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OK, I'm going to be a troublemaker here and I apologize in advance.

 

I've worked with digital and analog RF datalinks in "non-permissive" and intentionally jammed environments in the military for a long time.

 

My experience is that digital signals, in the same medium, travel with much more fidelity than analog signals.  To put it another way, analog signals are much easier to jam and disrupt than digital.  Much easier.  I've been on both ends of that equation, both as the jammer and the jamm-ee if you will, and digital signals are much more robust, at least in the RF world.

 

So, I do not understand why a cable that I would find acceptable for hi fidelity analog signal transmission would not be suitable for digital transmission.

 

Your comments are welcome.

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Hi BucF16...

 

Here's my understanding of it (and why I always elect to use cabling of the specified type for the application)...

 

AES/EBU 110ohm cabling would tend to be tested to conform for the impedance quoted.

Typical mic cables can be very variable across their length, with the impedance varying and thus allowing more interjection of noise from outside sources. Additionally, with varying impedance, the digital signal can be disrupted. Bear in mind that a digital signal of the type used for digital audio carries not only the actual audio information but time information which assists in the reconstruction of the audio signal at the far end.

 

Whilst a straight binary digital signal will typically retain fidelity over any cable, certain impedances of cable and cable types have been found (through extensive research) to be best suited to certain types of transmission. In the case of digital audio signals using balanced connections, that impedance is 110ohm. I can't explain the physics of it for you, though if my son were here, he would be able to! (he's at university at present doing a degree in bio-medical engineering and signal transmission and processing is a big part of what they do and one of his recent assigments involved running signal integrity tests over different cable types to determine levels of noise/disruption). Likewise (at least in Europe) 110ohm is recommended for DMX signalling also although DMX signalling is considerably simpler than digital audio.

 

So, whilst a simple digital signal is indeed more likely to retain integrity in any given medium, the complex nature of digital audio (plus what ever else is bundled into the L6Link) is better served by a cable of the specified type.

 

As AES/EBU cable is only fractionally more expensive than standard mic cable, you might even consider running 110ohm shielded twisted pair for all applications in your rig since analogue audio runs perfectly happily in AES cabling. That way you'd have the flexibility of only one set of cabling to carry around, all of which would be interchangeable without issue.

 

As has previously been noted, many many people have success running out standard mic cabling for L6Link without any issue... I just see it as an added risk that, as I wasn't encumbered with an existing inventory that I was reluctant to chuck out, I could remove by assembling my rig using the recommended stuff for each application.

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Thanks for the responses.

 

My original premise hasn't solidly been addressed.  In my opinion and experience, analog signals are actually much more complex than digital signals. ANY degradation of an analog transmission causes degradation of the resulting audio.  Degradation of digital signals must be enough to turn an "off" to an "on" or vice versa, or there will be no degradation at all.

 

An analogy would be digital vs old analog cell phones.  Digital phones need much less energy to transfer greater distances.  Everyone can probably remember battery life and cell range just 10-15 years ago compared to what it is today.  Much of that increase in capability is due to increased fidelity of digital signals in the same environment.

 

I could be wrong, but I thought this was a foundation of most of Lin6's wireless mike and guitar technologies.

 

Arne responded that the sharp edges of digital signals are preserved better, but I'd argue that this is LESS important for digital signals than for analog signals.  Why are the edges of digital signals more important than the much more detailed edges of analog signals?  Begging the question, if the pathway is good enough for hi fidelity analog, why isn't is good enough for hi fidelity digital?

 

I'm not saying that you guys are wrong, only that I have yet to hear a reason that makes sense to my somewhat analytical mind and my experience.

 

So far, using my system, I haven't had any trouble with cables EXCEPT the actual connections.  I've had plenty of trouble finding XLR cables that fit snugly and will stay tight through the rigors of a rock-n-roll bar gig!  But, any XLR that I have in my old bag of cords has seemed to work just as well as any other...as long as it stays connected!

