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Help re Airport Express & Cambridge Audio 840CD Player


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I currently run the following set up:


Apple Time Capsule on which all my Apple Lossless Music Files are stored.


MacBook with only minimal music stored.


Airport Express (n not g version)


840 Cambridge Audio CD Player


I stream my music through to the Airport Express which connects to the 840 player digital optical input.


Recently, I experience occasional distortion or screeching like interference when I play my music for about 10 secs that then goes away. I used to get this in fact even when I stored all my music files on an external hard drive that I connect via firewire to my macbook.


Does anybody have any ideas as to the possible cause of and solution to the problem? I had read on some forums that it comes from itunes vers 8 itself. Is this true?


Would using a 40GB Apple TV as a streamer for Airtunes in place of the Airport Express solve the problem? I have heard of people having problems with Apple TV dropping off the device list on their computers?


Finally I have also read that use a reclocking device improves jitter greatly on the Airport Express? I have seen a reference to the PS Audio Digital Lens? Is there something like this available in the UK and is it a worthwhile purchase?








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At a guess I'd say that your CD player DAC is having occasional problems locking to the digital output from the AE.


Jitter is only an issue for the DAC, so nothing external to it can help.


Losing the AE from the device list is probably a wireless issue. You almost certainly won't have problems using an AE Base station but other routers vary enormously in performance. Also Microwave ovens and other wireless networks nearby may cause drop outs, but none of this will produce the noise you describe which I think is between the AE and the 840CD.


You could always reload iTunes 8, but I've had no problems on my computers and am not aware of any issues with our customers. The 840CD is an excellent machine too, so you could try another optical cable to check it.


Best of luck




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Thanks Ashley.


Actually, it was the Apple TV I tried that dropped off the devices list in Itunes. Apparently this is a very common problem with device and makes me nervous about trying it again. Funny thing, it did not produce any screeching effect in the two week period I tried it. Furthermore I have tried plugging in my macbook to the dac and again no problems. It is only with AE which leads me to believe that the optical signal emitted by the AE is very poor quality. Do you think something like a squeezbox duet would be any better?


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I don't think it is an Apple TV fault because I've had two in a variety of locations without any problem at all, even streaming movies. Equally AE are bullet proof and if you check out the Stereophile site you'll see a test which finds them bit perfect and as good as the best CD transport. As I already said I think it's that particular AE having trouble locking onto the clock of the 840CD and this can happen from time to time if the two clocks are at the opposite of the acceptable window. I think this is not a quality issue but a slight mismatch between two devices.


We help lots of people with wireless issues because it's the most popular way of getting music around the house without wires and drilling holes. The two best and most reliable systems are Sonos and Apple and they are both miles better than the Sqeezebox which I've had here and had trouble with. I don't think the problem you have is a wireless issue because if it was, you'd just get stoppages, gaps in the music, but no funny noises. I'd guess that if an Apple TV is lost from the devices list it's most likely the router. Use and Airport Extreme Base station as they seem to have a much greater range.


Having said all that, if the AE is having the stoppages it's just possible the 840C is making a noise as it locks on again.


I've got two Dells and an iMac at work with an AE Base stations and AEs on the test bays and the iMac never has issues.

At home I have AE, ATV, a Mini, a Macbook Pro and an Acer Aspire One with OSX in it and a Dell they all work flawlessly except the Dells.


I hope this helps




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Thanks Ash.


You state that there could be a clock mismatch. What should I do to resolve this mismatch? Buy another dac? Any recommendations under £1000. Or could I used the USB output from the airport express and run it into a USB to toslink convertor that you can buy? I have an Airport Extreme Time Capsule by the way on which I already store my music. Or should I buy the Apple TV again and hope that it works? Do you know about the PS Audio Digital Lens. Sorry for all my questions. Thanks




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The Cambridge Audio 840 is amongst the best sounding made, so I wouldn't start spending money on something else that's not necessarily as good.


If I understand you this problems occurs as Music starts to stream and it clears after a few seconds. If that's correct I suspect it is because the AE stops its stream when there's no music and starts again and this is what's annoying the CA CD. It needs a few secs to lock on. If that's the case I'd stick with what you have because it's good stuff. Better to spend money elsewhere.


The USB from the AE is for a printer only. You could just listen to the analogue from the AE to see if it's streaming okay and you may find it hums when there is no music and you could try another optical cable, but they usually either work or don't.


It's very hard to diagnose by remote control, so you'll have to say if I've got it wrong.




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My friend who borrowed my AE had a similar problem, and he has again now with a new WiFi N one, which has been tried with both analogue and digital outputs. A random distortion noise is heard but we couldn't figure out why and put it down to some networking issue - perhaps interference.


I also suggestion he tried an older version of iTunes as I streaming has changed from TCP to UDP on newer versions, but I haven't been told if this fixed the problem of not.


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Actually normally the music starts to stream fine and sometimes it is not until midway through the song that the screech or distortion of the music happens. Remember if I plug my laptop direct to the dac all is fine. Best Ben



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Actually normally the music starts to stream fine and sometimes it is not until midway through the song that the screech or distortion of the music happens. Remember if I plug my laptop direct to the dac all is fine. Best Ben



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  • 3 months later...

Our engineers and those at Anagram Technologies (the people that help make the CS 840C) have identified a 'quirk' with the optical output of the Airport Express.


Basically, the Airport does not output a smooth SPDIF clocking. Every now and then, the Airport will sporadically adjust its output clock to track the desired sampling rate.

These adjustments are very sudden and are the cause of the noises and/or drop-outs described.


This is not something which could have been foreseen as it is an apparent 'quirk' of the optical output from the Airport Express and not due to the 840C. Our engineers have however, developed an update which mitigates the effects of this irregularity.


If you contact our distributor they will be able to arrange for your CD player to have the appropriate update carried out. This will need to be done by an engineer.


They are contactable on the details below;


Audio Plus Services

156 Lawrence Paquette Industrial Drive

Champlain, NY, 12919

Web: www.audioplusservices.com

Email: [email protected]

Telephone: 800-663-9352

Fax: 866-656-0686


They also sent me the firwware upgrade and I did it myself and everything is now working just fine. Good Luck.


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Do you get the same problems if you have music files on the laptop rather than on the Time Capsule?


Is the MacBook connected via cable or via wireless?






...in my opinion / experience...

While I agree "Everything may matter" working out what actually affects the sound is a trickier thing.

And I agree "Trust your ears" but equally don't allow them to fool you - trust them with a bit of skepticism.

keep your mind open... But mind your brain doesn't fall out.

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Benjamin, if you are still following the thread. I also use an AE and 840C and......


1. Yes the screeching does come from itunes8. Change to 7 and the screeching will stop.

2. The 840C will be totally oblivious to any reclocking device. It re-clocks already in a way that completely discards the timing signal in the spdif stream so don't waste your time on this option.


- John.





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