Coax spdif to AES/EBU - why so expensive?

[Steve Jorgensen]

I own a MOTU 896 Original version, and it has 2 kinds of digital input. It
has an optical ADAT input that does not understand spdif signals, and an
AES/EBU input that presumably doesn't understand spdif signals that have been
only impedance matched.

Since the formats are so similar, I thought it would be no problem to find a
converter that would let me take the 24-bit coax spdif output from my VF-1
directly into the AES/EBU input on my 896 (I only need 44.1/48K rates if that
makes any difference).

Nope - the simple Hosa and Behringer products are 16-bit only, and the
cheapest converter I can find that can do the job at 24-bit is the M-Audio Co3
which is nice, but totally overkill with respect to other features I don't
need. Furthermore, it seems overpriced, when a perfectly decent 8-channel
A/D/A - ADAT unit can be had from Behringer with a street price of $230.

Can it really cost almost as much to convert one stereo coax spdif signal to
AES/EBU as it does to convert 8 channels of audio to and from 24-bit ADAT at
what all the reviewers say is pretty decent quality?

[Mike Rivers]

In article > writes:

> Can it really cost almost as much to convert one stereo coax spdif signal to
> AES/EBU as it does to convert 8 channels of audio to and from 24-bit ADAT at
> what all the reviewers say is pretty decent quality?

No. Most of the time all you need is a hard-wired adapter, but worst
case you'll need a transformer (balun) which is about $25 and probably
some RCA-BNC adapters.

Understand that while the fiber optic lightpipe and connectors are the
same for S/PDIF and ADAT optical digital interfaces, the protocols are
different and won't work together except on devices which have been
designed for it (some Frontier Designs audio interface cards come to
mind).




--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo

[Mike Rivers]

In article > writes:

> Can it really cost almost as much to convert one stereo coax spdif signal to
> AES/EBU as it does to convert 8 channels of audio to and from 24-bit ADAT at
> what all the reviewers say is pretty decent quality?

No. Most of the time all you need is a hard-wired adapter, but worst
case you'll need a transformer (balun) which is about $25 and probably
some RCA-BNC adapters.

Understand that while the fiber optic lightpipe and connectors are the
same for S/PDIF and ADAT optical digital interfaces, the protocols are
different and won't work together except on devices which have been
designed for it (some Frontier Designs audio interface cards come to
mind).




--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo

[Steve Jorgensen]

On 14 Jul 2004 18:05:00 -0400, (Mike Rivers) wrote:

>
>In article > writes:
>
>> Can it really cost almost as much to convert one stereo coax spdif signal to
>> AES/EBU as it does to convert 8 channels of audio to and from 24-bit ADAT at
>> what all the reviewers say is pretty decent quality?
>
>No. Most of the time all you need is a hard-wired adapter, but worst
>case you'll need a transformer (balun) which is about $25 and probably
>some RCA-BNC adapters.
>
>Understand that while the fiber optic lightpipe and connectors are the
>same for S/PDIF and ADAT optical digital interfaces, the protocols are
>different and won't work together except on devices which have been
>designed for it (some Frontier Designs audio interface cards come to
>mind).

My understanding is that there is aomthing like a 1-bit difference in the
packet header for AES/EBU vs spdif, and some devices tolerate the difference,
and others don't. Is there any way (other than trying it) to know if the 896
does or doesn't? Also, what is the correct kind of transformer to convert the
impedance?

[Steve Jorgensen]

On 14 Jul 2004 18:05:00 -0400, (Mike Rivers) wrote:

>
>In article > writes:
>
>> Can it really cost almost as much to convert one stereo coax spdif signal to
>> AES/EBU as it does to convert 8 channels of audio to and from 24-bit ADAT at
>> what all the reviewers say is pretty decent quality?
>
>No. Most of the time all you need is a hard-wired adapter, but worst
>case you'll need a transformer (balun) which is about $25 and probably
>some RCA-BNC adapters.
>
>Understand that while the fiber optic lightpipe and connectors are the
>same for S/PDIF and ADAT optical digital interfaces, the protocols are
>different and won't work together except on devices which have been
>designed for it (some Frontier Designs audio interface cards come to
>mind).

