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

Source post on Google+

Published by

François Simond

Mobile engineer & analyst specialized in, display, camera color calibration, audio tuning

4 thoughts on “Published yesterday by +iFixit​ :Chromecast 2015 and Chromecast Audio teardowns”

  1. Isolation maybe? The reference design for that buffer circuit has no DC path to ground on either channel, and takes a differential signal from the DAC. They might have been concerned about someone plugging the chromecast into a dodgy speaker system with a ground loop and damaging the device.

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