The No.1 Website for Pro Audio
How important is it to have all WC cables the same length?
Old 31st July 2005
  #1
Lives for gear
How important is it to have all WC cables the same length?

I've got 6 pieces of digital gear clocked from an Aardsync ll / Sync DA combo. They're connected with different length Apogee word clock cables (BNC), ranging from .5 to 3 meters. They're different lengths because I've picked them up on eBay over the last year or two.

After a good song by good players in a good sounding room with good mics (positioned well) into good pres...where does equal length word clock cable rate? Like 10th, or 110th?
Old 31st July 2005
  #2
Lives for gear
 
brianroth's Avatar
 

Probably 110th <g>.

Bri
Old 31st July 2005
  #3
Lives for gear
Ha, thanks Bri, I always appreciate your exp here. That would be my gut guess, I suppose. Hard to imagine that a foot or two could effect, say, clarity or imaging all that much. Maybe a 15 meter difference would, I dunno.

One is never quite sure nowadays, though...

Next I'll be convinced I need high-end ac cables!
Old 31st July 2005
  #4
Lives for gear
 
Doublehelix's Avatar
 

Funny, I have heard that it *is* important, although what do I know, I just bought into the hype and have used all same-length cables, so I have no expertise here at all.
Old 31st July 2005
  #5
Lives for gear
I guess a more tech-oriented guy could do the math and tell you why it's important. In lieu of that, a simple listening test might suffice.
Old 31st July 2005
  #6
Lives for gear
 
zemlin's Avatar
 

Light travels through space at about 186,000 miles per second. I don't know if the speed of light through fiberoptic cable is slower or not. I suspect it is, but I don't think that matters here.

I did a quick and dirty calculation. In order to effect 192KHz sampled audio enough to offset the signal by 1 sample (.005 ms) the cables in question would need a length difference of nearly 1 mile (maybe 1500 meters).

A 1 meter difference will get you a time offset of 0.000000333 seconds.

Are you going to lose sleep over that?
Old 31st July 2005
  #7
Reality rears its seldom seen head.

heh
Old 31st July 2005
  #8
Lives for gear
 

If you're tracking with different A/D converters locked to one clock, the same length cable would be absolute perfection. Then again, if they're not the same length, I doubt anyone could hear it.

I'm using a 5' cable on one digital multitrack and a 25' cable on the machine that it's transferring into. No problems, can't hear the difference in cable lengths at all.
Old 1st August 2005
  #9
Jai guru deva om
 
warhead's Avatar
 

Seems like if you're using a distribution box for WC you would want all of the outgoing cables to be identical in length. In daisy chain it would not matter.

?

War

PS: TheTruffleKing, if you don't own high end AC cables by now then I don't think you're going to make it in this business. After all, they don't know why they sound better, they just do. Not compelling enough?

Old 1st August 2005
  #10
Lives for gear
 
Doublehelix's Avatar
 

Quote:
Originally Posted by zemlin
Light travels through space at about 186,000 miles per second. I don't know if the speed of light through fiberoptic cable is slower or not. I suspect it is, but I don't think that matters here.

I did a quick and dirty calculation. In order to effect 192KHz sampled audio enough to offset the signal by 1 sample (.005 ms) the cables in question would need a length difference of nearly 1 mile (maybe 1500 meters).

A 1 meter difference will get you a time offset of 0.000000333 seconds.

Are you going to lose sleep over that?

Word Clock cable is coax cable, not fiberoptic, but your calculations are still probably pretty close, eh?
Old 1st August 2005
  #11
Lives for gear
Quote:
Originally Posted by warhead
Seems like if you're using a distribution box for WC you would want all of the outgoing cables to be identical in length. In daisy chain it would not matter.
Well, that's my setup, and, like doublehelix, I've heard that in this case you should keep 'em the same length. No one ever tells you why or what horror will befall you if you don't.

I'd ask Dan Lavry, but all I really want is a simple answer. heh

Quote:
Originally Posted by warhead
PS: TheTruffleKing, if you don't own high end AC cables by now then I don't think you're going to make it in this business. After all, they don't know why they sound better, they just do. Not compelling enough?

