Eeek! Snakes! (REPOST, with first pgf intact)

[Frank Stearns]

(Don't know WHY this first para got lopped of the first post of this; hope
it makes it this time; sorry for the extra bandwidth.)

I need to build a few snakes for a location recording operation, probably
in four or eight channel increments. Interestingly, the "best buys" in the
Belden line (in terms of cost per foot per pair) appear to be eight
channel configurations.

I've been looking at several cable samples (the folks at Belden are great,
BTW), and have come down to a few selections, but am now seeking a little
wisdom

I can buy Belden AES-EBU cable (1800 and 7890 series) for analog snake
use, and then also be ready to send digital data down the snake when I
can afford to put pres and converters on stage. AES-EBU cable is a bit
more expensive, but now I'm wondering whether I'd ever run AES-EBU for
long haul data, or whether I'd wind up using something else, like the
appropriate baluns and a Cat6 snake of some type.

The AES-EBU cable is 13 pf/ft; the standard analog stuff (1900 series) is
26 pf. Others have posted that 26 pf/ft should not be an audible issue for
at least 600 ft. It'd be rare that I'm over 400 ft. I also wonder if the
higher capacitance might help a little with RF immunity (short of going to
star quad which, at nearly 40 pf/ft, would probably be too reactive at
those lengths).

So, should I lean toward AES-EBU whether I ever send digital or not, or
stick with the regular analog stuff?

The other question is size: for mic runs under, say, 500 ft, do I gain
much by going to 24 gauge v. 26? That 24 gauge 180x series is big stuff;
might become a mechanical issue (rolling, transporting, etc).

Thanks in advance,

Frank
--

[Stephen Anderson]

Frank Stearns wrote:

> (Don't know WHY this first para got lopped of the first post of this; hope
> it makes it this time; sorry for the extra bandwidth.)
>
> I need to build a few snakes for a location recording operation, probably
> in four or eight channel increments. Interestingly, the "best buys" in the
> Belden line (in terms of cost per foot per pair) appear to be eight
> channel configurations.
>
> I've been looking at several cable samples (the folks at Belden are great,
> BTW), and have come down to a few selections, but am now seeking a little
> wisdom

I have been doing all installations with AES/EBU compliant cable for
some time now, for exactly the forward thinking flexibility you
mentioned. Listening tests, as well as digital measurements, have been
positive. In the last fixed install I did, we tested 150' runs with no
signal degradation audible in digital mode. While the Belden stuff is
fine, I have been using Gepco's multipair, as it has comparable specs,
but is cheaper by quite a bit.

>
> I can buy Belden AES-EBU cable (1800 and 7890 series) for analog snake
> use, and then also be ready to send digital data down the snake when I
> can afford to put pres and converters on stage. AES-EBU cable is a bit
> more expensive, but now I'm wondering whether I'd ever run AES-EBU for
> long haul data, or whether I'd wind up using something else, like the
> appropriate baluns and a Cat6 snake of some type.

Belden does have an interesting white paper on their web site about
Cat5e & Cat6 being used for audio, video, every damn thing, with the
proper baluns for unbalanced signal families. While I think that's the
wave of the future, virtually no one I know is prepared to embrace that
concept now.
>
> The AES-EBU cable is 13 pf/ft; the standard analog stuff (1900 series) is
> 26 pf. Others have posted that 26 pf/ft should not be an audible issue for
> at least 600 ft. It'd be rare that I'm over 400 ft. I also wonder if the
> higher capacitance might help a little with RF immunity (short of going to
> star quad which, at nearly 40 pf/ft, would probably be too reactive at
> those lengths).

Respectfully, that's like saying that rolling off all the highs will
help cure pesky noise issues. Cable capacitance is really not an issue
in RF rejection, and low capacitance helps with group delay and phase
distortion. Proper grounding, solid connections that don't detect RF,
good balanced inputs with really good CMRR and RF rejection filtering
built in will make the difference.
>
> So, should I lean toward AES-EBU whether I ever send digital or not, or
> stick with the regular analog stuff?
>
> The other question is size: for mic runs under, say, 500 ft, do I gain
> much by going to 24 gauge v. 26? That 24 gauge 180x series is big stuff;
> might become a mechanical issue (rolling, transporting, etc).

