Film-Tech Forum ARCHIVE: AES cables

This is topic AES cables in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.

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Posted by Brendan Penny (Member # 5041) on 11-04-2009, 05:03 PM:

Does anyone have a good source for long pre-made 25 D-sub AES cables? Alternatively, if I was to build myself, what cable options do I have?

Need to do some runs from projector pedestal to existing audio rack. Approx 10 to 15m runs reqd

Posted by Kevin Fairchild (Member # 4985) on 11-04-2009, 07:06 PM:

www.monoprice.com search for db25.

I get all my cables for our digital equipment there. Some people may call this a no-no, but I have never had a problem with any of their cables. They are inexpensive as well. You can get a 100 foot cable for $14US. Go nuts.

Posted by Steve Guttag (Member # 268) on 11-04-2009, 09:19 PM:

I did a search on DB25 and didn't turn up any AES cables.

But anyway...have always made our own. It is certainly doable.

We use Belden 1803F (4-pair AES snake)...aka "Barney Cable" after its purple jacket.

We use AMP brand Dsubs, crimps...etc...never a problem. However, if you are going to just make one or two...get out the soldering iron and do it the hard way...they will work just as good.

However, you must use AES cable for the longer runs or you will be sorry...it is the only way you are going to maintain the 110-Ohm impedance. I've even seen a DCinema server company supply ordinary audio snake cable instead of the AES stuff...didn't work reliably either. When I got to the theatre...they couldn't figure it out (why it would only sometimes work)....I made and installed the correct cable and whola, no more problems.

Anyway...Belden 1803F comes in 500 and 1000-foot rolls. Some suppliers may sell you "cut lengths" and there are other cable manufactures that you might find easier to source...just make sure it is real AES cable with a 110-Ohm impedance. It should feel and look fatter than normal audio cable of the same gauge.

Steve

Posted by Kevin Fairchild (Member # 4985) on 11-05-2009, 02:18 AM:

[Confused]

Don't ask me how I happened to skip over the AES part of your post... even when it was the topic header. So forget my earlier reply. [Smile]

Posted by Chase Taylor (Member # 778) on 11-05-2009, 10:22 AM:

I did a test on a monoprice cable for the aes output for digital cinema since the cables are so cheap. The cable is 25 ft long and has been in line for 1 year now without a dropout. I certainly understand what Steve is saying and can't disagree with him, but with what I have experienced with the monoprice db25 cable for the price and ease of use you can't knock it to much.

Chase

Posted by Demetris Thoupis (Member # 833) on 11-05-2009, 01:13 PM:

It's the same thing with Dataport and Processor Out Monitor In link cables. For example Dataport cable is not VGA as most people thing as the shielded pairs are not like the VGA in pins 1,2,3 (hot) and 6,7,8 (shield) but in a different combination. Also a PC store will gladdly sell a 25pin Male to Female cable used for Parallel connection and it can easily be used for transfering audio from Processor to Monitor e.t.c BUT its not the correct cable. It does not have the correct impedance and it does not have shielded pairs at it should. The same goes for AES. Just order them from Dolby.
Demetris

Posted by Brendan Penny (Member # 5041) on 11-05-2009, 08:48 PM:

Thanks for those suggestions. Think we will just order a big drum of 'Barney cable' and do it ourselves just to be on the safe side!!

Posted by Pete Naples (Member # 761) on 11-07-2009, 04:53 AM:

That's what we do. For us, as we mainly don't work in multiplex buildings, it is often the case that the server and processor are not in the same rack, so a drum of cable is a must.

Posted by Stephen Furley (Member # 1277) on 12-23-2009, 03:59 AM:

quote: Steve Guttag
I did a search on DB25 and didn't turn up any AES cables.

The use of these cables and connectors for multiple AES streams seems to be quite common; I've seen them used in other applications than digital cinema, but is it actually part of the AES3 spec? If not, are the pin connections standardised, or do different equipment manufacturers each go their own way on this?

Posted by Steve Guttag (Member # 268) on 12-23-2009, 09:16 AM:

The DB25 version of the AES audio is a DCinema thing. The offical connector for AES3 remains the "XLR" style. The DB25 connector is popular for its size and availability (cheap, satisfies CE, 16-channels of AES audio can be used with it). It also easily converts to ribbon cables...and on and on and on.

