ChromeCast Audio multi-speaker/multiroom first impressions

I just tried two Chromecast audio for the multiroom feature.
It's easy to setup and works well!

When plugging a pair of analog headphones on each Chromecast, CCAudio1 HP1 on left ear, CCAudio2 HP2 on right ear, matching volumes I wasn't able to discern a phase difference when playing a track on Google play music: great result.

It would be worth trying after a while to see if the Chromecast audio drift and how much: if the reference clocks are the DAC ones without compensation after the initial synchronization, I suppose it will drift at some point.

One limitation I experienced is that the volume was not matched anymore between both headphones after adjusting the group volume.

But still: pretty cool stuff, I think this platform has a promising future!

#supercurioBlog #Chromecast #audio #multiroom


In Album Chromecast audio multiroom first impressions

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Confirmed: Chromecast audio analog output is 48kHz 16-bit today

I gave a hand to +FrAndroid​​​​​ +Manuel C.​​​​​ to explore the audio capabilities of the Chromecast audio.

Google confirmed what we found in measurements earlier: Chromecast audio resamples everything to 48 KHz 16-bit for both the optical and analog output.

– It is a poor default choice for audio since most material is sampled at 44.1 KHz.
– The resampler itself is not so great, introducing various distortion artifacts.
– The 16-bit output limitation is not welcome, including for 16-bit material since the volume control is software and digital.
– And it prevents playing 96 KHz 24-bit material without loss of quality.

Google say they are working on it, however they didn't adjust their marketing material announcing the support of 96 KHz 24-bit resolution which is rather unfortunate.

I have a lot more measurements and data than the graph +FrAndroid​​​​​ republished, would you like to see them?

#supercurioBlog #audio #measurements #chromecast

Test du Chromecast Audio, le parfait compagnon de vos oreilles – FrAndroid
Après avoir rendu intelligents les écrans les plus basiques avec son Chromecast, Google a souhaité aller plus loin cette année avec le Chromecast Audio, un

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Casting lossless audio to Chromecast

+Manuel C. is preparing a Chromecast audio review for +FrAndroid and came to me today to talk about that. I shared my impressions and told him that I didn't find the time yet to develop a mini app based on the SDK to stream lossless audio to it.

So he found this music player, which is one of the first app available able to do just that!
The screenshot shows the upload bandwidth which corresponds to 44100 Hz 16-bit PCM Stereo audio when playing a WAV file for a quick verification.

44100*16*2 = 1411200 bit/s = 172 kB/s: perfect!

The name is Shuttle Music Player, from SimpleCity, by +Tim Malseed


– I noticed already a little bug concerning casting audio volume so be careful with that.
Cool and promising app nonetheless, highly recommended try!
– Keep in mind that the Chromecast Audio and Chromecast 2 currently upsample everything to 48 kHz with a non-optimal resampling algorithm. So there's some loss here unless you're streaming 48kHz/16-bit PCM.

Now I can prepare Chomecast Audio quality measurement, nice!

#supercurioBlog #audio #lossless #Chromecast


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Chromecast audio first impressions

I just received my #Chromecast audio and couldn't resist trying it right away with headphones.

So it's perfectly capable of driving the 300 ohms +Sennheiser​​ HD 650.
The "High Dynamic Range" seems to produce a higher quality with these headphones, the output level also gets several dB higher when activated.
(then at the maximum level, it gives a sound pressure well above the pain threshold, with surprisingly low distortion)
Subjectively it also sounds rather good, which is not the case for every equipment with the HD 650: with its mostly neutral frequency response and low distortion it becomes a lot easier to tell the difference.

A very crude quick test via lossily compressed test samples seem to indicate the presence of some resampling artifacts on 44.1kHz content, none for 48 kHz (needs verification)

Still, it could probably serve as cheap headphones DAC / amplifier for special uses for headphones notoriously difficult to drive, replacing favorably a few smartphones or laptops' audio output.

But please don't take my word on it quite yet, I'll test with more headphones / earphones and also complete measurements.

I might have to write some new code for that however in order to cast lossless audio – apps I found so far use lossy transcoding which is not necessary.

#supercurioBlog #audio

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Published yesterday by +iFixit​ :Chromecast 2015 and Chromecast Audio teardowns

On the audio part, we learn about the CC Audio's DAC setup used to drive the analog output.

The stereo DAC is an AKM AK4430:
– Up to 192kHz / 24-Bit
– 128 times oversampling for 8-48 kHz, 64 times oversampling for 32-96 kHz, 32 times oversampling for 45-192 kHz.
– 2Vrms output with its own charge pump
– 104 dB Dynamic Range
– -91 dB THD+N
– -104 dB crosstalk

Those are fine specs by themselves, but Google decided to add a component in the output path, a +Texas Instruments​ DRV632 Line Driver:
– 105 dB Dynamic Range / SNR
– 0.002% THD+N = -94 dB THD+N
– 2Vrms output with its own charge pump.
– -110 dB crosstalk at 1Vrms output

I'm not exactly sure why this second component is present since the DAC already outputs in 2Vrms, which is what you want for line-output
+Texas Instruments​ lists the DRV632 usages as:
– a way to adjust the output gain (but only via external resistors and not digital)
– line output protection
– short circuit protection
– DAC post-filter (typically as a low-pass)
Based on the DRV632 specs, it should not harm the audio quality.

With a current limit of 25 mA, it should also be capable of driving some small headphones (although it's not designed for that)

Measurements will tell more the actual performance of this analog combo.

About that, Google just notified me of my Chromecast audio's shipment, so I'll try just that after receiving it.

#supercurioBlog #Chromecast #audio #teardown

Chromecast 2015 Teardown – iFixit

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