AES/EBU cabling is always going to be thicker, due to the thicker foam
dielectric used to achieve the low capacitance. Hence, 16 pr AES/EBU
will be about the same diameter (roughly) as conventional audio
multipair, AWG size being equal.

For fixed installs, sometimes cable throughways dictate 24AWG. For live,
I would lean toward 22AWG. FYI, the old standard for audio multipair,
Belden 8773 27 pr., was 22AWG. Look at the Ohms per foot, do a few
calculations, see if it changes the situation when factored against the
source and input impedance. For my money, the thicker wire will just be
more robust physically, albeit somewhat heavier.

Good Luck!
>
> Thanks in advance,
>
> Frank

--
Stephen Anderson
>
~At the end of the day, it's all about the music

[Stephen Anderson]

Frank Stearns wrote:

> (Don't know WHY this first para got lopped of the first post of this; hope
> it makes it this time; sorry for the extra bandwidth.)
>
> I need to build a few snakes for a location recording operation, probably
> in four or eight channel increments. Interestingly, the "best buys" in the
> Belden line (in terms of cost per foot per pair) appear to be eight
> channel configurations.
>
> I've been looking at several cable samples (the folks at Belden are great,
> BTW), and have come down to a few selections, but am now seeking a little
> wisdom

I have been doing all installations with AES/EBU compliant cable for
some time now, for exactly the forward thinking flexibility you
mentioned. Listening tests, as well as digital measurements, have been
positive. In the last fixed install I did, we tested 150' runs with no
signal degradation audible in digital mode. While the Belden stuff is
fine, I have been using Gepco's multipair, as it has comparable specs,
but is cheaper by quite a bit.

>
> I can buy Belden AES-EBU cable (1800 and 7890 series) for analog snake
> use, and then also be ready to send digital data down the snake when I
> can afford to put pres and converters on stage. AES-EBU cable is a bit
> more expensive, but now I'm wondering whether I'd ever run AES-EBU for
> long haul data, or whether I'd wind up using something else, like the
> appropriate baluns and a Cat6 snake of some type.

Belden does have an interesting white paper on their web site about
Cat5e & Cat6 being used for audio, video, every damn thing, with the
proper baluns for unbalanced signal families. While I think that's the
wave of the future, virtually no one I know is prepared to embrace that
concept now.
>
> The AES-EBU cable is 13 pf/ft; the standard analog stuff (1900 series) is
> 26 pf. Others have posted that 26 pf/ft should not be an audible issue for
> at least 600 ft. It'd be rare that I'm over 400 ft. I also wonder if the
> higher capacitance might help a little with RF immunity (short of going to
> star quad which, at nearly 40 pf/ft, would probably be too reactive at
> those lengths).

Respectfully, that's like saying that rolling off all the highs will
help cure pesky noise issues. Cable capacitance is really not an issue
in RF rejection, and low capacitance helps with group delay and phase
distortion. Proper grounding, solid connections that don't detect RF,
good balanced inputs with really good CMRR and RF rejection filtering
built in will make the difference.
>
> So, should I lean toward AES-EBU whether I ever send digital or not, or
> stick with the regular analog stuff?
>
> The other question is size: for mic runs under, say, 500 ft, do I gain
> much by going to 24 gauge v. 26? That 24 gauge 180x series is big stuff;
> might become a mechanical issue (rolling, transporting, etc).

AES/EBU cabling is always going to be thicker, due to the thicker foam
dielectric used to achieve the low capacitance. Hence, 16 pr AES/EBU
will be about the same diameter (roughly) as conventional audio
multipair, AWG size being equal.

For fixed installs, sometimes cable throughways dictate 24AWG. For live,
I would lean toward 22AWG. FYI, the old standard for audio multipair,
Belden 8773 27 pr., was 22AWG. Look at the Ohms per foot, do a few
calculations, see if it changes the situation when factored against the
source and input impedance. For my money, the thicker wire will just be
more robust physically, albeit somewhat heavier.

