Bad quality when using airplay on Airport

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thewolfro Author

Level 1

4 points

Bad quality when using airplay on Airport

Hi Gurus,

I have the following system:

Mac Mini

Anthem MRX310

B&W CM9 S2.

Airport Express

The Mac Mini is connected to Anthem Amplifier via HDMI.

The Airport Express is connected to the Anthem Amplifier via Optical cable.

When i am using iTunes on my mac mini to play music i get good quality (playing via HDMI) .

However when i am trying to play the same songs from my iPhone via the Airport Express the quality is very very bad.

I downloaded the songs on iPhone so i am able to play the songs offline also but i did not see any improvement. The sound is super muffed and the bass is covering/overlapping everything else, sound is flat.

Next thing i tried to use airplay to play the song from the MacMini and i have seen the quality is the same as when i am playing the song from iPhone.

So i think the issue is with the Airport. Is there any sort of processing that the Airport is doing via optical output? Some option i can turn off maybe on the airport?

Thanks in advance!

Posted on Feb 11, 2016 2:24 AM

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Answer 1

Tesserax

Level 10

148,423 points

Feb 11, 2016 9:13 AM in response to thewolfro

Is there any sort of processing that the Airport is doing via optical output?

Yes, but it's not the AirPort, it's the process of using AirPlay for streaming. There are no options on the AirPort that you can change.

The audio output on the headphone/line/HDMI output jack on the Mac is different that the audio output on the AX, specifically on the analog side.

For analog audio, the Mac provides a higher quality output via a 24-bit/44.1-192 kHz DAC. The AX uses a 16-bit Texas Instruments PCM2705 DAC.

For digital audio, I believe the Mac supports both 24-bit stereo with anywhere between a 44.1 to 192 kHz sampling rate. It also supports at least two types of signals: encoded digital audio (aka Dolby Digital and DTS) and two-channel linear PCM, which as you know is just a stereo signal carried digitally over optical fiber.

For the AX, audio input is primarily provided by iTunes. Of course, it can also get input from other sources like Rogue Amoeba's Airfoil.

iTunes does most of the work. When iTunes plays back standard audio content (AAC, MP3, audiobooks, Internet music streams, etc., it decompresses those file formats and creates what's essentially a raw, uncompressed audio stream. That stream is compressed using Apple's Lossless Compression (via a QuickTime codec), encrypted, and then, streamed (via AirTunes/AirPlay) to the AX. The AX decrypts the stream, decodes it, and outputs it in either analog format or as a digital PCM stream.

If iTunes is playing back a digital multichannel file format like AC3 (Dolby Digital) or DTS, those bitstreams (like the lossy formats) are wrapped in Apple's Lossless compression, encrypted, and then, streamed to the AX. In these cases, the AX would first decode the stream, and then, output the raw AC3 or DTS stream via its optical digital audio port.

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