Why can't you play Hi-Res audio through the optical (S/PDIF) input of an AVR?

[reverbel]

Hi everyone,

I have a Chromecast Audio (CCA) connected to the optical (S/PDIF) media input of a Denon AVR-X3700H. This setting allows me to stream music via WiFi from my phone to the CCA, which sends the digital audio (over a Toslink cable) to the optical media input of the AVR. The signal conversion from digital to analog does not happen in the CCA, but in the AVR. (I presume this is better than connecting the CCA to the analog AUX input of the AVR, right?)

The arrangement described above works fine for CD quality (16/44.1) audio. It works also for stereo audio with the following bit depth/sampling rate combinations: 16/48, 16/96, 24/44.1, and 24/48. It ceases to function properly at 24/96, in which case there are quite frequent (and very audible!) "hiccups" in the sound. Hence the maximum bit rate accepted by the optical input of the AVR appears to be quite low... I found this strange, as the AVR-X3700H accepts audio with much higher bit rates (5.1 audio, DTS 24/96) via its HDMI input.

In order to check it this was an S/PDIF restriction, I connected the same CCA to the optical input of a Loxjie A30 DAC/amp. It worked flawlessly at 24/96, so the bottleneck indeed appears to be in the optical input of the AVR. Why doesn't it accept audio bit rates comparable to the ones taken by the HDMI input?

 

[Galliardist]

It's a design limit, compounded by all sorts of other things in the engineering. TOSLINK was originally designed to work with 20/48 PCM, so is "extended" to do anything more.

So it can become a "pot luck" thing. It's usually reliable up to 24/48. After that it's anybody's guess what will happen. Different tranceivers built into different devices may or may not talk to each other at higher rates, sometimes you need a better cable (not a sound quality thing: it works or doesn't). A dirty or poor quality plug or socket can cause the issue you have as well.

So clean everything, particularly the connector on the AVR: if that doesn't help, you can use 16/44.1 for all your stereo connections to the Denon and/or try the AUX connector (these options may and probably should not be audibly different).

I've not checked to see if there are any settings in the AVR that may affect results. It's worth checking the manual in case.

If you want to throw some money at the problem, you could consider the WIIM Pro which has Chromecast Audio and a coaxial output which should be more reliable.

 

[Zapper]

Probably because they have an optical interface module that they reuse in every AVR and haven't bothered to update it. Can't you stream over WiFi direct to this AVR?

 

[wwenze]

I've had speakers that can only go up to 24/48

So yea, it's a luck thing, if the SPDIF specs were not specified in the manual.

I'm thinking that maybe somewhere out there is a low-cost SPDIF receiver chip or an optical receiver module that max out at 24/48.

 

[Chrispy]

What happens when you stream via dlna direct to your 3700?

 

[Galliardist]

Probably because they have an optical interface module that they reuse in every AVR and haven't bothered to update it. Can't you stream over WiFi direct to this AVR?

No Chromecast. There's AirPlay 2 and various apps.

HEOS is listed, would be Denon's preferred method for streaming, and is worth a look. The current datasheet lists a lot more streaming services than described elsewhere for the AVR.

The question doesn't specify what is being streamed from the phone, which is of course relevant here if an alternative is acceptable. I've not used HEOS but it doesn't seem to have the greatest reputation for useability, and our OP may have already tried and hated it.

I've had speakers that can only go up to 24/48

So yea, it's a luck thing, if the SPDIF specs were not specified in the manual.

I'm thinking that maybe somewhere out there is a low-cost SPDIF receiver chip or an optical receiver module that max out at 24/48.

It may be to do with the purpose: the only mention of the optical connector in the manual (no spec!) is for use with a TV optical out, and as far as I'm aware all TV optical outs seem to only work to 24/48, so it may be a design limitation in the unit.

 

[reverbel]

It's a design limit, compounded by all sorts of other things in the engineering. TOSLINK was originally designed to work with 20/48 PCM, so is "extended" to do anything more.

So it can become a "pot luck" thing. It's usually reliable up to 24/48. After that it's anybody's guess what will happen. Different tranceivers built into different devices may or may not talk to each other at higher rates, sometimes you need a better cable (not a sound quality thing: it works or doesn't). A dirty or poor quality plug or socket can cause the issue you have as well.

So clean everything, particularly the connector on the AVR: if that doesn't help, you can use 16/44.1 for all your stereo connections to the Denon and/or try the AUX connector (these options may and probably should not be audibly different).

I've not checked to see if there are any settings in the AVR that may affect results. It's worth checking the manual in case.

If you want to throw some money at the problem, you could consider the WIIM Pro which has Chromecast Audio and a coaxial output which should be more reliable.

Thanks, @Galliardist!

I've checked the manual and didn't see any settings that would make the AVR work with higher bit rates through the optical input. Tried direct mode (as it presumably turns off all DSP and therefore requires less processing in the AVR) but there was no improvement.

The WiiM Pro appears to be a great CCA replacement indeed. I've read good things about it and would like to try it at some point. For the issue at hand, however, it is unclear that the WiiM Pro would make a difference, as the AVR documentation says nothing about the bit rates accepted by both the optical and the coaxial inputs.