Good Luck!
>
> Thanks in advance,
>
> Frank

--
Stephen Anderson
>
~At the end of the day, it's all about the music

[Arny Krueger]

Frank Stearns wrote:
> (Don't know WHY this first para got lopped of the first post of this;
> hope it makes it this time; sorry for the extra bandwidth.)
>
> I need to build a few snakes for a location recording operation,
> probably in four or eight channel increments. Interestingly, the
> "best buys" in the Belden line (in terms of cost per foot per pair)
> appear to be eight channel configurations.
>
> I've been looking at several cable samples (the folks at Belden are
> great, BTW), and have come down to a few selections, but am now
> seeking a little wisdom
>
> I can buy Belden AES-EBU cable (1800 and 7890 series) for analog snake
> use, and then also be ready to send digital data down the snake when
> I can afford to put pres and converters on stage. AES-EBU cable is a
> bit more expensive, but now I'm wondering whether I'd ever run
> AES-EBU for long haul data, or whether I'd wind up using something
> else, like the appropriate baluns and a Cat6 snake of some type.

> The AES-EBU cable is 13 pf/ft; the standard analog stuff (1900
> series) is 26 pf. Others have posted that 26 pf/ft should not be an
> audible issue for at least 600 ft. It'd be rare that I'm over 400 ft.
> I also wonder if the higher capacitance might help a little with RF
> immunity (short of going to star quad which, at nearly 40 pf/ft,
> would probably be too reactive at those lengths).

> So, should I lean toward AES-EBU whether I ever send digital or not,
> or stick with the regular analog stuff?

If you are going to send massive amounts of digital in the 21st century, you
are more likely to be using something like an AudioRail, not a massive snake
of SP/DIF or AES/EBU cables.

> The other question is size: for mic runs under, say, 500 ft, do I gain
> much by going to 24 gauge v. 26? That 24 gauge 180x series is big
> stuff; might become a mechanical issue (rolling, transporting, etc).

Resistance of wire per foot

20 .0119
22 .0190
24 .0302
26 .0480

Resistance of wire per 500 foot of 2-conductor cable, or 1,000 feet of wire

20 11.9
22 19.0
24 30.2
26 48.0

Attenuation into 1000 ohm load:

20 0.1 dB
22 0.16 dB
24 0.26 dB
26 0.41 dB

Capacitance per 500 feet of cable

13 pF/ft - 6,500 pf or 0.0065 uF
26 pF/ft - 13,000 pf or 0.013 uF

Frequency of 3 dB Attenuation with 100 ohm source impedance:

13 pF/ft - 6,500 pf or 0.0065 uF F3=244 KHz F1= 48 KHz F0.1=24 KHz
26 pF/ft - 13,000 pf or 0.013 uF F3 = 122 KHz F1 = 24 Khz F0.1 - 12 KHz

IOW, its not going to matter very much what you pick.

[Arny Krueger]

Frank Stearns wrote:
> (Don't know WHY this first para got lopped of the first post of this;
> hope it makes it this time; sorry for the extra bandwidth.)
>
> I need to build a few snakes for a location recording operation,
> probably in four or eight channel increments. Interestingly, the
> "best buys" in the Belden line (in terms of cost per foot per pair)
> appear to be eight channel configurations.
>
> I've been looking at several cable samples (the folks at Belden are
> great, BTW), and have come down to a few selections, but am now
> seeking a little wisdom
>
> I can buy Belden AES-EBU cable (1800 and 7890 series) for analog snake
> use, and then also be ready to send digital data down the snake when
> I can afford to put pres and converters on stage. AES-EBU cable is a
> bit more expensive, but now I'm wondering whether I'd ever run
> AES-EBU for long haul data, or whether I'd wind up using something
> else, like the appropriate baluns and a Cat6 snake of some type.

> The AES-EBU cable is 13 pf/ft; the standard analog stuff (1900
> series) is 26 pf. Others have posted that 26 pf/ft should not be an
> audible issue for at least 600 ft. It'd be rare that I'm over 400 ft.
> I also wonder if the higher capacitance might help a little with RF
> immunity (short of going to star quad which, at nearly 40 pf/ft,
> would probably be too reactive at those lengths).