My understanding is that there is aomthing like a 1-bit difference in the
packet header for AES/EBU vs spdif, and some devices tolerate the difference,
and others don't. Is there any way (other than trying it) to know if the 896
does or doesn't? Also, what is the correct kind of transformer to convert the
impedance?

[Scott Dorsey]

Steve Jorgensen > wrote:
>packet header for AES/EBU vs spdif, and some devices tolerate the difference,
>and others don't. Is there any way (other than trying it) to know if the 896
>does or doesn't? Also, what is the correct kind of transformer to convert the
>impedance?

There is no longer any AES/EBU and no longer any S-PDIF. What we now have
is IEC 958.

You can get balanced IEC 958, or unbalanced IEC 958. You can get IEC 958 with
professional subcode, or with consumer subcode.

MOST non-Panasonic equipment will accept either subcode variant without any
problem (and it's way more than a 1-bit difference). Not all will, though.

The transformers from Canare (which Markertek stocks) will convert 110 ohm
balanced line to 75 ohm unbalanced line so that you can connect unbalanced
IEC 958 gear to balanced IEC 958 gear. They will not alter the subcode.

The old AES/EBU standard is comparable to IEC 958 balanced/professional.
The old S-PDIF standard is comparable to IEC 958 unbalanced/consumer. BUT
there are other possibilities which do not meet either of the older standards
but are valid under the new standard.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Scott Dorsey]

Steve Jorgensen > wrote:
>packet header for AES/EBU vs spdif, and some devices tolerate the difference,
>and others don't. Is there any way (other than trying it) to know if the 896
>does or doesn't? Also, what is the correct kind of transformer to convert the
>impedance?

There is no longer any AES/EBU and no longer any S-PDIF. What we now have
is IEC 958.

You can get balanced IEC 958, or unbalanced IEC 958. You can get IEC 958 with
professional subcode, or with consumer subcode.

MOST non-Panasonic equipment will accept either subcode variant without any
problem (and it's way more than a 1-bit difference). Not all will, though.

The transformers from Canare (which Markertek stocks) will convert 110 ohm
balanced line to 75 ohm unbalanced line so that you can connect unbalanced
IEC 958 gear to balanced IEC 958 gear. They will not alter the subcode.

The old AES/EBU standard is comparable to IEC 958 balanced/professional.
The old S-PDIF standard is comparable to IEC 958 unbalanced/consumer. BUT
there are other possibilities which do not meet either of the older standards
but are valid under the new standard.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Steve Jorgensen]

On 15 Jul 2004 10:51:02 -0400, (Scott Dorsey) wrote:

>Steve Jorgensen > wrote:
>>packet header for AES/EBU vs spdif, and some devices tolerate the difference,
>>and others don't. Is there any way (other than trying it) to know if the 896
>>does or doesn't? Also, what is the correct kind of transformer to convert the
>>impedance?
>
>There is no longer any AES/EBU and no longer any S-PDIF. What we now have
>is IEC 958.
>
>You can get balanced IEC 958, or unbalanced IEC 958. You can get IEC 958 with
>professional subcode, or with consumer subcode.
>
>MOST non-Panasonic equipment will accept either subcode variant without any
>problem (and it's way more than a 1-bit difference). Not all will, though.
>
>The transformers from Canare (which Markertek stocks) will convert 110 ohm
>balanced line to 75 ohm unbalanced line so that you can connect unbalanced
>IEC 958 gear to balanced IEC 958 gear. They will not alter the subcode.
>
>The old AES/EBU standard is comparable to IEC 958 balanced/professional.
>The old S-PDIF standard is comparable to IEC 958 unbalanced/consumer. BUT
>there are other possibilities which do not meet either of the older standards
>but are valid under the new standard.
>--scott

Thanks, that's very helpful to know. I guess it still doesn't tell me if my
896 Original will accept the digital signal from my Boss VF-1, but I guess
it's worth a try. Why bother, you ask? We use the VF-1 a lot, so doing that
would free up 2 analog inputs.