It is like the 6-channel analog cable on the DB25 (unbalanced)...its "pin-out" was derived due to how the CP200's audio laid out on the JM11/JM21 connectors and no other reason. The CP200 used 2x10 header connector with ribbons...when those same cables have a DB25 squeezed on to the ribbon, whola, you get Pin-1=E, Pin-2 = "Q" or Right-Surround...etc. And that is how Cinema got that pinout that shows up on every "6-channel" input expecting unbalanced 300mV (again the CP200) audio.

The Balanced DB25 pinout for cinema came from the folks at THX. Their original booth monitor the 3417 started that pinout and companies like Sony followed suit and even Dolby got on board with it on the CP650...again, the "standard was formed."

Steve

Posted by Stephen Furley (Member # 1277) on 12-23-2009, 03:49 PM:

Steve,

I did a search for the cable you recommended:

web page

It's quite expensive; not too bad for 4-pair, but look at the price, size and weight for 32-pair. Using lots of wires to transmit multiple digital signals of relatively low bandwidth seems like a rather makeshift way of doing things. Why didn't the AES produce a standard for transmitting multi-channel sound? Let's start with the AES3id standard; I'm not sure how much bandwidth 75 Ohm co-ax can handle, but I do know it can cope with HD-SDI with 16 channels - 8 pairs - of embedded audio, and I also know it can handle 3G-SDI, though I'm not sure about embedded audio with that. If we are talking about audio only then it's clearly going to be able to handle many channels, on one thin, cheap, lightweight, flexible, easy to handle and terminate cable. If you need a longer distance than you can do with co-ax then you could send the whole thing down a single fibre, tens of km of it if you want to. A multi-channel version of AES3id seems like an obvious next step; using these thick multi-pair cables seems to be doing things the hard way. Am I missing something?

Posted by Tony Bandiera Jr (Member # 2365) on 12-23-2009, 05:19 PM:

Contact Bevan at Moving Images Technology 714-751-7998 they can build you any cable, any length and their prices are very good. Tell him Tony sent you. [Smile]

Posted by Steve Guttag (Member # 268) on 12-23-2009, 05:39 PM:

Hey, you are talking to the HDSDI poster child here. I mean picture and sound on an easy to make/buy cable? What isn't to like? I only wish HDMI and DVI had gone that route!!!! What a pain in the ass they are!

As for the cable, our pricing is a bit better than what you are experiencing and we also make cables (and have even done so for manufacturers like MIT). We are not in the raw cable business (but have been known to sell it by the foot) but do make finished assemblies of some cables...certainly Dolby Digital (film) cables, AES audio (coax or twisted pair) as well as multi-channel analog as we stock 6, 8 and 12 channel snake cable too. We also do Cat5 stuff but that generally is going to be cheaper (pre-fab) at other places. We do stock Skew-Free cable for doing "Cat5" like cables for A/V purposes (won't work for data).

Steve

Posted by Brendan Penny (Member # 5041) on 12-23-2009, 06:46 PM:

We ended up just making our own after everyone's advice. Wasn't too much of a pain in the end. Running cable through duct work without 25pin d sub heads on was actually a blessing in disguise!

I would recommend heat shrinking on each connection to be on the safe side though.

Posted by Dan Herron (Member # 5210) on 04-02-2010, 05:45 AM:

What model Amp connectors do you use? Also what pins and tooling? I will need to rewire or replace some cables for 7.1.

Posted by System Notices (Member # 2357) on 11-25-2017, 05:32 AM:

It has been 2793 days since the last post.

Posted by Juan Jose Garcia Calvo (Member # 1702) on 11-25-2017, 05:32 AM:

About the 110Ohms AES required cable impedance...
What about the DOREMI servers getting out the AES out through an RJ45 and using CAT cables?

We are using this to send the 4 AES channels to a Dolby DMA8Plus without problems (using a supplied RJ45 to DB25 adapter) . Are we lucky maybe?

Posted by Steve Guttag (Member # 268) on 11-25-2017, 06:26 AM:

A fortunate characteristics of CAT5e cable is its intrinsic impedance is about 100 ohms, which is in the range of AES.

Note, if AES3 audio is on the cable, the cable should be shielded. It is a noisey signal.

Posted by Dave Macaulay (Member # 813) on 11-25-2017, 07:33 AM:

Shielded to keep noisy signal in and avoid interference to other signals, or to protect signal from external interference?