> So, should I lean toward AES-EBU whether I ever send digital or not,
> or stick with the regular analog stuff?

If you are going to send massive amounts of digital in the 21st century, you
are more likely to be using something like an AudioRail, not a massive snake
of SP/DIF or AES/EBU cables.

> The other question is size: for mic runs under, say, 500 ft, do I gain
> much by going to 24 gauge v. 26? That 24 gauge 180x series is big
> stuff; might become a mechanical issue (rolling, transporting, etc).

Resistance of wire per foot

20 .0119
22 .0190
24 .0302
26 .0480

Resistance of wire per 500 foot of 2-conductor cable, or 1,000 feet of wire

20 11.9
22 19.0
24 30.2
26 48.0

Attenuation into 1000 ohm load:

20 0.1 dB
22 0.16 dB
24 0.26 dB
26 0.41 dB

Capacitance per 500 feet of cable

13 pF/ft - 6,500 pf or 0.0065 uF
26 pF/ft - 13,000 pf or 0.013 uF

Frequency of 3 dB Attenuation with 100 ohm source impedance:

13 pF/ft - 6,500 pf or 0.0065 uF F3=244 KHz F1= 48 KHz F0.1=24 KHz
26 pF/ft - 13,000 pf or 0.013 uF F3 = 122 KHz F1 = 24 Khz F0.1 - 12 KHz

IOW, its not going to matter very much what you pick.

[Ben Bradley]

On Fri, 04 Jun 2004 08:29:20 GMT, Stephen Anderson
> wrote:

>Frank Stearns wrote:
>
>> (Don't know WHY this first para got lopped of the first post of this; hope
>> it makes it this time; sorry for the extra bandwidth.)
>>
>> I need to build a few snakes for a location recording operation, probably
>> in four or eight channel increments. Interestingly, the "best buys" in the
>> Belden line (in terms of cost per foot per pair) appear to be eight
>> channel configurations.
>>
>> I've been looking at several cable samples (the folks at Belden are great,
>> BTW), and have come down to a few selections, but am now seeking a little
>> wisdom
>
>I have been doing all installations with AES/EBU compliant cable for
>some time now, for exactly the forward thinking flexibility you
>mentioned. Listening tests, as well as digital measurements, have been
>positive. In the last fixed install I did, we tested 150' runs with no
>signal degradation audible in digital mode.

Do you run digital and analog through different cables in the same
snake? I'd think this could induce noise into an analog signal,
especially a low-level mic signal. If the OP expects to ever run both
digital and analog at the same time, it might be wise to use separate
snakes to keep them separated.
..
-----
http://mindspring.com/~benbradley

[Ben Bradley]

On Fri, 04 Jun 2004 08:29:20 GMT, Stephen Anderson
> wrote:

>Frank Stearns wrote:
>
>> (Don't know WHY this first para got lopped of the first post of this; hope
>> it makes it this time; sorry for the extra bandwidth.)
>>
>> I need to build a few snakes for a location recording operation, probably
>> in four or eight channel increments. Interestingly, the "best buys" in the
>> Belden line (in terms of cost per foot per pair) appear to be eight
>> channel configurations.
>>
>> I've been looking at several cable samples (the folks at Belden are great,
>> BTW), and have come down to a few selections, but am now seeking a little
>> wisdom
>
>I have been doing all installations with AES/EBU compliant cable for
>some time now, for exactly the forward thinking flexibility you
>mentioned. Listening tests, as well as digital measurements, have been
>positive. In the last fixed install I did, we tested 150' runs with no
>signal degradation audible in digital mode.

Do you run digital and analog through different cables in the same
snake? I'd think this could induce noise into an analog signal,
especially a low-level mic signal. If the OP expects to ever run both
digital and analog at the same time, it might be wise to use separate
snakes to keep them separated.
..
-----
http://mindspring.com/~benbradley

[Stephen Anderson]

That's a fair question. So far it hasn't been a problem. I've watched
engineers run various synths, instrument, & line level through the same
multipair as microphones, and no problems have resulted. Most
manufacturers lightly bandwidth limit the inputs of analog gear, either
with RC filtering, or LRC filtering, so the high freq. content of the
AES/EBU is pretty well rejected. Same principle applies to video signals
run near analog wiring.

