Apple TV 3'rd Generation - AirPlay measurements over TOSLINK

[jjk1]

I have a couple of modern ATVs and they pass 24bit audio over hdmi through to a wiim pro plus and out to a DAC that reports a 24 bit lock.
the ATV gen 3 Model A1469 does the same thing over optical and hdmi passed through the Wiim over hdmi reporting 24bit crossed over or directly to the end DAC via optical or coax bridge or with the optical on the ATV connected directly to the end DAC.
The ATV gen 3 model A1427 will only pass 16 bit audio.
all tests done with airplay (iOS version does not matter on a stream. I have iOS as old as 12.5.7 and the end DAC behaves the same regardless or iOS version requesting the stream.)
It feels like a hand off rather then an iOS to ATV presistant airplay connection but I have no idea if the master is decided based on the device, or if the device is converting formats not just sample rates?

I think you get what you see. Apple giveth features but the never taketh away or if they do it’s through well planned obsolescence.
Once configured and headless - mayby the A1469 version of the ATV is as close to an in the home apple optical dongle as I will ever find. I want all can find at 20$ a pop. Someone with wire shark could measure bit counts but my wife would flip if I did that. I’m retired and have divorced myself from such activities

 

[mdsimon2]

@jjk1 Your experiences don't quite match my testing. Even if your DAC reports 24 bit, I've never seen anything streamed over AirPlay actually clear 16 bit performance on either the A1427 or A1469. Although I wouldn't be surprised if the AppleTV output is 24 bit as the performance when using volume control seems to suggest this. I made some measurements of the A1469 showing this behavior here -> https://www.audiosciencereview.com/...-resolution-16-bit-or-more.47586/post-1707076.

If your A1427 is not showing 24 bit output maybe you have the output set to 16 bit?

Both the A1427 and A1469 are capable of 24 bit performance if streaming files via Home Sharing, although it is clear that everything is resampled to 48 kHz and how well it does this depends on the file sample rate.

Here are a few digital measurements of the A1469 using Home Sharing, the A1427 measurements are identical.

1 kHz - 0 dBFS - 24 bit - 44.1 kHz file sample rate (recorded at 48 kHz)

1 kHz - 0 dBFS - 24 bit - 48 kHz file sample rate (recorded at 48 kHz)

1 kHz - 0 dBFS - 24 bit - 88 kHz file sample rate (recorded at 48 kHz)

1 kHz - 0 dBFS - 24 bit - 96 kHz file sample rate (recorded at 48 kHz)

This gives me hope that using apps on the AppleTV may allow for 24 bit audio, although short of having hi-res test tones on a streaming service app I am not sure how I would test this. Either way, 16 bit audio is good enough for me.

Michael

 

[jjk1]

@jjk1 Your experiences don't quite match my testing. Even if your DAC reports 24 bit, I've never seen anything streamed over AirPlay actually clear 16 bit performance on either the A1427 or A1469. Although I wouldn't be surprised if the AppleTV output is 24 bit as the using volume control seems to suggest this. I made some measurements of the A1469 showing this behavior here -> https://www.audiosciencereview.com/...-resolution-16-bit-or-more.47586/post-1707076.

If your A1427 is not showing 24 bit output maybe you have the output set to 16 bit?

Both the A1427 and A1469 are capable of 24 bit performance if streaming files via Home Sharing, although it is clear that everything is resampled to 48 kHz and how well it does this depends on the file sample rate.

Here are a few digital measurements of the A1469 using Home Sharing, the A1427 measurements are identical.

1 kHz - 0 dBFS - 24 bit - 44.1 kHz file sample rate (recorded at 48 kHz)
View attachment 320471

1 kHz - 0 dBFS - 24 bit - 48 kHz file sample rate (recorded at 48 kHz)
View attachment 320472

1 kHz - 0 dBFS - 24 bit - 88 kHz file sample rate (recorded at 48 kHz)
View attachment 320473

1 kHz - 0 dBFS - 24 bit - 96 kHz file sample rate (recorded at 48 kHz)
View attachment 320475

This gives me hope that using apps on the AppleTV may allow for 24 bit audio, although short of having hi-res test tones on a streaming service app I am not sure how I would test this. Either way, 16 bit audio is good enough for me.

