Airport Express + Cambridge Audio 540R DAC / Amp - Airplay optical output issue

robdrums2097

Active Member
Hi all,

I’m in the process of putting together a simple system for my study, using stuff I already own. It’s to stream either from my computer or AirPlay with the following components:
  • My old Cambridge Audio 540R V2 receiver as a 2 channel amp & DAC
  • Celestion F10 bookshelf speakers
  • Deezer Hi-Fi / Amazon Music HD
  • Apple Airport Express (A1392, the most recent one) for Airplay 2 connected by mini Toslink optical to optical on the amp
  • Dell Windows 10 laptop connected by analogue jack to phono

  1. Ideally I would do most of my streaming from my PC. This is, I believe, my only chance of getting 24 bit music out the other end. However, unlike my older Dell PCs and my old Mac, there’s no SPDIF output so I’m restricted to the probably not brilliant 3.5mm jack output & onboard DAC via its Realtek USB sound ‘card’. Although the whole point was to not spend a penny on the system, I might consider a not-too-expensive USB DAC if it was worth it. This is a company-administered Windows 10 Dell laptop via a Dell WD15 dock. I’m wary that although I can plug USB things like mouses & flash drives in without problem, I may struggle if a USB DAC required drivers or admin login etc. to install. Any recommendations for a DAC (or other suggestions) & if it would likely work would be good.
  2. Airplay is the usually-simpler alternative, and what I use most for music across the house. In this case, it would be via the Airport Express’s mini Toslink output & iOS devices. The Airport has a combined optical / line, but as Airplay will restrict us to 16/44.1 output, I don’t know how much better the Cambridge’s DAC will really be (if at all – it apparently has a Crystal CS42518 24-bit/192 kHz multi DAC, while I don’t know what is in the Airport). However, my main issue currently is that it doesn’t work! The output I can see glows red & it works in analogue mode, but when I connect the optical cable (the only one I have, so it’d cost a few quid to try another lead), I can see red coming out the other end. Yet when I plug it into the 540R, nothing. I’ve tried it in all three digital inputs, and I get no sound at all. No pops, clicks or squeaks - nada. Plugged into my Yamaha sound bar, the Airport works fine by optical. So I’ve ruled out the cable, Airport and streaming source. Better yet, other optical & coaxial sources into the 540R work fine (albeit with a half second ‘Unlock’ delay on most songs). So there doesn’t seem to be a DAC, input or other issue with the amp either. I’ve read some reviews that say the Airport Express suffers from jitter & that some DACs may not be able to cope with that. Is that possible, or just mumbo jumbo? Having ruled out every link along the chain, I’m now at a bit of a loss! Or is it simply not worth the bother given that the Airport’s DAC is probably reasonable and that AirPlay won’t give me anything over CD quality anyway (as I understand it)?

Thanks in advance for any assistance or advice.

Rob
 

alloallo

Novice Member
What is the firmware on your AirPort Express ? If it is 7.8.1, try to revert to 7.6.9 with is the latest firmware before AirPlay 2.
 

robdrums2097

Active Member
What is the firmware on your AirPort Express ? If it is 7.8.1, try to revert to 7.6.9 with is the latest firmware before AirPlay 2.
It is 7.8.1, yes. I might try, though I’ve been using the analogue output & been reasonably happy with the sound. Should Airplay 2 have had any impact on the optical out, you reckon?

Rob
 

alloallo

Novice Member
I tried DTS encoded WAV file streamed to AirPort Express connected with optical output to my home cinema receiver.
With 7.6.9 : DTS is decoded.
With 7.8.1 : only noise.
 

robdrums2097

Active Member
I tried DTS encoded WAV file streamed to AirPort Express connected with optical output to my home cinema receiver.
With 7.6.9 : DTS is decoded.
With 7.8.1 : only noise.
Intriguing, it does appear to work on the older version. My problem now seems to be a physical one where the lead won’t click into the port very well and keeps falling out. Not sure if it’s the socket or the cable, but we have optical sound. Thank you!
 

Cebolla

Member
I tried DTS encoded WAV file streamed to AirPort Express connected with optical output to my home cinema receiver.
With 7.6.9 : DTS is decoded.
With 7.8.1 : only noise.

Interesting, the implication being that the AirPort Express with firmware 7.8.1 AirPlay 2 version wasn't streaming bit perfectly.

AirPlay 2 is supposed to provide guaranteed synchronised audio between sender & receiver(s). Also, AirPlay is known to discard some of the audio data if it's struggling to maintain sync on a particularly poor network connection. This could explain why the encoded DTS may have become corrupted.

Did DTS fail to be decoded every time you tried streaming with the AirPlay 2 Airport Express?
Were either the DTS encoded file playing computer (AirPlay Sender) or the AirPort Express wirelessly connected to the network?
 
Last edited:

robdrums2097

Active Member
Interesting, the implication being that the AirPort Express with firmware 7.8.1 AirPlay 2 version wasn't streaming bit perfectly.

AirPlay 2 is supposed to provide guaranteed synchronised audio between sender & receiver(s). Also, AirPlay is known to discard some of the audio data if it's struggling to maintain sync on a particularly poor network connection. This could explain why the encoded DTS may have become corrupted.

Did DTS fail to be decoded every time you tried streaming with the AirPlay 2 Airport Express?
Were either the DTS encoded file playing computer (AirPlay Sender) or the AirPort Express wirelessly connected to the network?
I still can’t fathom either what AirPlay / Airplay 2 actually has to do with the optical out or why it should be affected, even when playing boggo bitrate Deezer / Spotify streams.
 

alloallo

Novice Member
Same problem if the computer and the AirPort Express are connected via Ethernet cable with wifi disabled.

I tried again today : sometimes I got noise, sometimes the receiver could decode DTS but only for less than a second. I just made this video.

So it may prove the signal is still bit perfect, but there a synchronisation problem.
 

The latest video from AVForums

Podcast: Best Home Cinema Sources and B&W 805 D4 Speaker Review and more...
Subscribe to our YouTube channel
Support AVForums with Patreon

Top Bottom