CAT5 for combined comms & audio

[samchurchill]

Hi,

I've got an "outpost" in the front row for our stage management team that needs a standard belt pack and a TecPro AD903 4-wire interface, both connected to our Clear-com party line system.  As we have a fairly mobile setup, I'm looking into ways of doing this with a single CAT5 cable and some break-out boxes on each end.

Something like this for the CA5 cores:

• 1-3: party line comms
• 4: spare
• 5-6: AD903 input
• 7-8: AD903 output

Do any of you think this is a silly idea, and can come up with something better, or think having those signals running down a single CAT5 together might cause a lot of interference?  Given that the CAT5 has twisted pairs, would it matter which cores I chose to use for each purpose?

Am I right in thinking off-the-shelf CAT5 breakouts aren't appropriate for comms because of the power on the line?

The alternative would be a loom (whether with proper multicore cable or just 3 lots of mic cable in some braided sleeving), but CAT5 just seemed like a good idea as it's plentiful.

Thanks!

[sunray]

1 hour ago, samchurchill said:

Hi,

I've got an "outpost" in the front row for our stage management team that needs a standard belt pack and a TecPro AD903 4-wire interface, both connected to our Clear-com party line system.  As we have a fairly mobile setup, I'm looking into ways of doing this with a single CAT5 cable and some break-out boxes on each end.

Something like this for the CA5 cores:

• 1-3: party line comms 1 & 2 signal etc, 3 ground
• 4-5: AD903 input:
• 6: spare or ground for AD903
• 7-8: AD903 output

Do any of you think this is a silly idea, and can come up with something better, or think having those signals running down a single CAT5 together might cause a lot of interference?  Given that the CAT5 has twisted pairs, would it matter which cores I chose to use for each purpose?

Am I right in thinking off-the-shelf CAT5 breakouts aren't appropriate for comms because of the power on the line?

The alternative would be a loom (whether with proper multicore cable or just 3 lots of mic cable in some braided sleeving), but CAT5 just seemed like a good idea as it's plentiful.

Thanks!

Something like this for the CA5 cores:

• 1-3: party line comms 1 & 2 signal etc, 3 ground
• 4-5: AD903 input:
• 6: spare or ground for AD903
• 7-8: AD903 output

Edited January 16 by sunray

[themadhippy]

Quote

 

1-3: party line comms 1 & 2 signal etc, 3 ground

4-5: AD903 input:

 

problem with that is your splitting different things across different pairs which may lead to future issues.I'd go with the original but  double pin 4 as an earth with 3,or depending on the signal type 1 and 3 as the party signal with 2 and 4 as party earths

[sunray]

1 minute ago, themadhippy said:

problem with that is your splitting different things across different pairs which may lead to future issues.I'd go with the original but  double pin 4 as an earth with 3,or depending on the signal type 1 and 3 as the party signal with 2 and 4 as party earths

My proposal is to avoid splitting signals across pairs.

1&2 orange pair --- party line

4&5 blue pair --- 903 I/p

7&8 brown pair --- 904 o/p

3&6 green pair --- party line ground

[J Pearce]

Party line analogue comms are unbalanced, so using unshielded twisted pair cable may result in noise/hum. Or you may be fine. 

Is the AD903 on a different comms circuit to the pack? If not, could the AD903 be located at the remote end?

[sunray]

2 hours ago, J Pearce said:

Party line analogue comms are unbalanced, so using unshielded twisted pair cable may result in noise/hum. Or you may be fine. 

Is the AD903 on a different comms circuit to the pack? If not, could the AD903 be located at the remote end?

I had access to a single CAT5 between stage and rear of hall in a school hall and due to restrictions on what was permitted it was not easy to run cables.

I knocked up a breakout cable and ran o/p from desk to amp, one microphone and Bluecom. The only problem being the call light on Bluecom added a click on the mic line. I have no idea of the distance as the two lines went to their IT room elsewhere in the school where they were patched together for the event.

[sunray]

3 hours ago, sunray said:

My proposal is to avoid splitting signals across pairs.

1&2 orange pair --- party line

4&5 blue pair --- 903 I/p

7&8 brown pair --- 904 o/p

3&6 green pair --- party line ground

Thinking again :

1&2 orange pair --- party line ground and audio

3 white/green --- party line power.

[samchurchill]

Thanks everyone for your responses - no-one is saying “no”, so it’s probably worth me giving it a go. 
 

13 hours ago, J Pearce said:

Is the AD903 on a different comms circuit to the pack? If not, could the AD903 be located at the remote end?

The AD903 is on the same comms circuit, but I have previously modified it to add a push-to-talk button which affects whether the comms chatter goes to the line output, so it needs to be local.  I guess the other option would be to add a remote for this switch, but that would require far more surgery on the AD903!

[sunray]

I've used cat 5 (or telephone) cable for balanced audio for years, sometimes some very long runs (>1/2 mile for a bandII RSL, studio to transmitter) with very little issue. Often 2 mic lines in and 2 line levels out, I used to have breakout boxes with M&F XLR + Jack*4. The only killer tended to be ground compensated outputs but I never drive a line from them. The circuit which may be the problem is the partyline as JP mentions but I think it's probably more stable than we fear. The only thing to do is try it and see but very important is to ensure its electrically isolated from the other circuits, especially the ground.

[sandall]

7 hours ago, sunray said:

I've used cat 5 (or telephone) cable for balanced audio for years, sometimes some very long runs (>1/2 mile for a bandII RSL, studio to transmitter) with very little issue. 

One of my local churches had been wired with GPO multicore cables (including a remote box to short out individual pairs). Unfortunately the pair colours changed with every junction box, which made chasing dodgy mics a bit of a pain (in the end I just rewired the whole system in FST).

[sunray]

17 hours ago, sandall said:

One of my local churches had been wired with GPO multicore cables (including a remote box to short out individual pairs). Unfortunately the pair colours changed with every junction box, which made chasing dodgy mics a bit of a pain (in the end I just rewired the whole system in FST).

I know the problem very well, the problem is the differing numbers of pairs in each cable as they branch off to  their destination and records.

As a simple example: if a 20 pair cable to a junction box branches out to 5* 4 pair cables, then each of the branches would be identical 4 pair cable with pair 1 starting with blue/white, 

In other words the blue pair of each branch will be pairs 1, 5, 9, 13 & 17 of the original main cable and colour match would sadly be completely impossible.