[Steve Jorgensen]

On 15 Jul 2004 10:51:02 -0400, (Scott Dorsey) wrote:

>Steve Jorgensen > wrote:
>>packet header for AES/EBU vs spdif, and some devices tolerate the difference,
>>and others don't. Is there any way (other than trying it) to know if the 896
>>does or doesn't? Also, what is the correct kind of transformer to convert the
>>impedance?
>
>There is no longer any AES/EBU and no longer any S-PDIF. What we now have
>is IEC 958.
>
>You can get balanced IEC 958, or unbalanced IEC 958. You can get IEC 958 with
>professional subcode, or with consumer subcode.
>
>MOST non-Panasonic equipment will accept either subcode variant without any
>problem (and it's way more than a 1-bit difference). Not all will, though.
>
>The transformers from Canare (which Markertek stocks) will convert 110 ohm
>balanced line to 75 ohm unbalanced line so that you can connect unbalanced
>IEC 958 gear to balanced IEC 958 gear. They will not alter the subcode.
>
>The old AES/EBU standard is comparable to IEC 958 balanced/professional.
>The old S-PDIF standard is comparable to IEC 958 unbalanced/consumer. BUT
>there are other possibilities which do not meet either of the older standards
>but are valid under the new standard.
>--scott

Thanks, that's very helpful to know. I guess it still doesn't tell me if my
896 Original will accept the digital signal from my Boss VF-1, but I guess
it's worth a try. Why bother, you ask? We use the VF-1 a lot, so doing that
would free up 2 analog inputs.

[Scott Dorsey]

Steve Jorgensen > wrote:
>Thanks, that's very helpful to know. I guess it still doesn't tell me if my
>896 Original will accept the digital signal from my Boss VF-1, but I guess
>it's worth a try. Why bother, you ask? We use the VF-1 a lot, so doing that
>would free up 2 analog inputs.

If they both meet the IEC standard, there should be no problem. Sadly not
everything that claims to meet the standard actually does.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Scott Dorsey]

Steve Jorgensen > wrote:
>Thanks, that's very helpful to know. I guess it still doesn't tell me if my
>896 Original will accept the digital signal from my Boss VF-1, but I guess
>it's worth a try. Why bother, you ask? We use the VF-1 a lot, so doing that
>would free up 2 analog inputs.

If they both meet the IEC standard, there should be no problem. Sadly not
everything that claims to meet the standard actually does.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Richard Whitehouse]

slightly OT question:

If 75-ohm coaxial RCA cable (also called video cable, I believe) is the
correct cable to use for unbalanced IEC 958 (S-PDIF) connections, what's
the difference between that kind of RCA cable and regular audio RCA cable?
That is, what's the ohm rating of standard RCA audio cables?

I found one place that sells RCA audio cables, and in the specs it says
"Nominal impdenance: 54 ohms" - does that sound about right?



**************************************
** http://www.richardwhitehouse.ca **
**************************************

[Richard Whitehouse]

slightly OT question:

If 75-ohm coaxial RCA cable (also called video cable, I believe) is the
correct cable to use for unbalanced IEC 958 (S-PDIF) connections, what's
the difference between that kind of RCA cable and regular audio RCA cable?
That is, what's the ohm rating of standard RCA audio cables?

I found one place that sells RCA audio cables, and in the specs it says
"Nominal impdenance: 54 ohms" - does that sound about right?



**************************************
** http://www.richardwhitehouse.ca **
**************************************

[Scott Dorsey]

Richard Whitehouse > wrote:
>
>If 75-ohm coaxial RCA cable (also called video cable, I believe) is the
>correct cable to use for unbalanced IEC 958 (S-PDIF) connections, what's
>the difference between that kind of RCA cable and regular audio RCA cable?
>That is, what's the ohm rating of standard RCA audio cables?

