Cat5 as Audio Cable - AVS Forum
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post #1 of 10 Old 02-04-2009, 01:36 PM - Thread Starter
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Hey everyone. I spliced connectors from RCA stereo cable onto a cat5 cable that runs from my basement to my bedroom (roughly a 140 foot run), into two sets of audio cable - one pair goes to a satellite receiver, the other to a dvd player. On the receiver at the other end, the inputs are Video 2 and Video 3.

Everything is working great - the sound is actually quite good. The receiver is being used as a whole house distrubutor to six different zones through a niles audio speaker connecting block, and all of the volume controls in the six zones are impedance matched.

The only problem I'm having is that when the Video 3 input is selected for the DVD player, and the DVD player is off, if I turn the volume control all the way up, I hear faint sound from the satellite receiver (the Video 2 input). Similarly, if the Video 2 input is selected and the satellite receiver is off, I can turn the volume control up all the way and the DVD player can be heard very faintly. As long as the component that matches the input is being played, sound is fine (i.e. selecting Video 2 if the satellite receiver is on provides good sound with no feedback or distortion).

My question, is this slight bleeding normal because I'm using one cat 5 cable for both sources, even though I'm of course using different pairs for the different inputs? Or could the issue be with the circuitry of the receiver? I'm fairly certain I don't have any crossed or touching wires, and everything is wrapped in electrical tape. If I'm not doing any damage to anything, I don't really care because as long as I'm listening to the source for the selected input, everything is ok.

Thanks.

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post #2 of 10 Old 02-05-2009, 09:22 AM
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Temporally move the receiver back to the room with the other equipment, hook everything up with short co-ax cables and try it that way. Lots of receivers and pre-amps have input signal leakage.

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post #3 of 10 Old 02-05-2009, 12:45 PM
 
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It's called crosstalk, due to inductive coupling.
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post #4 of 10 Old 02-05-2009, 05:30 PM - Thread Starter
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Quote:
Originally Posted by Speedskater View Post

Temporally move the receiver back to the room with the other equipment, hook everything up with short co-ax cables and try it that way. Lots of receivers and pre-amps have input signal leakage.

Pretty much impossible because the speaker connections are in the basement. The run is basement to master bedroom on the second floor. The speakers are controlled by a volume control in the master bedroom, which is one of six zones. The outputs of the amplifier section (to be completely accurate, it's the zone 2 amplifier section) on the receiver go into a niles speaker connecting block, and from there I have seven sets of speaker cable going to seven different zones in the house. So in reality, with this setup, I'm providing very little power to each zone since my volume controls are set at 8x impedance - but it still gets plenty loud enough for me.

I'm not concerned about the bleeding from a sound quality perspective because it's really an either/or setup - I'm either watching the satellite box or a DVD, really wouldn't be outputting audio from both at once, and even if I did, it's not audible if the source selected is outputting sound. The only time I hear bleed is if I have the source selected to the DVD player and the sat box is on, or vice versa, and even then I'd have to have the volume control turned all the way up to hear any faint sound.

My only concern is am I doing any damage, or risking shorting anything out? If not, it's nothing that will have an impact on the setup.

Thanks.

Quote:
Originally Posted by duvetyne View Post

It's called crosstalk, due to inductive coupling.

That goes way over my non-technical knowledge . Is inductive coupling a problem? I assume that since all of the cat5 wires are enclosed in one sheath, that's what your talking about? Again, as I mentioned above, as long as it's not hurting anything, I'm ok with it.

Thank you both for your assistance!

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post #5 of 10 Old 02-06-2009, 04:08 AM
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The impedance of the line level audio circuit is probably too high for it to be inductive coupling. That leaves capacitive coupling and simply replacing the cat5 with standard audio cables would fix the issue since they have adaquate shields for audio. It's not going to hurt anything and if doesn't bother you at that level leave it.
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post #6 of 10 Old 02-06-2009, 01:16 PM - Thread Starter
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Originally Posted by NightHawk View Post

The impedance of the line level audio circuit is probably too high for it to be inductive coupling. That leaves capacitive coupling and simply replacing the cat5 with standard audio cables would fix the issue since they have adaquate shields for audio. It's not going to hurt anything and if doesn't bother you at that level leave it.

Thank you. It certainly doesn't bother me - particularly since there is no reason to have both components on at once.

I realize standard RCA cables would be the best way to wire, but it costs a heck of a lot more for 140 feet of RCA stereo cable than it does for 140 feet of Cat5. I have 4 different Cat5 runs from the basement to the TV (in addition to the 2 coax runs for sat. TV). In theory, I could just use a different Cat5 cable as well, but it was so easy just to splice everything to one cable and save the other there for future use.

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post #7 of 10 Old 02-06-2009, 08:41 PM
 
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You could try analog audio balun instead which can help with this, check ETS for eg. Not because you need a 'balun' per se for analog audio, but for over cat5 it helps for this reason precisely, because everything bleeds right into the line since it's not shielded and not balanced if you just splice on there.
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post #8 of 10 Old 02-09-2009, 01:59 PM - Thread Starter
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Quote:
Originally Posted by ChrisWiggles View Post

You could try analog audio balun instead which can help with this, check ETS for eg. Not because you need a 'balun' per se for analog audio, but for over cat5 it helps for this reason precisely, because everything bleeds right into the line since it's not shielded and not balanced if you just splice on there.

Even with a balun, though, I'd need two separate cat5 cables, right? Right now I'm using one cable spliced to 2 sets of RCA connectors, saving the other cat5 cables in the wall for the future. So I can see the lack of shielding could probably cause some bleed, but I'm willing to live with it since I can't envision a situation where I'd have both the sat receiver and dvd player playing audio at the same time (and even if I did, it wouldn't be noticable as long as the selected sources was distributing a signal). As long as I'm not damaging my system somewhere, I'm ok with where it is. I actually can't believe how good the sound is (relatively speeking, of course) using 140 feet of cat5 cable as audio connectors.

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post #9 of 10 Old 02-09-2009, 02:23 PM
 
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Quote:


I'd need two separate cat5 cables, right?

Why? How many audio channels are you transmitting?
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post #10 of 10 Old 02-09-2009, 02:42 PM
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Quote:
Originally Posted by tjk View Post

Even with a balun, though, I'd need two separate cat5 cables, right?

A quick Google search turned up two audio baluns for cat5 that carry 4 channels of audio ( see http://www.lashen.com/vendors/intelix/audio-cat5.asp, fourth unit down, or http://www.proaudio.com/product_info...oducts_id=3106). There are probably other manufacturers of such units also. That should significantly reduce your crosstalk.

But of course the cost of those may negate the cost advantage of using cat5 instead of audio cable.

So if the crosstalk bleed is not a problem then just leave it the way it is.

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