Thanks.

I found a site where someone tested the HOSA ODL312 and found that it did a 1:1 reproduction faithfully here: http://www.gearslutz.com/board/so-much- … ality.html

The RME ADI-4 DD might be overkill for my needs. I just need to connect one AES XLR device.

I'm not a cable maker, so I will have to skip attempting to construct one myself.  Also, I'm really not sure if a balanced digital XLR cable works with a coaxial SPDIF connection?  I would think not.

Wow -- thanks.  I visited the Redco site and it looks pretty straight forward to have a custom cable built.  They are also very inexpensive.

Also, I found the details in the FF 800 manual for the cable connections with AES/EBU to SPDIF (on page 28).

So at the Redco site on the custom cable page, I selected:

Pick Cable Type:  AES/EBU
Pick Cable:  W3080 Mogami 110ohm AES
Input Cable Length (feet): 4
Pick Side A Connector Type:  XLR Straight
Pick Side A Connector:  NC3FXX-B 3 Pin Female  XLR Blk/Gold
Pick Side B Connector Type:  RCA
Pick Side B Connector:  F09 Canare Male RCA-Gold

Special instructions: 
XLR pin 1 connects to cable shield only and is not connected at to the RCA connector end
XLR pin 2 connects to RCA tip
XLR pin 3 connects to RCA ring

I guess this is all correct and would do the trick?

The total for this custom cable comes to $15.90 USD.

There's a variety of cable and connector options that changes the price.  The most expensive of all the options comes to under $20.

Whether or not a signal is balanced has nothing to do with whether the chassis ground is connected to Pin 1 - it is determined by the signals/voltages present at the XLR's Pins 2 and 3.

S/PDIF is unbalanced to begin with - there are only two contacts on an RCA connector - signal and shield/ground.   If you are routing a digital signal OUT of your Fireface to some external piece of gear, then there is no way to create a balanced signal without the use of a balancing transformer or similar circuit.  However, the folks at RME thought of this, and designed the Fireface so that all you need to worry about is whether or not the external gear is expecting to see a higher level of signal voltage for an AES/EBU connection (in which case use the Fireface Settings to send the "Professional" level), or a lower one, which is the normal S/PDIF signal strength - the so-called "Consumer" digital connection. 

Essentially, you don't need to worry about creating a balanced signal out of your Fireface's digital output.  The signal being sent is, after all, digital information, so the actual signal is - at any given instant in time - either a higher level of voltage, or a lower - this ain't Hi-Fi.  As long as the receiving equipment can distinguish the difference properly, then your digital transmission will succeed.

You don't have to worry either, if you are routing signal FROM an external piece of gear which has an AES/EBU digital connection, IN to your Fireface.  The digital signal exists in an unbalanced form as the voltage differences between the XLR's Pin 1 and Pin 2, so really all you'd need to do is connect these two to the Sleeve and the Tip of your RCA connector respectively, and you'd be good to go.  Those smart folks at RME designed the Fireface's digital input to be capable of receiving a variety of incoming signal voltages, so you don't need to worry about overloading the digital input with an incoming AES/EBU signal.

I think you're a little fuzzy on just what a Balanced connection really is.  What makes it "balanced", is that circuitry in the source equipment will take the signal to be send via Pin 2, splits it off and inverts it in polarity and sends that to Pin 3 - so that the signals present at Pins 2 and 3 are 180 degrees out of phase with each other - they're mirror images of each other through time.  The signal travels through the wire - often some distance - and the wire can act as an antenna to pick up electronic noise interference.  The noise component of the signal arriving at the receiving end will be in phase on both the Pin 2 and Pin 3 connections, so when the receiving equipment takes the Pin 3 signal and inverts its polarity, then combines the result with the Pin 2 signal, the noise will be effectively canceled out - pretty neat, huh?

If you wish to create an unbalanced signal from a balanced one, without a lot of fuss, you can simply connect the Pin 2 signal to the RCA tip and Pin 3 to the RCA Sleeve, which will effectively double your signal strength - and disregard the Ground/Shield connection altogether.  Now, instead of the RCA Sleeve being a stable unvarying ground voltage level, it becomes the mirror image of the Tip signal, so the voltage potential between the two will swing twice as much as the condition that exists when you have Pin 2 > Tip and Shield/chassis ground > Sleeve.  The higher signal voltage swings are probably enough to overcome the influence of any noise picked up along the wire- again, we're not talkin' Hi-Fi here.  Happily, the RME designers were thinking about this as well, and created the Fireface's digital input stages to be able to accept the voltage levels coming in from an AES/EBU source without any damage.

The actual code streams sent by AES/EBU or S/PDIF sources are, for all intents and purposes, identical (there are some differences in the header of each digital "word", but these are easily ignored, and the actual audio data streams are identical).