Regular audio cable is normally not rated for impedance. It could be one
thing, it could be another. Normally the conductor spacing is not well
enough controlled for them to even state the impedance of the cable, since
it doesn't matter for audio applications.

>I found one place that sells RCA audio cables, and in the specs it says
>"Nominal impdenance: 54 ohms" - does that sound about right?

Could be. I bet the tolerances are wide as hell, though. One day it might
be 54, another day it might be 52 or 53. There's no reason to tightly
control this stuff on an audio cable.

If you are curious, you can measure it yourself with a pulse generator and
a scope. Put a pulse down the line and look at it with a scope, then adjust
a pot on the far end of the line until the square wave is nice and square.
When you do, measure the value of the pot and it will be equal to the
characteristic impedance of the cable.

Even the 1 KC square wave generator on the old Tek boatanchor scopes is good
enough if you have a few hundred feet of cable.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Scott Dorsey]

Richard Whitehouse > wrote:
>
>If 75-ohm coaxial RCA cable (also called video cable, I believe) is the
>correct cable to use for unbalanced IEC 958 (S-PDIF) connections, what's
>the difference between that kind of RCA cable and regular audio RCA cable?
>That is, what's the ohm rating of standard RCA audio cables?

Regular audio cable is normally not rated for impedance. It could be one
thing, it could be another. Normally the conductor spacing is not well
enough controlled for them to even state the impedance of the cable, since
it doesn't matter for audio applications.

>I found one place that sells RCA audio cables, and in the specs it says
>"Nominal impdenance: 54 ohms" - does that sound about right?

Could be. I bet the tolerances are wide as hell, though. One day it might
be 54, another day it might be 52 or 53. There's no reason to tightly
control this stuff on an audio cable.

If you are curious, you can measure it yourself with a pulse generator and
a scope. Put a pulse down the line and look at it with a scope, then adjust
a pot on the far end of the line until the square wave is nice and square.
When you do, measure the value of the pot and it will be equal to the
characteristic impedance of the cable.

Even the 1 KC square wave generator on the old Tek boatanchor scopes is good
enough if you have a few hundred feet of cable.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Richard Whitehouse]

>> In article >,
>> (Scott Dorsey) wrote:
>> >That is, what's the ohm rating of standard RCA audio cables?
>>
>> Regular audio cable is normally not rated for impedance. It could be one
>> thing, it could be another. Normally the conductor spacing is not well
>> enough controlled for them to even state the impedance of the cable, since
>> it doesn't matter for audio applications.

Thanks, Scott


**************************************
** http://www.richardwhitehouse.ca **
**************************************

[Richard Whitehouse]

>> In article >,
>> (Scott Dorsey) wrote:
>> >That is, what's the ohm rating of standard RCA audio cables?
>>
>> Regular audio cable is normally not rated for impedance. It could be one
>> thing, it could be another. Normally the conductor spacing is not well
>> enough controlled for them to even state the impedance of the cable, since
>> it doesn't matter for audio applications.

Thanks, Scott


**************************************
** http://www.richardwhitehouse.ca **
**************************************

[Kurt Albershardt]

Scott Dorsey wrote:

> Richard Whitehouse > wrote:
>
>> If 75-ohm coaxial RCA cable (also called video cable, I believe) is the
>> correct cable to use for unbalanced IEC 958 (S-PDIF) connections, what's
>> the difference between that kind of RCA cable and regular audio RCA cable?
>> That is, what's the ohm rating of standard RCA audio cables?
>
>
> Regular audio cable is normally not rated for impedance. It could be one
> thing, it could be another. Normally the conductor spacing is not well
> enough controlled for them to even state the impedance of the cable, since
> it doesn't matter for audio applications.
>
>
>> I found one place that sells RCA audio cables, and in the specs it says
>> "Nominal impdenance: 54 ohms" - does that sound about right?
>
>
> Could be. I bet the tolerances are wide as hell, though. One day it might
> be 54, another day it might be 52 or 53. There's no reason to tightly
> control this stuff on an audio cable.