Michael

Yeah - this particular ATV (and new models I guess) output 24bit - what’s in it I don’t know but these are airplay1 so at least 96db of range CD quality on 24bit volume control all the way to every speaker I want without at HDMI or a tv screen If I choose. It makes airplay for Apple Music at least as good as airplay for apples own competition in the streaming space. I never understood why the don’t just give you easy digital options. The 24bit lock that I get from the A1469, and the 16bit lock I get when set up exactly (yes - not set to 16bit) is what is interesting- is the a1427 doing 24bit or 16bit volume control- its what I’ve never been able to determine and why I want to know how much dynamic range I have and where so I can use my thumb for volume control

 

[mdsimon2]

s the a1427 doing 24bit or 16bit volume control- its what I’ve never been able to determine and why I want to know how much dynamic range I have and where so I can use my thumb for volume control

This is what I used for the measurements -> https://hifimediy.com/product/hifime-ur23-spdif-optical-to-usb-converter/. Less than $50 and you could find out.

Like I said, my A1427 does 24 bit output, but if your DAC is reporting 16 bit I would imagine that it is only sending 16 bit.

Here are some measurements from my A1427.

1 kHz - 0 dBFS - 24 bit - 48 kHz file sample rate (recorded at 48 kHz)

1 kHz - 0 dBFS - 24 bit - 88 kHz file sample rate (recorded at 48 kHz)

1 kHz - 0 dBFS - 24 bit - 44 kHz file sent via Airplay at full volume (recorded at 48 kHz)

1 kHz - 0 dBFS - 24 bit - 44 kHz file sent via Airplay at -29.9 dB volume (recorded at 48 kHz)

Michael

 

[jjk1]

This is what I used for the measurements -> https://hifimediy.com/product/hifime-ur23-spdif-optical-to-usb-converter/. Less than $50 and you could find out.

Like I said, my A1427 does 24 bit output, but if your DAC is reporting 16 bit I would imagine that it is only sending 16 bit.

Here are some measurements from my A1427.

1 kHz - 0 dBFS - 24 bit - 48 kHz file sample rate (recorded at 48 kHz)
View attachment 320498

1 kHz - 0 dBFS - 24 bit - 88 kHz file sample rate (recorded at 48 kHz)
View attachment 320500

1 kHz - 0 dBFS - 24 bit - 44 kHz file sent via Airplay at full volume (recorded at 48 kHz)
View attachment 320501

1 kHz - 0 dBFS - 24 bit - 44 kHz file sent via Airplay at -29.9 dB volume (recorded at 48 kHz)
View attachment 320502

Michael

Thank you - light dawns over marble head.

 

[jjk1]

FYI - I was able to get both the ATV 3rd gen A1427, and A1469 to light lock the DAC at 24bit when streaming via airplay from Apple Music on any iOS device with optical output. In my case the settings in the ATV is Dolby “on“ in the A1469, and Dolby “Auto” on the A1427.
PCM extraction solved. 24bit digital volume control solved.
thanks for the review again!

 

[Miniyouuuu]

No real specs of AppleTV 4K?
I never use AppleTv volume control. I teach remote control to raise and lower the amp volume control.

 

[jjk1]

No real specs of AppleTV 4K?
I never use AppleTv volume control. I teach remote control to raise and lower the amp volume control.

Yes - ultimately the amp controls the volume but with the ATV 3 running 24bit volume control on its optical output you can control all that Apple Music has to offer but without the need for an hdmi connection and it gives you 24bit CD+ 2channel PCM set free in your audio network Without a dedicated iOS or Apple speaker like a HomePod that has no pre outs, and it gets you past the airplay2 256/16 limitation. The only thing it can’t do (or I can’t make it work) is to airplay from the ATV 3 to another ATV.

 

[mdsimon2]

Even if your DAC reports 24 bit, I've never seen anything streamed over AirPlay actually clear 16 bit performance on either the A1427 or A1469.

Maybe some folks already know this as I've lost track of all the things that need to be done to get the best performance out of AirPlay these days, but if you play a file via QuickTime and select the AppleTV from within QuickTime you can use AirPlay and retain 24 bit performance.

You will know it is working if you lose the volume control on QuickTime, also if you had selected your AppleTV as your main system output it will no longer be selected.

The performance seems just as good as using the Computers (home sharing) functionality on an AppleTV.

Michael

 

[trl]

@mdsimon2 how did you got the -144dB THD+N, please? That's 24-bit audio and I'm trying to understand how is it possible. Have you used UR23 to connect the AirPlay device to TOSLINK and the USB-C plug was inserted in your computer and UR23 was acting like a Digital-to-Digital interface?

 

[mcdn]

All SPDIF communication is 24 bit, which is how devices can do nice digital volume control over it without dithering. Dithering is even better, but at 24 bits it hardly matters for playback.

 

[mdsimon2]

@trl Yes, the measurements were all digital to digital to be better show the results of the resampler, AppleTV TOSLINK output in to a TOSLINK to USB device. The source streaming to the AppleTV was a 2015 macbook pro.

For the first measurements in this thread I used the UR23, for the latest ones I used a MOTU Ultralite Mk5 TOSLINK because it was on my desk.

Michael