Send Audio Signal Longer Distance

[Suraj143]

I have a CCTV microphone unit & its audio output is a RCA out (Line out) Output Level is (0-6Vpp).I want this audio to be delivered to a DVR Audio IN which is placed over 80m.Now I have wired a coaxial cable RG59 & there is so much humn/noise.

How to send "Lineout audio signal" over longer distance?

 

[ronsimpson]

You have hum and noise on the shield of the coax.
Search for "audio isolation transformer balanced unbalanced".
There are little boxes that on the receiving end may remove the hum. "balanced to unbalanced"
If that alone does not work then you may need the opposite on the end of the cable.

Audio cable for long runs: Note two shielded wires.

For long distance audio we use a coax with two wires inside the shield. The first transformer takes the "audio" & "ground" in and makes Ground, Audio & Not_Audio. (signal and the inverted signal) On the receiving end noise is on all three wires. The transformer takes the Signal & Inverted Signal and substrates them to get 2xSignal with out noise. The noise on the black wire and noise on the white wire are also substracted and = "0"

 

[Neilf]

Just search for Stereo RCA to Stereo RCA Audio Extender Over Cat5/6 Cable

 

[audioguru]

I think the microphone preamp has a balanced output signal plus a grounded shield but your TV cable has only one unbalanced wire inside its shield.
Microphone cables usually have two wires inside its grounded shield.

 

[Nigel Goodwin]

80m line level audio using unbalanced cable shouldn't be an issue? - I suspect his problem is that he's using RF coax and not audio coax, with RF coax not providing much screening at all at audio frequencies.

 

[Beau Schwabe]

About 20 years ago, I used the method posted in #2 to run under the crawl space of my house to go from the bedroom (PC where sound was originating) to the living room (where the Stereo system was). About 100 feet without any detectable noise.... Although I didn't use COAX, I just used two audio isolation transformers wired back to back over a distance for each channel with standard Phono cables. ie. for each LEFT and RIGHT channel : LINE-OUT from PC to transformer on one end ... on the other end transformer to AUX-IN on the Stereo system with just twisted pair wire in between the transformers ... no shielding.

 

[audioguru]

Yeah, I have never tried TV coax cable for audio signals. I have always used audio cables for audio but some cables had a very poor shield.

 

[Suraj143]

Many Thanks for the information. I got delayed to reply. Sorry On that.

Yes I already used a RF coax (RG59) to deliver audio.

As Ronsimpson's diagram what type of audio transformer do I have to use?There are 600:600 ones, Some are 600:2K ones...etc.Not sure what to buy?

6.84US $ 5% OFF|600ω: 2k4 Permalloy Audio Isolation Transformer Audio Signal Isolation Transformer Pt-10 - Transformers - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

 

[schmitt trigger]

If your audio source can drive a 600 ohm impedance, those should work fine.

 

[audioguru]

A transformer provides a balanced signal but your coax cable is unbalanced.

 

[crutschow]

A transformer provides a balanced signal but your coax cable is unbalanced.

If you ground one side of the transformer output and ignore the center-tap, then it will be a single-ended unbalanced output, which should drive the coax fine, especially at audio frequencies.

 

[Nigel Goodwin]

If you ground one side of the transformer output and ignore the center-tap, then it will be a single-ended unbalanced output, which should drive the coax fine, especially at audio frequencies.

And what does that achieve? - the existing line output will already drive the coax fine.

The issue here (as I see it) is that he's not using audio screened cable, adding transformers isn't going to make any difference while he's still using unsuitable cable.

 

[rjenkinsgb]

have a CCTV microphone unit & its audio output is a RCA out (Line out) Output Level is (0-6Vpp).I want this audio to be delivered to a DVR Audio IN which is placed over 80m.Now I have wired a coaxial cable RG59 & there is so much humn/noise.

Is the audio (at the recorder or amp end) in any way at all cross-connected with the camera power or video connections - eg. do they go to the same DVR?

If there is any connection it may well just be a ground loop, where the audio screen is also acting as a power or video ground return and having other signal superimposed.

If that's the case, all it should need is a 1:1 transformer at the receiving end to break the loop.

 

[crutschow]

And what does that achieve?

At audio frequencies likely nothing
I was just answering AG's comment about the transformer output being balanced, not unbalanced (single-ended).

 

[Suraj143]

Is the audio (at the recorder or amp end) in any way at all cross-connected with the camera power or video connections - eg. do they go to the same DVR?

If there is any connection it may well just be a ground loop, where the audio screen is also acting as a power or video ground return and having other signal superimposed.

If that's the case, all it should need is a 1:1 transformer at the receiving end to break the loop.

YOu are right. All the devices got the same DVR unit (Cameras, MIC signal etc..)Please see my drawing.

 

[rjenkinsgb]

A 1:1 audio transformer in line with the mic input at the recorder, should get rid of the problem.

You can buy built units cheaply on ebay, eg.

Pardon our interruption...

Or, the line transformer from a scrap dial-up 56K modem will work very well for general (though probably not HiFi) audio isolation - I've used those for years, until they became hard to get.

 

[unclejed613]

Now I have wired a coaxial cable RG59 & there is so much humn/noise.

are both ends of the shield connected properly? a lot of 75 ohm cable has aluminum shield wires, which don't solder well (or at all). try something with copper shield wires instead.

 

[audioguru]

You are using a video cable that always has video connectors attached to the foil at each end. I think your video foil shield is not connected at each end.
Some audio cables also have foil but also have a stranded copper wire running along touching the foil for connections of the shield at each end.

 

[Suraj143]

Or, the line transformer from a scrap dial-up 56K modem will work very well for general (though probably not HiFi) audio isolation - I've used those for years, until they became hard to get.

Very Nice Idea. I found this transformer from a telecom PCB board. I measured its resistance from a multimeter. Will it suits for my job?

 

[rjenkinsgb]

As long as it is a line transformer it should be fine. Try it using the outer pins on each side.