Keeping in mind that this is pretty common practice in the modern
studio, I think the lower capacitance of AES/EBU would help lower
potential crosstalk between adjacent pairs. Obviously, in a perfect
world, I love to let each signal family have its own trough or tray, but
we can't always get what we want.

Ben Bradley wrote:
> On Fri, 04 Jun 2004 08:29:20 GMT, Stephen Anderson
> > wrote:
>
>
>>Frank Stearns wrote:
>>
>>
>>>(Don't know WHY this first para got lopped of the first post of this; hope
>>>it makes it this time; sorry for the extra bandwidth.)
>>>
>>>I need to build a few snakes for a location recording operation, probably
>>>in four or eight channel increments. Interestingly, the "best buys" in the
>>>Belden line (in terms of cost per foot per pair) appear to be eight
>>>channel configurations.
>>>
>>>I've been looking at several cable samples (the folks at Belden are great,
>>>BTW), and have come down to a few selections, but am now seeking a little
>>>wisdom
>>
>>I have been doing all installations with AES/EBU compliant cable for
>>some time now, for exactly the forward thinking flexibility you
>>mentioned. Listening tests, as well as digital measurements, have been
>>positive. In the last fixed install I did, we tested 150' runs with no
>>signal degradation audible in digital mode.
>
>
> Do you run digital and analog through different cables in the same
> snake? I'd think this could induce noise into an analog signal,
> especially a low-level mic signal. If the OP expects to ever run both
> digital and analog at the same time, it might be wise to use separate
> snakes to keep them separated.
> .
> -----
> http://mindspring.com/~benbradley

--
Stephen Anderson

>~At the end of the day, it's all about
the music >
>

[Stephen Anderson]

That's a fair question. So far it hasn't been a problem. I've watched
engineers run various synths, instrument, & line level through the same
multipair as microphones, and no problems have resulted. Most
manufacturers lightly bandwidth limit the inputs of analog gear, either
with RC filtering, or LRC filtering, so the high freq. content of the
AES/EBU is pretty well rejected. Same principle applies to video signals
run near analog wiring.

Keeping in mind that this is pretty common practice in the modern
studio, I think the lower capacitance of AES/EBU would help lower
potential crosstalk between adjacent pairs. Obviously, in a perfect
world, I love to let each signal family have its own trough or tray, but
we can't always get what we want.

Ben Bradley wrote:
> On Fri, 04 Jun 2004 08:29:20 GMT, Stephen Anderson
> > wrote:
>
>
>>Frank Stearns wrote:
>>
>>
>>>(Don't know WHY this first para got lopped of the first post of this; hope
>>>it makes it this time; sorry for the extra bandwidth.)
>>>
>>>I need to build a few snakes for a location recording operation, probably
>>>in four or eight channel increments. Interestingly, the "best buys" in the
>>>Belden line (in terms of cost per foot per pair) appear to be eight
>>>channel configurations.
>>>
>>>I've been looking at several cable samples (the folks at Belden are great,
>>>BTW), and have come down to a few selections, but am now seeking a little
>>>wisdom
>>
>>I have been doing all installations with AES/EBU compliant cable for
>>some time now, for exactly the forward thinking flexibility you
>>mentioned. Listening tests, as well as digital measurements, have been
>>positive. In the last fixed install I did, we tested 150' runs with no
>>signal degradation audible in digital mode.
>
>
> Do you run digital and analog through different cables in the same
> snake? I'd think this could induce noise into an analog signal,
> especially a low-level mic signal. If the OP expects to ever run both
> digital and analog at the same time, it might be wise to use separate
> snakes to keep them separated.
> .
> -----
> http://mindspring.com/~benbradley

--
Stephen Anderson

>~At the end of the day, it's all about
the music >
>