None of which is particularly critical for short runs of digital audio.

[Kurt Albershardt]

Scott Dorsey wrote:

> Richard Whitehouse > wrote:
>
>> If 75-ohm coaxial RCA cable (also called video cable, I believe) is the
>> correct cable to use for unbalanced IEC 958 (S-PDIF) connections, what's
>> the difference between that kind of RCA cable and regular audio RCA cable?
>> That is, what's the ohm rating of standard RCA audio cables?
>
>
> Regular audio cable is normally not rated for impedance. It could be one
> thing, it could be another. Normally the conductor spacing is not well
> enough controlled for them to even state the impedance of the cable, since
> it doesn't matter for audio applications.
>
>
>> I found one place that sells RCA audio cables, and in the specs it says
>> "Nominal impdenance: 54 ohms" - does that sound about right?
>
>
> Could be. I bet the tolerances are wide as hell, though. One day it might
> be 54, another day it might be 52 or 53. There's no reason to tightly
> control this stuff on an audio cable.

None of which is particularly critical for short runs of digital audio.

[Mike Rivers]

In article > writes:

> My understanding is that there is aomthing like a 1-bit difference in the
> packet header for AES/EBU vs spdif, and some devices tolerate the difference,
> and others don't.

There's more than one bit difference. There's one bit that says
whether a bunch of other bits should be interpreted in one way
(IEC-958/1) or the other (IEC-958/2).

There's also a difference in nominal signal between the pro and
consumer formats, but most receivers are tolerant of either.

> Is there any way (other than trying it) to know if the 896
> does or doesn't?

Ask MOTU. But it's quicker to try it.

> Also, what is the correct kind of transformer to convert the
> impedance?

75 to 110 ohm. Here's one you can order from Markertek, but note that
the 75 ohm side has a BNC connector on it. You'll probalby need an
adapter on that to convert it to an RCA jack. Radio Shack has those,
or you can order one (or a cable with a BNC on one end and RCA on the
other end) from Markertek and get it all in one place.

http://www.markertek.com/SearchProduct.asp?item=NA%2DBF&off=3



--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo

[Mike Rivers]

In article > writes:

> My understanding is that there is aomthing like a 1-bit difference in the
> packet header for AES/EBU vs spdif, and some devices tolerate the difference,
> and others don't.

There's more than one bit difference. There's one bit that says
whether a bunch of other bits should be interpreted in one way
(IEC-958/1) or the other (IEC-958/2).

There's also a difference in nominal signal between the pro and
consumer formats, but most receivers are tolerant of either.

> Is there any way (other than trying it) to know if the 896
> does or doesn't?

Ask MOTU. But it's quicker to try it.

> Also, what is the correct kind of transformer to convert the
> impedance?

75 to 110 ohm. Here's one you can order from Markertek, but note that
the 75 ohm side has a BNC connector on it. You'll probalby need an
adapter on that to convert it to an RCA jack. Radio Shack has those,
or you can order one (or a cable with a BNC on one end and RCA on the
other end) from Markertek and get it all in one place.

http://www.markertek.com/SearchProduct.asp?item=NA%2DBF&off=3



--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo

[Mike]

(Scott Dorsey) wrote in message >...
> Steve Jorgensen > wrote:
> >packet header for AES/EBU vs spdif, and some devices tolerate the difference,
> >and others don't. Is there any way (other than trying it) to know if the 896
> >does or doesn't? Also, what is the correct kind of transformer to convert the
> >impedance?
>
> There is no longer any AES/EBU and no longer any S-PDIF. What we now have
> is IEC 958.
>
> You can get balanced IEC 958, or unbalanced IEC 958. You can get IEC 958 with
> professional subcode, or with consumer subcode.
>
> MOST non-Panasonic equipment will accept either subcode variant without any
> problem (and it's way more than a 1-bit difference). Not all will, though.
>
> The transformers from Canare (which Markertek stocks) will convert 110 ohm
> balanced line to 75 ohm unbalanced line so that you can connect unbalanced
> IEC 958 gear to balanced IEC 958 gear. They will not alter the subcode.
>
> The old AES/EBU standard is comparable to IEC 958 balanced/professional.
> The old S-PDIF standard is comparable to IEC 958 unbalanced/consumer. BUT
> there are other possibilities which do not meet either of the older standards
> but are valid under the new standard.
> --scott

Whose on first?