 

I would be interested to hear why 110ohm is particularly good for digital VS analog if someone could put on their geek-hat and explain it using medium sized words. My background is technical but I'm not truly an engineer.

 

So I'm happily awaiting a better argument for buying special cords while playing the role of contrarian.

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It's all about how the cable "loads" the digital sending device.  In the case of L6 link the ideal load is about 110 ohms.  Typical non-AES cables are typically about 40-50 ohm (transmission line impedance ... not resistance).  So when you begin to bog down the sending device you begin to get unstable waveforms.  Now the system can still read them for a while but as you add distance  to that cable then they continue to get worse to the point that they can no longer be read in sufficient numbers for the receiving end to make sense of it.

 

This is not so much about digital or analog but it is more specifically about L6 link and AES/EBU links.  Also, generally  there is no issue sending analog down AES cables. 

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Thanks Db

 

Would it be safe to say that the problem is worse over longer run of total speakers or just a longer run of one cord?

 

For example, 6 L6 speakers with 10 ft of cable between each one, or two speakers with 49 ft of cable between the two?

 

Is the problem compounded by multiple devices of differning types on the link?  For example, 4 monitors, 2 subs, 2 mains   versus just two mains?

 

Thanks in advance.  Not trying to be pedantic, just trying to understand the nature of the Line6 Link.

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  • 3 weeks later...

So that means that if the distance to the stage is more than the recommended 50 feet, it would be possible to splice two cables with an electronic gadget that would rebuild the signal?

Is such a box available in one form or another? I don't think I can afford to use a L2m as a plain junction box  :rolleyes:  

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We frequently play in a venue where 50 feet is enough if we put the cable through the audience. But it would of course be much safer if we could put the cabel along the walls, in which case we would need almost the double. Maybe I will have to sacrifice a L2M anyway ... :ph34r:

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Just wondering why the cable needs routing through the audience. Are you running the M20d from the back of house with a sound engineer and running a multicore to it? If so, have you considered running the M20d on-stage with the band and your sound engineer running sound from an iPad out front?

 

Big problem is that whilst you *might* not have issues running a cable longer than 50' (if you're doing as I suspect) then that longer cable run is the first(?) in the chain and any errors that occur would subsequently affect everything downstream, ie ALL your rig.

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In this specific instance (the original question) - a decent "audio grade" cable only has to have usable frequency response up to say 20 khz, (ok double it for those people who have bionic dog ears installed). 

 

A quick look at the AES spec tells us that the signalling is up to 6 Mhz. This is probably the most important detail..

 

More details:

 

To transmit that high a frequency you need to both match the required impedance (110 ohms vs I think 600 for analog XLR) and you have to control the impedance, ie it can't vary too much from 110 ohms. This helps keep the signal strength along the cable and allows the common mode rejection to work effectively. 

 

Finally, it should likely be twisted pair to avoid magnetic coupling with the surroundings else all your signal turns into radio waves.

 

You can get away with a short run of analog mic cable, but you're risking a digital drop out..

 

Your thoughts about jamming are true, but the difference is you will have a hard time jamming a digital signal in a properly designed digital cable. It would probably be easy to jam a digital signal in an analog audio cable.. 

 

Note this doesn't mean the digital cable has to be expensive! (Say no to Monster anything!!)  Consider a cheap cat5e ethernet cable is good for up to 100 Mhz digital. (but not very mechanically sound)..

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  • 7 months later...

so what happens to the sound when you dont use the digital cable??  does the speaker just quit working?  i have two brand new mic cables that are pretty nice but are not digital.  (the guy at the music store hadnt even heard of a digital mic/ xlr cable).  does this mean that in the middle of a show everything will just quit working or what?

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If the data stream is interrupted, the speaker can either "skip" a few seconds or stop working altogether till you reboot it or the mixer.

 

There's no such thing as a "digital mic cable." What you need are AES/EBU cables, which are designed specifically for digital audio streams. There is a difference.

