Airport Express/Streaming Audibility Tests

How should jitter appear?

As I understand it, when there is jitter applied to a sinusoidal input, it has the effect of modulating it, creating additional side band components. The side bands are spaced from the input signal by the frequency of the jitter.

 

Simon I think your 840 is faulty.

I have two AEs (old g version and new n version) and both worked with my 840.
They also work with a new DacMagic, MF V-DAC, two DEQs, and my external sound card.

Don't agree with your comments about digitally recapturing analogue.
The method seems to capture the finer differences between TTs so where is the difference?
Also, if I re-capture the output of say, a Dacmagic fed via AE and compare the file directly to a rip, the rip should surely slaughter the analogue capture. This must surely demonstrate if the AE is indeed crap?
There is considerable theoretical bias in favour of the simple rip in that test.

Re the Stereophile test, you might be looking at the analogue output. They say this about digital:

 

Rob, I know that it isn't faulty because it locks onto the optical out at 24/192 from each of the 4 such equipped devices I've tried it with. The only device it has ever had any issue with is the AE.

The Dacmagic uses a different receiver chip to the 840.

It doesn't capture the fine details between turntables at all, Almost everyone who does needle drops accepts it only captures gross differences and broad strokes. Just check the feedback from Andrews last bake-off to read that all present said the drops were not representative of the sound on the day.

What on earth would the point be of trying to compare an original rip with a file that has been ASRC to beyond 192khz and then downsampled back to 44.1? Do you expect a file comparator to show them to be the same?

 

More likely that the specific AE was faulty, I had one that only locked on optically when it was cold, after it had warmed up it dropped out never to relock. It's replacement is fine, no issues at all.

Tony.

 

Vinyl enthusiasts with high end TTs will never admit that a needledrop is fully representative of the sound of the deck in the flesh. Only when confronted with the straight A/B and asked to comment does the door to the hiding place slam firmly shut.
There will of course be instances where the difference is quite obvious, but thats due to bad sound cards and nothing to do with existing digital technology being unable to capture the vinyl source.

Your comment about looking at the file with a comparator unfortunately confirms that most audiophiles cannot or will not trust only their ears. You are suggesting, rightly, that many will have to cheat.
Says it all really!
About time that changed, though it is an uphill struggle for sure.

But to answer your question, yes I do think it possible to do it.
I'm sure i can find something decent that isn't out there for easy download, so without access to the original file that makes cheating much harder.
Doesn't matter if the files appear a little different in a comparator - not if the source file is unknown to the viewer.

 

Very likely.
There must be hundreds of thousands of them in use with all sorts of kit. Not much reporting of problems that I can see.

 

My point about the file comparator is that you want to prove an AE is perfect, the only way to do that is to look at the bits. Or do you think the ear is somehow now infallible?

You are suggesting they will have to cheat, i'm suggesting there's a difference between a file being modified and that modification being necessarily audible in every case. You are ignoring the fact that both the dacmagic and 840 resample everything. If you think this is inaudible then why buy DACs who's entire reason for existence is to improve the sound through resampling?

Have you had a logic bypass or what?

If you want to prove the airport express is inaudible in circuit then you ned to find a way of doing it that adds no other variables, so far you haven't.

 

http://www.pinkfishmedia.net/forum/showthread.php?t=83778&page=14


john Westlake seems to think it has high jitter as well as problems with keeping a broadcast lock.

 

Well I think you are making a lot of assumptions Simon.

I don't have to use a cambridge dac for starters.

I'm proposing that people listen to music that has passed through an AE and compare it to the music that hasn't. See if they can detect any difference.

So what if a file comparator displays some difference?
You presume this will be audible in every case. Perhaps it isn't.

Adding other variables is no problem if they are negative surely?
I can see the objection to measures that might attempt to correct any flaw in the AE digital output - give it a leg-up so to speak but I'm keen to avoid that.
They can only add to the 'crap' factor. I'm thinking here of re-capturing analogue for example. If after that the listeners still deem the AE feed to be indistinguishable from the rip, don't you think that raises a whole bunch of questions?

I've already seen the Westlake euphoria but it doesn't interest me.
I'm sure his products sound great though, just like very many other good dacs.

 

I think the factor Simon doesn't like, is adding other things than the AE to the loop. The best thing to do then, is to do like Tony said (IIRC). Record the analog out of a DAC driven with an accepted good digital source, and do the same driven with the AE. Then the only difference is adding the AE to the chain.