Posted by Leo Enticknap (Member # 534) on 11-25-2017, 08:36 AM:

Both, if the audio wires are running alongside others (which they usually are).

We use cat6 shielded, with RJ45 to DB25 adapters or an Odyssey board, depending on the application, at either end that doesn't have RJ45 jacks. This has the added advantage that if the audio processor or audio source (media block, IMB or IMS) is changed for something with a different jack configuration later on, you would only need to replace or remove the converter - no reterminating the cables needed.

Posted by Steve Guttag (Member # 268) on 11-25-2017, 06:44 PM:

Nah, I make my own cables of the right type and ends. A very high percentage of our installations are Surround 7.1 and that normally means getting pair 6 grouped over to pairs 1-3. I can generally make the ends cheaper than an Odyssey board. It all depends on the installation and what I want to do and what equipment is involved as to whether I budget in the Odyssey board(s).

I've found zero reason to fool with CAT6 for AES cable. It is thicker, costs more, harder to work with, takes longer to terminate (increasing its cost). I tend to use CAT6 for the "Media" network and that is about it.

Posted by Ken Lackner (Member # 1002) on 12-01-2017, 08:45 AM:

quote: Steve Guttag
I've found zero reason to fool with CAT6 for AES cable. It is thicker, costs more, harder to work with, takes longer to terminate (increasing its cost). I tend to use CAT6 for the "Media" network and that is about it.

Do you mean vs. Cat5, or vs. the purple cable? I assume you mean vs. Cat 5, because Cat6 certainly isn't thicker or harder to work with than the purple cable! Just wanted to clarify.

Posted by Steve Guttag (Member # 268) on 12-01-2017, 09:10 AM:

Than CAT5E.

Proper AES cable is best in terms of signal transmission and shielding (all pairs are shielded and there is an overall shield) but CAT5e cable is "close enough" in impedance that we have not had issues with signal transmission in typical cinema applications.

I'd say we use CAT5e over Belden AES cable about 9:1, perhaps closer to 50:1 now. There are times with AES snake cable works out better for the installation (being able to break the pairs out to different locations and what not or for the better shielding). Honestly though, we've made so many DB terminations that working with AES cable isn't a biggie either.

Posted by Harold Hallikainen (Member # 5405) on 12-02-2017, 03:03 PM:

Note that EBU Tech. 3250-E - Third edition from 2004 states in Appendix 2:

AES/EBU signals on Structured Wiring

There is an increasing use of structured wiring for carrying AES3 signals. Notwithstanding clause 6.1, the practice has been shown to be viable on Category 5 unscreened pairs, meeting EMI requirements, and offering transmission up to 400 metres overall unequalised, or 800 metres equalised, at 48 kHz frame rate.

For a satisfactory outcome, this practice should only be used where the whole length of the connection uses Category 5 UTP (Unscreened Twisted Pair) cable, including that which is installed and any flexible leads (equipment cords), and that the connection is unscreened for the whole length. Alternatively, the whole length of the connection should use Category 5 STP (Screened Twisted Pair), and the connection should be screened for the whole length.

Care should be taken in design of the interface to provide adequate balance on the twisted pair within the Cat.5
cable.

Using RJ45 connectors, conventionally wired, current practice favours the use of pins 4 and 5 for AES/EBU signals (separating them from ATM signals on the same cable). Pins 3 and 6 are the preferred second pair. Note that, for full protection, the interface may have to withstand power voltages specified to support network equipment, and the use of transformers and blocking capacitors on the AES/EBU interface is strongly recommended.

Suggested practice: while the interface is by definition insensitive to polarity, for the purposes of constructing
adaptors, XLR Pin 2 should be connected to RJ45 Pin 5 (or other odd-numbered pin), XLR Pin 3 should be connected to RJ45 Pin 4 (or even-numbered pin).

================

We have run tests with four AES/EBU pairs in CAT5 unshielded cable with a length of 1,000 feet (less than the 400 meters specified above) with no issue. In addition, we have found Ethernet magnetics suitable for AES/EBU. This works well since Ethernet magnetics are more common and less expensive than transformers designed for AES/EBU. Also, you can get RJ45 and dual RJ45 connectors with internal magnetics saving on cost and board space.

Harold