Whether or not you choose to wire Pin 3 to the RCA's Sleeve, or Pin 1/Shield to the RCA's sleeve - I don't think it makes much difference for short cable runs.  I have used a 3 meter RCA to RCA wire with a stock RCA to XLR male and an RCA to XLR female to create an effects loop with my Lexicon Nuverb reverberator, which has only AES/EBU for input and output.  This works just fine as long as I have the "Professional" Digital connection setting made in the Fireface's Settings.

Digital and analog connections don't interfere with each other. Neither do individual analog connections.

Connecting AES/EBU gear to SPDIF I/Os is indeed not an issue with suitable cable adapters.

Regards
Daniel Fuchs
RME

The key thing to note here is that the RME SPDIF in and outs are transformer isolated.  This means that it does not matter whether they are connected to an unbalanced path (such as coax cable with one side grounded), or a balanced pair (neither wire connected to ground).   In fact the output is more accurately called 'floating'.  (Note that the RCA connectors for SPDIF are isolated from the chassis).  This means that if you are connecting SPDIF between two pieces of equipment, there can be no flow of current between the two along the shield of the SPDIF connection to possibly cause a hum loop.

Compatibility between SPDIF and AES is well covered in the RME manuals, in terms of levels and protocol.   However it might be worth mentioning that in this instance the choice of special 110ohm AES cable is unnecessary at least on electrical grounds.  (Mechanical grounds such as robustness and flexibility is another matter.) 

Firstly the nominal impedance of SPDIF is 75 ohm, that of AES is 110 ohm.  But over such a short distance, the difference in impedance is not important, and any old cable (mic cable, coax cable, etc.) is fine.   It is only important over longer distances (10s of metres).  Then  if you are going from SPDIF to AES, you should use a 75 ohm to 110 ohm convertor box (such as made by Neutrik) before connecting to the AES cable.  Matched impedances are important for reducing reflections of the signal pulses which can lead to increased error rates in transmission - but only over longer distances.

Secondly, according to the standard, it also provides for transmitting AES over co-ax cable ie., unbalanced, 75 ohms.   Part of the reason is that coax can have a much lower loss at AES frequencies than 110 pair cable, and therefore the signal can travel greater distances.  Important if you are a broadcaster or in a large venue.

But for most RME users, the patch cable set out in the RME manual is perfect - use a consumer RCA-RCA video cable, cut one end off and terminate it on an XLR connector as per diagram.  My only advice is check carefully that the RCA connector is of suitable quality.  There are some RCA connectors where dimensions are not exact and they do not fit well on the RCAs on the RME (like XLRs, good RCA plugs are not cheap).

Glad to hear!  $15 is MUCH better than $100 :-)

Just a thought. Is there any reason why you need to use the AES output on the mytek? If the SPDIF works great then why not just use that? Is your custom cable passing audio?

Isaac P

I've heard conflicting information about AES vs. SPDIF. I've heard that AES is the "professional" interface, and SPDIF is the "consumer" interface. I've also heard some people say there's no difference, but they always seem to waffle about that a bit.

Also, if there's "no difference" between AES and SPDIF - then why do they both exist?

Since I couldn't get a straight, simple answer about AES vs. SPDIF anywhere, I decided to err on the side of caution and use AES, since it's "professional".

So it would be nice to get some clarification as to whether it makes any difference. I've heard a lot of essay-length answers to this along the lines of "It shouldn't make any difference" or "It's pretty much just as good". What I've *not* heard anyone say is "There is no difference at all in terms of audio".

If that last statement is true, I'd like to know that unequivocally, without a rambling, inconclusive, essay-length lecture on the subject. I don't want to hear about "if you connect the ring 3 to  tip 4 and make sure the sleeve is grounded to your local nuclear power plant, then maybe it'll work, or you could solder ring tip 5 to sleeve 4 and buy a welding machine and weld it into ring tip and sleeve 87, but it probably shouldn't matter, unless the length is over 2.63 meters, then SPDIF is just as good, but not really, because it's the consumer interface, but it's kind of, almost, sort of just as good, especially when you connect ring to the tip 4 to the unbalanced sleeve, but you don't know what unbalanced is, so let me explain that for an hour, and the sleeve is grounded to my grandmother's 120 volt electrical box,  it should be probably somewhere near just as good, I think, but I'm not really sure etc. etc. ad nauseum".

I WANT A CABLE THAT WORKS: THE END.

The cable is passing audio. It's just that it also passes a lot of electrical noise (loud hiss and other noise); this noise gets quieter if I touch my computer (macbook pro), then gets louder again if I stop touching the computer. The electrical noise also gets louder if I go near the electrical outlet, or near my mic preamp, and gets quieter if I touch those components. There is clearly an electrical issue with this cable - not sure if it's because of the instructions on this thread being wrong, or if Redco built the cable wrong. I purchased two of these cables, and both have the same problem.