No, because I also like the sound of money.
Old 1st August 2005
  #12
Lives for gear
 
brianroth's Avatar
 

In "ancient" analog video systems, matching coax cable lengths within a foot or less was important since the different cable delays would slightly shift the phase of the color subcarrier, which is a 3.58 MHz (approx) signal. A shifted subcarrier would cause shifts in the color "tint" when fading from one signal source to another.

However, at 44.1/48 kHz wordclock frequencies, the same differences in cable length would be perhaps 1/100th of an effect.

That being said, there is NO sin in keeping the cable lengths vaguely the same...don't mix 1 foot cables with 100 foot cables!

Bri
Old 2nd August 2005
  #13
Gear Addict
 

Quote:
Originally Posted by TheTruffleKing
Well, that's my setup, and, like doublehelix, I've heard that in this case you should keep 'em the same length. No one ever tells you why or what horror will befall you if you don't.

I'd ask Dan Lavry, but all I really want is a simple answer. heh



No, because I also like the sound of money.

The simple answer is:
All things considered, the best thing to do is always go for the shortest cable you can live with. I would not redesign a whole setup just for ending up with very short cables, but whenever possible, within reason, use a shorter cable.

Following that advice will lower your cable series resistance, reduce cable capacitance, reduce transmission line reflections, reduce rise and fall time degradation including the impact of skin effect, reduce pickup of unwanted signals (AC line, radio signals...), reduce the radiated energy into the environment...

Some of the stated factors are important for speaker cables. Some of the factors mentioned are important for digital transmission. Other factors are important for mics and for audio signals…

There are many times when extra cable length does not hurt performance by any noticeable amount. But I can not think of a single case for audio (both analog and digital) where more length helps matters.

So the safe bet is: when you can use short cable, do so.

Regards
Dan Lavry
www.lavryengineering.com
Old 5th August 2005
  #14
Gear Addict
 

Quote:
Originally Posted by Dan Lavry
The simple answer is:
All things considered, the best thing to do is always go for the shortest cable you can live with....So the safe bet is: when you can use short cable, do so.

Regards
Dan Lavry
www.lavryengineering.com
Let me add a point to what I said in the last post:
No you do not need to keep the cables at equal length.

The signals travel on wires at very fast speeds (more then half the speed of light) and that is true for all electrical signals, be it audio, digital, high power, low power….

A reasonable ballpark estimate for the speed of a signal on a wire - 8 inches for 1 nano second of time, or 1.5 nanosecond per foot. So matching cables to say 10 feet yield only 15 nanosecond time mismatch. This is insignificant for audio and for digital audio.

Regards
Dan Lavry
www.lavryengineering.com
Old 5th August 2005
  #15
Lives for gear
 
zemlin's Avatar
 

Quote:
Originally Posted by Doublehelix
Word Clock cable is coax cable, not fiberoptic, but your calculations are still probably pretty close, eh?
Yeah. I don't know where I got the idea that we were talking fiberoptic. The speed of electric signals through copper is about 2/3 the speed of light - so my point stands - shifted only slightly.

I did a comparison between cables a while back. There was a lot of talk about capacitance and the terrible things it would do to your HF on long runs.

Using Canare starquad mic cable (46 pf/ft), I had a 15 ft cable, and then daisy-chained a bunch to make a 260 ft cable. My learnings from this test made me feel OK about my collection of Canare cables.
https://www.gearslutz.com/board/so-much-gear-so-little-time/27967-cable-length-capacitance-does-matter-test.html
Post Reply

Welcome to the Gearslutz Pro Audio Community!

Registration benefits include:
  • The ability to reply to and create new discussions
  • Access to members-only giveaways & competitions
  • Interact with VIP industry experts in our guest Q&As
  • Access to members-only sub forum discussions
  • Access to members-only Chat Room
  • Get INSTANT ACCESS to the world's best private pro audio Classifieds for only USD $20/year
  • Promote your eBay auctions and Reverb.com listings for free
  • Remove this message!
You need an account to post a reply. Create a username and password below and an account will be created and your post entered.


 
 
Slide to join now Processing…
Thread Tools
Search this Thread
Search this Thread:

Advanced Search
Forum Jump
Forum Jump