Advice on choice of Audio Cable

Fozzie Bear

Fozzie Bear

n3wb
Nov 21, 2019
19
9
East Hertfordshire UK
I am about to install an Exvist 8.0Mp POE CCTV camera in our village hall to stream meeting to Youtube via RTMP protocol. I need to run a long audio cable from the microphone amplifier at the front of the hall to the camera at the other end as an audio feed and trying to decide on the best cable. I have looked at various cable types including pre-made with included 3.5mm jacks on each end to rolls of cable. The lead will run in some large timber boxing down the side of the room and will be adjacent data and mains cable so it really needs to be screened to reduce any pickup. I am looking on the well known auction site and equally well known large online retailer and there are various versions:-
In each case one end will be terminated in a 3.5mm stereo jack to go into the camera and a 6.3mm jack or XLR plug
Trying to keep the price of install as low as possible but don't want problems with hum or pickup on audio so any advice would be appreciated.
 
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looney2ns said:
Keep the cable at least 12" away from any mains cables, or you will very likely have problems.
I'd stick with good Belden audio cable.
My 2 cents.
Click to expand...
Many thanks,
Keeping at least 1ft away is going to be difficult as I have got to install in the same 6"x6" boxing down the length of the hall. Hence my question about best cable/shielding.
I am aware of Belden but they make Digital Audio, Analogue Audio and Microphone cable. Which do I choose between analogue audio and Microphone?
 
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Other option would be to enclose the cable in metal conduit, that would add additional shielding, and most likely prevent any problems.
Be sure to ground the conduit at one end.
Analogue Audio would suffice.
 
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If that 6x6 "boxing" is also carrying power conductors I'd suggest checking your local electrical codes as putting LV wiring in the same wire way as high voltage wiring is usually a code violation. Given the location it would seem important to remain in code.
 
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FYI -

For a section I needed to squeeze data cable ( cat5e/6 ) near electrical I used a section of EMT .. worked very well for me ..
 
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sebastiantombs
Many thanks for your reply. In the UK we use IET and IEE 17th/18th Edition Regulations. In summary they state that either SELV (Data) cables and LV (230v mains voltage) should be physically separated e.g. dado trunking that has multiple compartments. Or the SELV cable must have the same insulation specification as the LV cables.
In my scenario I could just lay the data cables on the other side of the boxing to the mains cables as the insulation specifications are the same but I have chosen to install both the Cat5E and final audio cable in flexible plastic conduit which will satisfy both the insulation and separation requirements.

However my original question, which so far has only been addresses by looney2ns, is the specification of the audio cable to avoid as much hum and interference as possible. Plastic flexible conduit will not have any effect on this so my thinking was to go for double screened cable but which of the types I have linked to as the double screened mic cables have smaller conductor cross section. The audio out from the mic amp will I assume be between 0.5 and 1.0v unlike a microphone which is in millivolts. so the voltage drop over 25m should not be that great?
mat200 Sorry what is EMT? Extruded metal trunking??? If so that is not suitable in my scenario due to several changes in direction in the boxing, hence flexible conduit.
 
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EMT is Electrical Metallic Tubing - aka cheap, thin conduit. Should not be used where exposed to things running into it like a wheeled cart. In commercial design, we only used EMT where completely protected, like behind walls. Unfortunately, short of putting the LV cables in a grounded, metal conduit, you can't be sure that you won't have interference. It doesn't happen every time, but it could. I suspect that good, brand name, shielded or double shielded cable would avoid any interference. But, it is very hard to say. In certain cases you also get ground loops, very low current running through shielding which introduces interference. Rare, but it does happen.
 
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Cheaper, easier & better solution - will prevent any hum or interference:
Use CAT6 balens to extend Audio signals. Many venders make these, I prefer RDL, they have extenders for balanced & unbalanced audio, passive & active Tx & Rx.
 
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Thank you all for your help and suggestions. I will consider them all before deciding on a final solution.
One final question however. Do you know if the audio in to IP cams is mono or stereo? I can find anything on the spec of the camera have bought which states one or the other.
 
The cam specs call out a 3.5mm jack, but doesn't specify if TS, TRS or TRSS (Tip, Ring, Sleeve).
Typically it's TRS.
 
I have only seen two wires for the microphones on my test 38 mm camera boards with Hikvision firmware.

About 5-6 years ago did a Russound distributed audio system in an office and used cat5-6e baluns to bring one audio input from the front of the office to the rear communications closet. (~75 feet or so). Worked fine.
 
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