 

Here's an example: http://www.sweetwater.com/store/detail/EBU030

 

DMX lighting cables are basically the same as AES/EBU, since they also transfer digital data.

 

Remember that the maximum length of each cable recommended by Line6 is 50 feet (15 meters).

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Slightly embarrassing that I have not thought of that solution. Think we'll give it a try...

 

For what it's worth, they make a $50 plastic shell cover that you can place over the M20d in scenarios like this, where you are controlling it from a distance via iPad. Sort of like a beer shield / dust cover..

 

http://line6.com/store/item/323/

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What you need are AES/EBU cables, which are designed specifically for digital audio streams. There is a difference.

 

 

 

Yes to what Rick said! I use these by BestTronics, good price, high quality Belden cable.

A 50' length would cost you $45 plus shipping. 

 

http://btpa.com/AES-EBU/

 

Male to Female 3 Pin XLR AES/EBU Digital Cable using Belden 1800F Cabl

All AES/EBU series cables are quality made and tested in the U.S.A.with 110 Ohm Impedence AES/EBU Digital Audio Cable

  • Highly Flexible Black PVC Jacket
  • Hand Soldered with Neutrik or Switchcraft Connectors
  • Quality Made & Tested in the U.S.A.
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And a second seconder...

 

All mine are Sommer AES/EBU with Neutrik gold plated xlr's that I hand soldered myself.

http://www.thomann.de/gb/sommer_cable_binary_234_aesebu_mkii_gr.htm

 

Cost wise, an AES/EBU cable per meter is only around 20% more than a good quality mic cable and if you are capable of soldering, it's easiest and cheapest to make your own up.

UK cost wise, a 10m (33 feet) AES cable using the above sommer cable is around £20 to self build, (about $35) and about £27 ($43) for 15m (50')

 

Perhaps best note is that an AES/EBU XLRF to XLRM CAN be used as a mic cable without any issues.

I bought 50m of sommer and made up the following lengths:

1 x 10m (~33ft)

6 x 5m (~16.5ft)

4 x 2.5m (~8ft)

 

I have 2x L3s, 2x L3m and 2x L2m plus the M20d and the above cables have yet to be insufficient for a venue we've played or a gig where I've done hire of my system for another band. Moreover I have had zero issues with speakers dropping in/out.

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Perhaps best note is that an AES/EBU XLRF to XLRM CAN be used as a mic cable without any issues.

This is true; 110-ohm AES/EBU cable will be fine for a microphone signal.

 

But it's best to avoid using the same cable for both purposes at different times. Mic cables tend to get stepped on, which eventually compromises the integrity of the cable. It's likely that the cable would become unreliable for digital data long before it fails with a microphone signal. To avoid interchanging them, buy different color raw cable or mark the connectors for the intended use.

 

Just good practice.

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in regards to running the M20d on stage running wifi to FoH, that can sometimes be annoying depending on the quality of the wifi signal in the room; i've had some rooms where the 'noise' is so bad i can't go more than 20 feet without the iPad dropping constantly, though a good workaround is running a cat5e/cat6 cable to a wifi router to the FoH area; that should eliminate that issue.

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  • 1 year later...

@BucF16,

      I see this is an older thread, but I wanted to respond to you as an Electronics Engineer with over 30 years of design and test experience in every major area of electronic signaling.  Your original assertion is simply wrong.  " analog signals are actually much more complex than digital signals"  they are no more or less complex, they are simply different and each has its own requirements to optimally carry information (in this case sound information).  

 

I say this not to put you down in any way.  Your experience in analog degradation vs digital degradation is real and correct, but what you are missing is the underlying  mechanisms of each.  What you are see with analog sound is signal amplification and in digital data stream is signal regeneration.  

 

In the first case the original signal and any noise collected along the way is simply amplified (made bigger) when it gets to the destination by the destination amplifier.  In the second case the original signal is detected (picked out) from any noise collected along the way and re-created (regenerated) as it appeared at the source, the noise collected along the way is simply discarded.

