question for audio experts

gush

gush

Where is that speedo pic
Joined
Nov 4, 2012
Messages
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Location
washington iowa
I'm helping with a sound system install for some friends of mine at a country club. They want to patch TV's to the in house system. My question is how far can you run the stereo audio RCA without boosting signal?

Thanks
 
I typically don't recommend running unbalanced signals longer than 30ft or so. Ultimately it depends on the source and destination components, quality of cabling, and the actual environment. An unbalanced line will act like an antenna for outside interference. So a line picking up buzzes and hums in a busy city with lots of RF flying around (radio stations, emergency vehicles) may be dead quiet if used in a residential neighborhood in the suburbs.

If you need to run longer than that, run the signal into a stereo DI (or two mono DI's to make a stereo pair) and run XLR cables into mic inputs on the board. Then you can run hundreds of feet with no signal loss or chance of interference.
 
Also keep them away and do not run parallel to power cables. Definite noise microphones. If you have to cross power, di it a 45 degree angle to keep the noise down.
 
I have been looking at converters to go to cat 5 wire but looks like 2 converters for each of the three TVs. Would like a cheaper method.
 
gush said:
Is there a DI box that will take L/R RCA and make a mono XLR?
Click to expand...

Not that I'm aware of, but entirely possible. The Radial JPC does take a stereo set of RCA's.

You can just use one DI and use an RCA Y-cable to single TS mono. You wouldn't want TRS on the 1/4", that's not what the DI box is expecting. But using the proper Y you are summing L R both to the tip, as opposed to keeping them seperated on tip and ring.

Edit: Of course some say just plug L and R TS jacks into both 1/4" jacks of the DI, and they say it sums them to mono. And that makes sense, because really those jacks are wired together so you can pass thru to an amplifer or anything else. However, and maybe I'll go and confirm this again today, last time I tried doing that it seemed like what presented at the XLR out would only be one or the other, not both.
 
Last edited:
You can also use RG 6 cable with RCA ends soldered or pressed on for longer runs. I use it for both audio and video with good results.
 
I appreciate the advise tremendously. I will check out the RG 6 cable.

I do like the idea of combining LR signals with a DI box and finishing the run with XLR. The sound system won't be configured in true stereo anyway and a single board channel foreach TV would make it simple for anybody that needs to control it.
 
I just tried running a stereo pair of 1/4" jacks into a DI and they did sum together. However with much less output than one being used alone over the other. This is probably due to the impedence change when running two lines instead of one. The current seems to drop considerably. So it will give you a summed output but will probably end up with a much higher noise floor. It still should be ok for most applications, and technically running a Y cable like I mentioned earlier would have the same effect.
 
G-Man said:
Also keep them away and do not run parallel to power cables. Definite noise microphones. If you have to cross power, di it a 45 degree angle to keep the noise down.
Click to expand...

Actually the recommendations are to keep low voltage runs (data, phone, video, line level audio, amplified audio) 3 feet away from power lines such as AC and only cross at ninety degree angles.
 
good point. I probably should have said at least 45 degrees with 90 being optimal.

Also there is some really good RG6 out there that is silver core vs. copper that I have used which is really good, very quiet but super expensive by the foot.
 
I'm intrigued by this RG6 suggestion. It looks like what would typically be used for cable lines carrying video and audio. How is it more ideal than conventional RCA cabling? Better shielding? How about impedence concerns? Will it operate in a similar way? I know a conductor is a conductor, but you just terminate with RCA plugs and it will interface properly?
 
RG6/U is double-shielded with lower capacitance per foot than a guitar cable, so unbalanced audio can travel father without noise or attenuation problems. How far depends on your environment and audio equipment, maybe 25-50 feet max. One way to extend unbalanced cabling is drive it with a good buffer. Anything longer should use balanced cables with DI boxes.

Unbalanced audio connections are not impedance-matched, because the audio equipment does not conform to one standard. Terminating to RCA is OK, it's a "whatever works" world.
 
I would recommend something from MuxLab such as this - http://muxlab.com/products/category/audio-video/stereo-hi-fi-balun-2-pack . The benefit here is because it is twisted pairs, you can run closer than you normally would to bad RF sources and not pick up as much, if any, noise to the signal. You will also be able to long distances without as much loss.

MuxLab has a lot of cool little boxes to fit a lot of needs for decent prices. I've used a lot of these over the years and they just plain work. They also have a great lifespan (they don't fail very often at all).

If you want to look at something a bit more sophisticated, check out the Stick-On line from Radio Design Labs. All sorts of mixers, BALUNS, amps, and more for a decent price.

BTW, in many environments like this, the owners of the place tend to go with an A/V matrix switch that can route audio & video to any TV from whatever source. Autopatch and Knox Video Technologies are the two I have the most experience with (we use them in a very different way however) but both run very well. More money than what your budget probably is, but worth looking into on EBay.

Good luck with what sounds to be a pretty cool little project!
 
Thanks for all the excellent advice! I will keep this info for future use.

This project has been frustrating. The people that asked me to help are people that have hired me for several sound jobs in the past so I wanted to help. After researching solutions for their requests the financial people have vetoed all the cool features that I designed into the system. Now it will be a simple system. Cost has become top concern where it wasn't before.

That's how it goes! I gained more useful information on this site than anywhere else which is one more reason to love this forum. Thanks all.
 
G-Man said:
Also keep them away and do not run parallel to power cables. Definite noise microphones. If you have to cross power, di it a 45 degree angle to keep the noise down.
Click to expand...

Regular cables don't be run parallel either for best results.
 
I've used RG6 for a lot of different applications with great results. I always use it for subwoofer cables, especially for longer runs. I've used it for video cables up to 30 feet with no real degradation in quality, for a very odd placement issue with my Apple TV box, I use it to run audio back to my surround sound receiver which is about 25 feet with no falloff. The weirdest thing I've used it for is speaker wire. Musical Interface Technologies (MIT) sells a RCA to speaker wire converter allowing you to run shielded cable for speaker wire as long as you have the correct terminations at both ends. Works well for longer runs.
 
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