Phone w/subsonic client to Airport Express to DAC

[bupkis]

I use Play:Sub on my phone to stream from my remote Subsonic server. At home, I stream via airplay to an Airport Express.

I know that if I use the optical toslink output from the Airport Express, it will send out a bitperfect stream to an outboard DAC.

What I'd like to know is: Is what Play:Sub or other iOS/Android clients stream to the Airport Express also bitperfect? In other words, say I've got a FLAC or ALAC file on the server. If I use my phone to play it through headphones, obviously it uses the phone's DAC. And, obviously, if using Airplay, it sends some digital signal to the Airport Express wirelessly. Is that digital signal 16-bit/44.1Khz bit perfect?

If not, is there some way to make sure that my outboard DAC is doing the conversion while still using my phone and Airport Express (i.e., short of streaming from a computer hard-wired to it via USB)?

[josquin]

As your concern seems to be quality, I would not use a phone in anyway of the chain since you don't have any control on what is done to the sound.

Imho you should better install a piece of hardware dedicated to pass your stream in a bit perfect way to your DAC. It could be an old PC or a raspberry pi with either Volumio modern dedicated player based on mpd (multiroom / modern UI) installed on it or any distro including Logitech Media Server like daphile (x86) or DietPi(raspberry)

You will then have to install and configure their respective plugin to connect to your subsonic server
For Volumio you will have (for now) to install it manually (quiet simple) instructions here
For LMS you will have to install the plugin SqueezeSonic from the plugin pan in the "3rd party plugin" section

have a good day

[bupkis]

As your concern seems to be quality, I would not use a phone in anyway of the chain since you don't have any control on what is done to the sound.

Thanks for your reply and the interesting information. I didn't know about Volumio. Unfortunately, I don't have any spare hardware, though I suppose I could get a Raspberry Pi.

However, I'm not sure you're right about the phone. There's no reason for an iPhone connected to an Airport Express to do any DA conversion of tracks on the phone itself, which is why the AX has an onboard DAC. And I'm pretty sure that the AX will simply pass on those bits and bypass its own DAC if a toslink cable is attached to it. The question is, are play:Sub or other app-based players on the phone just sending the bits of the track over to the AX or are they processing those bits in some way? You seem to be suggesting their adulterating the bits, but in what way?

[timlance]

I once had a convo with the Play:Sub developer about something or other during which something similar did come up. Best as I can remember he said, in this threads vernacular, bits were not processed, just passed.

I suggest you communicate directly with him. He is easily one of the most responsive developers.

[josquin]

As your concern seems to be quality, I would not use a phone in anyway of the chain since you don't have any control on what is done to the sound.

Thanks for your reply and the interesting information. I didn't know about Volumio. Unfortunately, I don't have any spare hardware, though I suppose I could get a Raspberry Pi.

However, I'm not sure you're right about the phone. There's no reason for an iPhone connected to an Airport Express to do any DA conversion of tracks on the phone itself, which is why the AX has an onboard DAC. And I'm pretty sure that the AX will simply pass on those bits and bypass its own DAC if a toslink cable is attached to it. The question is, are play:Sub or other app-based players on the phone just sending the bits of the track over to the AX or are they processing those bits in some way? You seem to be suggesting their adulterating the bits, but in what way?

Well SmartPhone are tiny pieces of optimized hardware, with an enormous number of functions and capabilities, they are designed to run outdoor and are energy limited. To achieve those technical prowess constructors have to optimized everything. Easy to figure that the less you do the more the battery live. They build proprietary chips with a maximum of hardcoded functions.. You may ask Apple about the sound processing inside their phones, i will be very interested in the answer, in case you got one.
Whatever we are pretty far from the big, heavy, armored, dedicated boxes hi-fi guys are fan of.
Furthermore the AX is limited to 16bits, and even if it's look perfect on the paper, in the real world tos-links connection are imperfect and generates bit loss, for spdif, digital RCA is better.

In anycase the best you can do is try yourself. The only arbiter is what you feel and ear in front of your speakers.

Welcome in the hi-fi world and good luck

jo