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Jitter and 75ohm cable length

I have read a number of papers on how cable length plays a role in Jitter between transport and DAC. After all of the dust settled I arrived at no sound conclusion, on paper, so I decided to use the ears of my 17 year old budding Audiophile to settle this by LISTENING! My transport is a Wadia 171i (WAV/LossLess files)and my DAC is a Cambridge AZURE 840C. I had three cables in my test, my 1M Kimber D-60 illuminations, a 3' HAVE/Canare and a 6' HAVE/Canare. All three cables sounded good, but in the end the victory landed on the 3' HAVE/Canare by a fair margin followed by the Kimber and last the 6'HAVE/Canare. In my readings I came across a number of articles saying you should use at least 1.5M of cable to reduce reflections in the cable so as to not harm the clock signal, yet an RF engineer said this was a bunch of "Bunk" and 1M would be better, in fact he said the shorter the better. So, forgive my verbosity, what are your thoughts and experience in this area? My 3' $25 HAVE/Canare beat up my $390 Kimber, I believe due to proper honest 75ohm terminations vs standard RCA connectors, and as far as length goes, at least in my system, 3' was by far the best. Thanks!
Rpg
rpg

Showing 4 responses by magfan

magfan
1,583 posts
 
Notes on the 840c

First, it has both balanced and unbalanced outputs. The balanced make for quite an improvement. Choice of cable? Gigantic, as you well know. I'm not a big cable experimenter, but the 'as issued' unbalanced went to the trash and I bought some Mogami balanced.

Secondlly, the digital inputs of the CA840c are somewhat MORE prone to jitter effects from the source than many other players / DACs. To that end, CA has issued several Software Revisions, none of which they'll send you anymore, wanting to (either or both) keep people from bricking there players OR drive business back to the dealer. The last revision I had wanted XP and the computer MUST have a serial port and you need a Null-Modem cable.
I was unable to get an Apple AirportExpress to play properly with the toslink input of the player. Simply too much jitter.

I'd recommend looking at the software rev of the player and examining the downstream cabling used, since that won't be a trivial effect.
magfan
1,583 posts
 
CA no longer sends out the file. It was 'zipped' and contained a readme and the installer and some other stuff.
It is on my laptop but I've never mustered the guts to DO it. My laptop is Windows 2000 or ME....dual boot. NOT XP, which is what they recommend.

You have more information than I. If they have only issued one software upgrade, than I've got it. I probably also have the 'old' caps.....

To find out you press some front panel buttons on the player......01/67/1.2 is in my player and found by repeatedly pressing the 'menu' button.
I don't know what the latest version is 'supposed' to be.

And Yes, I think you are on base about the AE jitter issue. The Stereophile test showed it to be awful. The AE is unclocked, as I understand it. I also make sure my computer is doing nothing else when I stream music via iTunes.
magfan
1,583 posts
 
I don't care about any jitter on the analogue out.......It is is jitter on the digital signal which renders the 840c unusable. OR, is the 840c simply sensitive to even that moderate level of jitter....?

From the Stereophile test: This is analogue? not digitial?
"The AirPort Express stumbled when it came to its measured jitter performance—hardly surprising, considering it has to derive its 44.1kHz word clock from an asynchronous, probably encrypted datastream"

Now, with the above stated jitter at 258ps, I'm back to ground zero as to why my 840c doesn't like the dig out of the AE.

other questions....
Would the ATV be any better? (Apple TV). Would the DACMagic be prone to the same problem as the 840?
magfan
1,583 posts
 
Apparently, the AE/840c jitter 'thing' was a known issue. CA issued a software update, which I've got here.......somewhere, but have been too Chicken to install.
It uses a null-modem cable and the requested OS is Windows XP, which my laptop doesn't have. The procedure sounds simple, but than again, were dealing with confusers, here.
I'm sure that CA would be thrilled if I 'bricked' my player. Also, CA no longer sends out the update to individuals, or so I've heard. That COULD be because too many people failed in the update and were really....angry.
I like the AE, even the analogue output. Using my iPod Touch as a remote is just icing on the cake.
You write about jitter induced at the impedance boundry, but what about a simply poorly clocked system? Shouldn't that be added in to the total system jitter? Or perhaps multiplied. if you are sending out a poorly clocked signal into the cabling with the reflections, it sounds like you are compounding the problem.....
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