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  #1  
Old 05-02-2007, 07:42 AM
Dan Tinen Dan Tinen is offline
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Default Converting S/PDIF output to AES input

I need to convert the S/PDIF digital output of a Digidesign 002 to an AES digital format to input into a CraneSong digital monitor control. I know that S/PDIF and AES have essentially similar data streams (with the exception of some subcode data...S/PDIF sends track markers etc. and Serial Copy Managment System, if memory serves); it's just that S/PDIF is a lower voltage unbalanced signal and AES is balanced with a 3 to 10 volt signal.

Questions for the forum:
1. Has anyone used an S/PDIF-to-AES transformer from an 002 to anything else? Where did you get it?
2. Has anyone ever wired an RCA-to-XLR adapter (without a transformer) and had any luck going from S/PDIF to AES?
3. Has anyone used an active format converter of some kind?

Thanks.
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  #2  
Old 05-02-2007, 08:18 AM
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Default Re: Converting S/PDIF output to AES input

This is what you need: PERIOD

http://www.canare.com/index.cfm?obje...5E76E3D1E1CA3D
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  #3  
Old 05-02-2007, 08:57 AM
BRH BRH is offline
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Default Re: Converting S/PDIF output to AES input

i've done it with just a XLR-RCA adapter in a jam and it worked fine, but I'd get the proper Canare transformer. Those look really good.
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  #4  
Old 05-02-2007, 12:03 PM
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Park Seward Park Seward is offline
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Default Re: Converting S/PDIF output to AES input

No. Don't buy those transformers. They are designed to convert AES 110 ohm to match the impedance of a 75 ohm video cable for long cable runs. It will NOT convert from S/PDIF to AES.

"...our I/O adapters are designed to passively convert all standard AES/EBU digital audio signals from 110 ohm/XLR3 Output (@ 4.5 Volts) to a 75 ohm BNC coaxial cable and then back again to a 110 ohm/XLR3 Input (200mV min)"

http://www.rane.com/note149.html

"Remember that even though the audio data is the same between AES3 and S/PDIF, they have different subcode formats. AES3 converted to 75-ohm coax is not S/PDIF, and S/PDIF converted to XLR balanced is not AES3. Nor is AES3id 75-ohm BNC the same as 75-ohm RCA S/PDIF -- it may work, but it is not the same. They are still in their native format; just the transmission medium has changed. Going from S/PDIF to AES3 has a higher degree of success than the other way around. AES3 signals often are not recognized as valid by S/PDIF inputs. Whether they will work in your application depends on the equipment chosen."

Radio Design Labs make a bunch of neat adapters. This S/PDIF/AES converter even has an optical port

http://www.rdlnet.com/product.php?page=22

real converters:

http://www.sweetwater.com/c741--Misc_Digital_Converters
http://www.murraypro.com/spdif.htm
http://www.coffeysound.com/product.php?productid=541

You can try a simple adapter (RCA to XLR) and it may work but I'd recommend a real converter.
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Old 05-03-2007, 09:51 AM
Dan Tinen Dan Tinen is offline
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Default Re: Converting S/PDIF output to AES input

Thanks for the information, Park. The Rane paper is particularly authoritative and I appreciate their work. I seem to recall that very few products actually use "S/PDIF" (which implies use of track #s in subcode). For this reason, some Japanese companies labeled the digital jacks "IEC958" or "CP340" to point this out.

My guess is that in my particular situation--from an OO2 to a Crane Song D/A--the subcodes will not be a problem, since this application doesn't care about track IDs, etc. Going from an external (Lavry) A/D (AES out) to the 002 (SPDIF in) will probably work using the Canare adapter with its -10 dB pad, since the main difference is the voltage.

Going the other way--from the 002 SPDIF out into a Crane Song--is potentially a bigger problem, whether the voltage from a 1-volt SPDIF output will be "read" by an AES input expecting a higher voltage. But, as people have noted, the hardware is forgiving enough these days that it might be able to read it. I don't know at this point if the Crane has a transformer-balanced AES input, or how sensitive it is. But why doesn't Canare (or someone) make a step-up transformer in that convenient in-line format? It seems like an easier thing than using active hardware.

Cost of the Canares ranges from $19 to $34 depending on dealer. The RDL and Hosa boxes are in the $90 range, (plus power supply in RDL's case). I'm tempted to try the Canares and see how they work in my situation, it seems a little more kosher than simply using a hard-wired adapter.

I'd love to hear from 002 users who have used its SPDIF I/O with AES equipment. Anyone?
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Old 05-03-2007, 11:10 AM
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Default Re: Converting S/PDIF output to AES input

Not a problem- a transformer will help, especially with longer cable runs, but it is not going to make a huge difference. My entire rig is AES-based. I run in to all the various LE and Mpowered systems and they work just fine. If you aren't using the transformers, try to keep your cable runs to a few feet long.

--Ben
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Old 08-31-2021, 12:17 PM
Artysan Artysan is offline
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Default Re: Converting S/PDIF output to AES input

Quote:
Originally Posted by Park Seward View Post
No. Don't buy those transformers. They are designed to convert AES 110 ohm to match the impedance of a 75 ohm video cable for long cable runs. It will NOT convert from S/PDIF to AES.
This information is inaccurate at best and self-serving at its worst, Park. The digital audio data is fully and comprehensively converted by a transformer, particularly going in the direction of SPDIF > AES. Spec is met 100%.

This is daily routine in cost-no-object professional applications I have employed countless times where the requirement is to bridge the formats electrically and extract the audio flawlessly. So, yes. Buy those transformers. Your SPDIF coax digital audio will become flawless AES balanced digital audio, which was the point, no?
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Old 08-31-2021, 01:10 PM
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Default Re: Converting S/PDIF output to AES input

IF (and a very big if) your cable length is short like one meter, you can connect SPDIF and AES just the same way you can connect unbalanced and balanced analog audio. You only need to wire pin 2 of XLR to the tip of RCA jack and pin 3 of XLR to sleeve of RCA jack (with pin one being ground and should be disconnected at the RCA end).

Strictly speaking, channel status and other subcode data is formatted differently between AES and SPDIF but very little equipment bother to send or read the full subcode data set anyway.
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Old 08-31-2021, 01:48 PM
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Default Converting S/PDIF output to AES input

Quote:
Originally Posted by Artysan View Post
This information is inaccurate at best and self-serving at its worst, Park. The digital audio data is fully and comprehensively converted by a transformer, particularly going in the direction of SPDIF > AES. Spec is met 100%.

This is daily routine in cost-no-object professional applications I have employed countless times where the requirement is to bridge the formats electrically and extract the audio flawlessly. So, yes. Buy those transformers. Your SPDIF coax digital audio will become flawless AES balanced digital audio, which was the point, no?

That old post is not wrong though he did take the hardline without tempering it with real world application.

The digital data is not “fully and comprehensively converted”. The only thing converted is the interconnection medium. The data remains absolutely unchanged. The reason it’s permissible to do this between AES and S/PDIF is because the common digital receiver chips used in this application are designed to handle both often with the only difference being the configuration for voltage, impedance and common/differential transmission.
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  #10  
Old 08-31-2021, 05:00 PM
Artysan Artysan is offline
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Default Re: Converting S/PDIF output to AES input

Quote:
Originally Posted by Top Jimmy View Post
That old post is not wrong though he did take the hardline without tempering it with real world application.

The digital data is not “fully and comprehensively converted”.
I very specifically said that “the digital audio data is fully and comprehensively converted” which it is. Does anyone in this situation actually care at all about metadata or header information, which is likely nonexistent?

Words matter.
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