 

Happy to do that.

Plus a straight rip perhaps, so a reference that hasn't been through analogue at all.
This will address other issues such as the additional analogue stage losing detail or nuance.

People don't seem very interested in the topic though.
I see Tony, Paul, you and I only so far.

 

Spot on.

It needs to be a real demo, done live, you can't record it without introducing confounding variables. I'd be happy to hear the digital output through any none ASRC DAC.

I don't presume all differences in data to be audible, far from it. But I would like to know if they are identical...

 

i think people are burned out on downloads.

 

Fair enough.

Do you still regard the AE as crap into a dac that up-samples and re-clocks?
If so, why given your earlier comments.

Assuming it locks and works obviously.

 

Hi Robbo

Maybe it's because it's an Apple choice?

I humbly think apple products look lovely, but wouldnt buy them personally.

Perhaps non-interested folks dont use Apple computers?

Just a thought, maybe interest is higher than I think, I dont know.

 

Might be, but of course AE and iTunes works on PC and I suspect thats where the vast majority are used. Good that I didn't jump the gun and start making up leads and uploading files

Anyway, how are those passive crossovers going?
Did you get the new inductors?

 

lol, mundorf screwed up and sent air cores (but of the right value). expensive air cores mind you - about £40 each.

I am trying to get them to provide the right inductor, I doubt they will want the old ones back - and if so I will still hopefully be able to try both before returning the old ones.

With my new tribute autoformer passive, its really sounding great at the moment.

Quality differences between CD and LP are standing out though (or at least my vinyl front end and CD front end).. so more tweaking, playing, general farting about will follow.

I would like to measure the L-pads where I have them and replace them with decent quality resistors before soldering. I know this will sound better than the carbon tracks of an Lpad.

Lots to play with at the moment.

Have also been taking my 834P to pieces and upgrading it, aka Thorsten's upgrades. Done the signal path, power supply to do soon. I've taken photos as I've gone , and will doubtless put a thread up eventually.

Its all go

Sometimes I think there is beauty in simplicity, and I am enjoying a ''one power amp life'' tremendously.

 

mmm, I own an ipod, an Iphone and my main music source is a shiny Mac book pro. So my disgust with various none working AE is due to them not working, no more no less.

Rob, I've never been able to get an AE to work constantly, ie not chirp and burp and drop out for more than a few minutes when plugged into my 840c so based on that and the fact that no other pc interface has ever given my any hassle, I think it's crap.

I have no idea how it sounds in other circumstances, it could be gods gift. The only other hifi I consider to know well enough to make judgement is YNWANS, and he's analogue only so no chance to test it there.

 

That clarifies things -I thought the comment about it being crap were purely directed at the sonics. If the damned thing won't work then I understand entirely.

Mine have all worked though I did have an issue last year that turned out to be a network problem. I know that it mutes and drops lock between tracks and i've heard that cause issues on some dacs. Some don't seem to lock/unlock cleanly though I think modern ones should.

On the sound quality front, my current view is that it is probably transparent into most modern dacs but I've had niggling doubts sometimes. On a few occasions I've connected the mac optical straight into the dacs and thought it slightly better. Can't be certain though and that's part of the reason for wanting to open this out.

In 2010 - struth!

 

There are three observations I'd like to make here .......

1. It's pretty obvious from the several threads in other places, over some considerable time, that sq's Cambridge 840c CD/DAC is faulty. Cambridge admitted that the original design was problematic and re-engineered it. Also sq's example has been the subject of non-factory modification to 'improve' it's performance. I don't think he will solve his problems till he dumps it.

2. Keith Cooper of Purite Audio is the importer of the Hi-Face and other similar devices which provide an alternative cabled usb s/pdif output to the Mac optical port and wireless Airport Express. One has to question whether his bias against the Apple products is simply so that he can sell more of his own third-party product.

3. Apples Airport Express in any event has now been superceded by the New Apple Tv which has more facilities (inc video) than the Aex and only costs £20 more money (£99 total)

One should not forget that the signal chain is merely digital ethernet and s/pdif, both of which are in huge world wide usage and very well understood, and that the competence of the DAC which is used to provide the analogue feed to the amplifier is all important.

There are many DAC's which are poorly or inadequately designed, but overall the properly implemented designs give truly stunning audio performance not previously available from older technology. This includes several low cost designs, so it is not necessary to throw money into 'audio-phool' products either.

JC.