Originally Posted by gizmofanv
How do compare audio quality between AirPlay and other mode of playback?
I did some research related to this topic:
Airplay itself does not alter music source in any way. It is designed to not degrade the audio at all.
ATV1 can only output 44.1Khz
ATV2 and 3 can only output 48KHz and not 44.1KHz, so ATV2 and 3 converts everything to 48KHz
Would pass 16/44.1 unchanged but would down sample on higher rates. Does not support 24 bits.
Lightning to USB cable does not allow USB audio output
but the CCK (camera connection kit) does support it due to the built-in authorization circuit that interact with the usb codec on iPad but the codec only supports usb 1.1 and may not work for all external DAC.
Would need a FLAC player application, eg. "FLAC Player" or "Golden Ear" on the iPad.
It was said only "FLAC Player" can allow 24/192 on iPad. FLAC Player uses Class 2 audio USB to send up to 24/192 out of the iPad to a Class 2-capable DAC
FYI, iTunes downsamples all music to 16 bit / 41.1 kHz.
Some platforms have miniusb port that supports USB audio output
ie. Samsung Galaxy Tab, Galaxy Note, Nexus
Nexus 7 doesn't support MHL or any video out.
In general, for digital transportation, i.e. sending digital data from one device and receive them on the other device, the first thing to check is if it supports the digital file format (such as flac or others). The second thing to check is if it supports the sample rate and resolution (such 24bits/96KHz) of your files. However, the most important thing as far as sound quality goes is if it alters the digital data in any way. For example, resampling from 44.1kHz to 48kHz, or EQ, or automatic volume control, etc. Since your receiver SC-67/68 already has so much better DAC and digital processing capabilities than any of your iPad/Androd platforms, you do not want to do anything that alters the digital music (such as EQ) on the platform.
In short, digital transportation is just a transportation (see note below). As long as the data is unchanged and not dropped along the way, it is the receiver that matters on the sound quality (assuming the music source itself is good). Airplay is a very good transportation method that does not alter your digital music.
Note: this is in simple and general terms. To be technically correct, there are some other factors in digital transport such as clocking and noise isolation that can affect audio quality.