Mike http://www.mmeproductions.com

[Mike]

(Scott Dorsey) wrote in message >...
> Steve Jorgensen > wrote:
> >packet header for AES/EBU vs spdif, and some devices tolerate the difference,
> >and others don't. Is there any way (other than trying it) to know if the 896
> >does or doesn't? Also, what is the correct kind of transformer to convert the
> >impedance?
>
> There is no longer any AES/EBU and no longer any S-PDIF. What we now have
> is IEC 958.
>
> You can get balanced IEC 958, or unbalanced IEC 958. You can get IEC 958 with
> professional subcode, or with consumer subcode.
>
> MOST non-Panasonic equipment will accept either subcode variant without any
> problem (and it's way more than a 1-bit difference). Not all will, though.
>
> The transformers from Canare (which Markertek stocks) will convert 110 ohm
> balanced line to 75 ohm unbalanced line so that you can connect unbalanced
> IEC 958 gear to balanced IEC 958 gear. They will not alter the subcode.
>
> The old AES/EBU standard is comparable to IEC 958 balanced/professional.
> The old S-PDIF standard is comparable to IEC 958 unbalanced/consumer. BUT
> there are other possibilities which do not meet either of the older standards
> but are valid under the new standard.
> --scott

Whose on first?

Mike http://www.mmeproductions.com

[Moran, Doug - Denison]

On 15 Jul 2004, Mike Rivers wrote:

> > Also, what is the correct kind of transformer to convert the
> > impedance?
>
> 75 to 110 ohm. Here's one you can order from Markertek, but note that
> the 75 ohm side has a BNC connector on it. You'll probalby need an
> adapter on that to convert it to an RCA jack. Radio Shack has those,
> or you can order one (or a cable with a BNC on one end and RCA on the
> other end) from Markertek and get it all in one place.
>
> http://www.markertek.com/SearchProduct.asp?item=NA%2DBF&off=3

I'm using a set of the Canare XLR To BNC Impedance Transformers with the
BNC to RCA adapters and it is working great. ~$55 solution.

Doug

[Moran, Doug - Denison]

On 15 Jul 2004, Mike Rivers wrote:

> > Also, what is the correct kind of transformer to convert the
> > impedance?
>
> 75 to 110 ohm. Here's one you can order from Markertek, but note that
> the 75 ohm side has a BNC connector on it. You'll probalby need an
> adapter on that to convert it to an RCA jack. Radio Shack has those,
> or you can order one (or a cable with a BNC on one end and RCA on the
> other end) from Markertek and get it all in one place.
>
> http://www.markertek.com/SearchProduct.asp?item=NA%2DBF&off=3

I'm using a set of the Canare XLR To BNC Impedance Transformers with the
BNC to RCA adapters and it is working great. ~$55 solution.

Doug

[David Satz]

Steve Jorgensen wrote:

> Can it really cost almost as much to convert one stereo coax spdif
> signal to AES/EBU as it does to convert 8 channels of audio to and
> from 24-bit ADAT at what all the reviewers say is pretty decent quality?

The two interface types use a similar format for carrying the main
channel data, but they use the channel status bits differently and also
have different limits as to the number of bits per sample. As an example,
if I recall correctly S-P/DIF uses the same status bit for "pre-emphasis"
that AES/EBU uses for its "consumer/professional" flag, or the like.
Thus converting correctly between the two signals cannot be done with a
simple mechanical adapter or transformer; it is necessary to extract the
bits and reassemble them appropriately into a new data stream. Either it
has to translate those flag and status bits or insert fake ones.

The price of units that can do this has come down from the $500 range to
the $200-list-price (but discounted by dealers) range. Be glad of that.