 

That is why digital signal seems to just work and then suddenly stop working instead of degrading gradually like analog signal.  It has to do with the noise collected along the way getting so large it simply degrades the original digital information to where it can no longer be regenerated.  There is a very narrow band where the noise is just high enough in a digital system and some parts of the original signal can be recreated and some parts cannot.  We hear that as stuttering or broken up audio.

 

To answer your question about cables.  The AES/EBU cable is built in a way to give a digital signal the best chance of going the farthest distance without collecting so much noise along the way as to cause the digital signal fail reconstruction.  A standard mic cable is built differently and will not carry the signal as far.  That is part of what some folks are talking about with the 110 Ohm impedance comments.

 

So IF you mic cable works on L6 Link without an issue, keep using it!  But if you find the sound experiencing digital breakup or there are L6 link controls failing then go to the real AES/EBU cable.

 

FYI the Hosa AES/EBU cables at Sweetwater are reasonably priced.  http://www.sweetwater.com/store/detail/EBU025

 

Enjoy life!   B)

 

 

Thanks for the responses.

 

My original premise hasn't solidly been addressed.  In my opinion and experience, analog signals are actually much more complex than digital signals. ANY degradation of an analog transmission causes degradation of the resulting audio.  Degradation of digital signals must be enough to turn an "off" to an "on" or vice versa, or there will be no degradation at all.

 

An analogy would be digital vs old analog cell phones.  Digital phones need much less energy to transfer greater distances.  Everyone can probably remember battery life and cell range just 10-15 years ago compared to what it is today.  Much of that increase in capability is due to increased fidelity of digital signals in the same environment.

 

I could be wrong, but I thought this was a foundation of most of Lin6's wireless mike and guitar technologies.

 

Arne responded that the sharp edges of digital signals are preserved better, but I'd argue that this is LESS important for digital signals than for analog signals.  Why are the edges of digital signals more important than the much more detailed edges of analog signals?  Begging the question, if the pathway is good enough for hi fidelity analog, why isn't is good enough for hi fidelity digital?

 

I'm not saying that you guys are wrong, only that I have yet to hear a reason that makes sense to my somewhat analytical mind and my experience.

 

So far, using my system, I haven't had any trouble with cables EXCEPT the actual connections.  I've had plenty of trouble finding XLR cables that fit snugly and will stay tight through the rigors of a rock-n-roll bar gig!  But, any XLR that I have in my old bag of cords has seemed to work just as well as any other...as long as it stays connected!

 

I would be interested to hear why 110ohm is particularly good for digital VS analog if someone could put on their geek-hat and explain it using medium sized words. My background is technical but I'm not truly an engineer.

 

So I'm happily awaiting a better argument for buying special cords while playing the role of contrarian.

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@dboomer,

      Actually such things DO exist, but they are not cheap.  They are called digital repeaters, digital re-clockers, and digital distribution amps (each is different, but all of them can help with the problem of driving digital signal over extended cable lengths.  Just search "AES/EBU distribution" Google Shopping to see a number of different ones.

 

 

@kjellarne,

AES/EBU spec cables should be good over 100 meters.  The specification says 150m, so just by a longer cable!   https://tech.ebu.ch/docs/other/aes-ebu-eg.pdf

 

Please note  Three 50m cables strung together are not the same as a single 150m cable. Each connector adds "discontinuity and mismatch" which degrades the digital signal, so make each single cable as long as possible and use the fewest connectors along the way.  http://www.sweetwater.com/store/detail/EBU100

 

Enjoy LIfe!    B)

 

 

So that means that if the distance to the stage is more than the recommended 50 feet, it would be possible to splice two cables with an electronic gadget that would rebuild the signal?

Is such a box available in one form or another? I don't think I can afford to use a L2m as a plain junction box  :rolleyes:  

 

 

Unfortunately such a device does not exist.

How far do you need to run?

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