Chromecast Audio. With a system like Roon where you can have multiple concurrent playback threads, this would make for an excellent secondary use/room.

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

If you like this review, please consider donating 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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#2
Was the full dynamic range option enabled on the CCA during this test? The setting is automatically enabled when TOSLINK is connected even though the option disappears.

Also, was the included power supply used for this test?
 

amirm

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#3
I am using Roon for playback which sends the bits as is, so dynamic range compression is not in play.

I don't know where its power supply is. :) I am using another switching one.
 
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#4
I am using Roon for playback which sends the bits as is, so dynamic range compression is not in play.
Full dynamic range is a feature of the CCA that's disabled by default. It can be enabled in the Google Home app (screenshot attached).

I don't know where its power supply is. :) I am using another switching one.
If we're being picky, this has the potential to affect the results. Either way, thanks for confirming.
 

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folzag

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#5
Apologies if this is a little too orthogonal to the topic at hand, but it seemed to fit in regard to a device with its primary claim to fame being cost.

Is there a simplistic mapping of SINAD to bit depth? For instance, given 16 bits, what is the minimum SINAD, above which the DAC can be considered "transparent"? How much SINAD is required for each additional bit?

And the (maybe) non-obvious follow-up: is there a simplistic mapping of SINAD to dynamic range? For instance, if I'm listening to a 24 bit, high-res song, albeit with DR8, what SINAD is really required for the DAC to be "transparent"?

If these questions are fundamentally wrong, please clarify, as that would mean I've missed understood something fairly important.
 

amirm

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#6
Is there a simplistic mapping of SINAD to bit depth? For instance, given 16 bits, what is the minimum SINAD, above which the DAC can be considered "transparent"? How much SINAD is required for each additional bit?
Sure. Subtract 1.76 from SINAD and then divide by 6 to get effective number of bits:

1536896781324.png


And the (maybe) non-obvious follow-up: is there a simplistic mapping of SINAD to dynamic range? For instance, if I'm listening to a 24 bit, high-res song, albeit with DR8, what SINAD is really required for the DAC to be "transparent"?
No, you can't relate these two. The DR metrics are heuristically based values. In case of DR meter, it creates a histogram of loudness levels and picks some number of them, averages them and compares to second loudest peak (or something like that). In that regard, it is creating a single number for the entire track.

The DAC does not see music that way. It has to reproduce the quietest and loudest peaks individually. Regardless of the distribution of music loudness, we need to be able to reproduce the faintest signal faithfully regardless of how common that is in the track. As such, you can't use DR values to judge how much through dynamic range/SINAD you need.
 

folzag

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#7
Thx. I had misunderstood DR. I thought it was the difference between the loudest sample and the quietest sample in a given song, with some extra fudge-factors to account for non-linearity of hearing perception.
 
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#8

amirm

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#9
Adding on, there is no simple way to determine the lowest amplitude music signal. For one thing, there is digital mute sometimes at the beginning or the end of the track which would be a false metric to use. On the other hand, music could be below the noise level. And distinguishing noise from music can be hard.

The only method is a statistical one where you have to determine what is noise and what is music.

So in a nutshell, you can't determine the actual dynamic range of music.
 

Jimster480

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#10
Wow I'm glad you did actually test this. I was just thinking about asking you to test this!

For $35 this is one hell of a useful unit! I'm glad to see that its performance is acceptable (especially at this price point).
 

folzag

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#11

jpo

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#12
Hi... first post here. I only signed up to talk about CCA. I think is a game changer and love to see reviews like this one... Thanks!

My opinion: after fiddling with it, and trying it through a Chord Mojo, and then bypass it to listen directly without finding noticeable differences with my 37 y/o ears. I have very good stereo setup (custom made, but i think there are about 10kusd just in components)... and i find its amazing that the analog chain of my setup is just the chromecast audio and tidal. Now i'm evaluating if tidal + roon or just tidal will be good enough.

Amir, you were about to measure that on the other CCA thread. Can you please update us with results? thanks for the good work and cheers from Chile!
 

amirm

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#13
Amir, you were about to measure that on the other CCA thread. Can you please update us with results? thanks for the good work and cheers from Chile!
Hi and welcome to the forum. Unfortunately I have so much new stuff to test that I have not gotten around to doing this.
 
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