Since this cable is not at all common, and is not commercially available at all, it would be REAL NICE if RME could set something up with a vendor so people could purchase this cable without going through hell, and wasting days and hours and weeks guessing, troubleshooting, and dicking around with the weird cable that RME for some reason thought would be a good design idea. I'm sure many vendors would be thrilled to get all this business. All RME has to do is point the vendor to the specs in the manual, and they can sell the product labeled specifically as "AES Cable for Fireface 800". Then no one else will have to wonder about this, or waste their time, as I and many others already have. Message to RME: Not everyone on earth is an electrician, or knows how to solder, or wants to know how to solder. As a guitarist, I'm a musician, not an electrician. I play an instrument, and I buy the cables for it at the store, and that works real well for me and millions of other people. Find a vendor, and make this cable available, and stop presuming that everyone knows how to solder, or even wants to know how to solder.

Or gee, maybe they could INCLUDE A FREE CABLE WITH THE $1700 FIREFACE???? I mean, I got a free pick with my Gibson Les Paul.

hi,

I actually already asked the same questions that you are asking: please read my post. i would like to know if the instructions for the cable wiring, as i quoted in my first post, are correct. If the instructions are correct, then the problem is with the cable. If the instructions are not correct, then the problem is with the instructions.

You basically just re-asked the same questions I already asked, so your post is not very helpful at all... and actually kind of irritating.

I did read the owner's manual. I did read the page that you cited. However, I gave the exact instructions and specs, that you posted, to Redco, and the two cables that I got back don't work properly. So re-reading the manual is not going to help.

The one question I would like to know from RME is: Are the specs that Jamil posted correct? If they're correct, then the cable was not made properly (or perhaps there's a problem with the Fireface). If they're not correct, then the problem is with the instructions.

Or another thing that I think RME should do: Post a link to where a person can buy this cable, manufactured the way it should be, without going through hour-long lectures and guesswork about it.

BTW, I don't find the manual for the Fireface 800 to be very well written at all. The information is disorganized, and goes from one subject to another, then 20 pages later back to the same subject again, with no rhyme or reason, and no real organization at the meta-level, other than dividing into Mac  and Windows.

RME should hire an experienced Technical Writer, and re-write the manual, organized in a more meaningful and useful way. I hear people saying how good this manual is, it's one of the worst I've ever read. The only worse manual I've ever seen is the one that accompanied Logic when it was owned by the German company Emagic. Thankfully, Apple threw that whole manual in the trash when they bought Emagic, and got some really savvy, intelligent  Technical Writers to completely replace the worthless manuals from Emagic. Most companies underestimate the importance of documentation, and get some in-house hack to make a complete mess of the manuals, with bad formatting, and meaningless rambling organization, thereby confusing and irritating their customers. That's one of the things that separates immensely successful companies like Apple from companies that achieve only moderate success.

The manual for this product should be completely re-organized, preferably by a native-English speaking professional Technical Writer. A pro Tech Writer would have no problem making this a good manual. It probably would only take a few weeks, maybe a month, of work to make it good, and RME would enjoy the benefits of that (e.g., increased customer satisfaction, less time spent on support, and answering stupid questions about weird proprietary cabling) for many years to come. It would be a very small investment to hire a writer for a few weeks; this investment would pay for itself quickly, and many times over. Why can't you be more like Apple, with some real creative energy and attention to detail, instead of just muddling through with the bare minimum quality of documentation? You should do what Apple does - that's why people like them and buy their products so much.

And maybe the new manual could include a URL to a vendor that sells this damn weird cable.

That's the thing: if one of the cables was bad, I could chalk it up to a mistake. But both are bad, which makes me suspect the instructions. But you say those instructions worked for you, so....

I think RME could do a lot to reduce the ambiguity by working with a vendor to sell specifically this cable. Everyone who needs this cable has to waste a lot of time, post in forums to get semi-reliable info, and guess if the product is correct. There's no need for any of this: RME should post a link to someone who sells this, or maybe they themselves should sell it. (or maybe just include a normal AES input on the freaking box????)

Can I trade in my Fireface 800 for one?

Also it's possible that the aes on the mytek is chassis grounded strangely or faulty. I've been using the spdif on my multiface with normal spdif and aes for years without dramas.

As a sidenote I find the RME manuals very good and easy to read. (I am a native english speaker)

Isaac P

Thanks for that answer. I do appreciate it. That being said, I do hear conflicting information elsewhere, that SPDIF is more subject to interference, jitter, etc.

I will trust your answer for now though, and hope that my 1 meter spdif cable run will not introduce any hidden interference or jitter.

What exactly would I be measuring for though? What measurement would tell me that this was not wired correctly? Would the Behringer unit posted above (thanks for that) provide the kind of measurements I would need?

Just FYI, this is weeks and hours and days spent screwing around with a cable. And still I have no solution in hand, other than to use SPDIF, which seems slightly less desirable, since the other option (AES) is present and available. 

Is there anyway you could just talk to a vendor, and have them post a link to order exactly this cable, so I don't have to guess whether the cable is the problem or not?