So for now I'll just use 16/44.1 or 24/48 whenever streaming stereo audio to the Denon. Might also try using an analog (RCA) input, but, as you said, probably there won't be an audible difference. (If neither of the DACs -- the one in the Denon and the one in the CCA -- is too shabby, the difference should not be noticeable.)

 

[reverbel]

What happens when you stream via dlna direct to your 3700?

In this case the AVR works with higher bit rates. I played 24/96 tracks with no problem. According to the manual, 24/192 should also work. I will try 24/192 tracks shortly.

The problem with DLNA is that the AVR doesn't give me a decent UI.

 

[reverbel]

Probably because they have an optical interface module that they reuse in every AVR and haven't bothered to update it. Can't you stream over WiFi direct to this AVR?

Not via Chromecast. As @Galliardist said, HEOS is Denon's preferred method for streaming. The main problem with HEOS is the lack of a decent user interface. And I am an Android user, so AirPlay 2 doesn't help me either.

 

[Chrispy]

In this case the AVR works with higher bit rates. I played 24/96 tracks with no problem. According to the manual, 24/192 should also work. I will try 24/192 tracks shortly.

The problem with DLNA is that the AVR doesn't give me a decent UI.

You get UI with the CCA?

 

[JLGF1]

The problem with DLNA is that the AVR doesn't give me a decent UI.

The UI of the BubbleUpPnp Android client is light years ahead of the Denon HEOS client which is an abomination. Well worth the $5.

 

[reverbel]

The question doesn't specify what is being streamed from the phone, which is of course relevant here if an alternative is acceptable. I've not used HEOS but it doesn't seem to have the greatest reputation for useability, and our OP may have already tried and hated it.

My main usage is streaming audio files that live in an Android phone. I am an avid music listener and I keep most of my music collection in a 1TB microSD card in my phone. I am also a longtime user of PowerAmp, an Android music player with a great user interface. PowerAmp is my preferred way of listening music. Since the music lives in the phone, I can use PowerAmp on-the-go, either within an airplane or on a road which might have no internet available. Occasionally I use Amazon Music, mostly to discover "new" music that I might want to add to my collection.

Both PowerAmp and Amazon Music support Chromecast, so I set up CCAs in audio systems in most places I regularly frequent: living room, bedroom, vacation home, office... Except for the silly AVR restriction, everything works perfectly, even for hi-res music files.

 

[reverbel]

It may be to do with the purpose: the only mention of the optical connector in the manual (no spec!) is for use with a TV optical out, and as far as I'm aware all TV optical outs seem to only work to 24/48, so it may be a design limitation in the unit.

You're probably right, but the manual should convey this information explicitly. And should also inform the bit rates accepted by the coaxial inputs as well.

 

[reverbel]

You get UI with the CCA?

Yes (indirectly), as many (most?) music player apps are Chromecast-enabled. The one I use, Poweramp, is probably the music player with the best user interface. (Well, this is just my opinion, of course, but many people agree with me.)

 

[reverbel]

The UI of the BubbleUpPnp Android client is light years ahead of the Denon HEOS client which is an abomination. Well worth the $5.

I didn't know that one, thanks for the tip! I see that BubbleUpPnp is a DLNA/Chromecast client. Would it work with HEOS, as a replacement for the Denon client? I mean: it can certainly stream over Chromecast, but would it also be able to stream over HEOS, directly (without using Chromecast) to my HEOS-enabled AVR?

 

[JLGF1]

Try it out; ad version is free. It sees my Denon (no Chromecast). It's not native HEOS though, which doesn't matter in my context.

 

[Galliardist]

I didn't know that one, thanks for the tip! I see that BubbleUpPnp is a DLNA/Chromecast client. Would it work with HEOS, as a replacement for the Denon client? I mean: it can certainly stream over Chromecast, but would it also be able to stream over HEOS, directly (without using Chromecast) to my HEOS-enabled AVR?

If I understand it correctly HEOS is proprietary. I have a vague recall of something for it called SHOE.

I presume BubblruPnP is serving as a DLNA server and player? I only knew of it as a player used with a separate server when I tried it years ago.

 

[Chrispy]

Yes (indirectly), as many (most?) music player apps are Chromecast-enabled. The one I use, Poweramp, is probably the music player with the best user interface. (Well, this is just my opinion, of course, but many people agree with me.)

I meant via the avr and with a CCA. The app gui is what it is....

 

[Berwhale]

Since the Denon has HDMI inputs, you could plug a ChromeCast (not CCA) straight into it...

https://support.denon.com/app/answers/detail/a_id/4570/~/setup-procedure-to-cast-spotify%2Cnapster%2C-pandora%2C-and-other-supported-services

I don't know if there are any bit depth or rate restrictions when doing this. A bit of Googling indicates that streaming might be limited to 24/48 for non-Audio Chromecasts. There's also some discussion regarding the use of CC's for audio here: https://www.audiosciencereview.com/...cast-with-google-tv-as-audio-streamers.29078/

 

[TonyJZX]

you shouldnt have issues up to 24/192

i have this running on multiple dacs

funny thing is Toslink came about with redbook so you're looking at tech originating in the early 80s... the fact toslink works at all above 24/96 is a minor miracle... they just keep adding capability not intended for anything more than redbook

BUT to me its one of those techs that should be migrated away from unless you have needs less than than 192 or want zero EMI interference.