Hum - Both Ground Loop / Electrical interference

[mwigtkm]

Okay so maybe I was crazy, but here's the deal. When I bought my house, it had about 32 ethernet drops (in my relatively small ranch home) so of course that sold me on the house!

What the heck does this all have to do with Xlobby and Ground loops. Well I had all of these "extra" ethernet ports in my living room and rec room that I started to wonder if I could use it to pass the signal coming from my soundcards in my xlobby server.

I found several websites that talked about using solder on RCA's onto Cat 5e cables to send the signal, so I bought the "stuff" and soldered on the connectors onto two patch cables and waaaalllla. I had a connection from my basement server upto my living room receiver. 1 problem though. The Hum.

There is actually two causes of this hum. 1. Electrical Interference in the walls. Even if I only have the patch cable hooked up to the receiver to that ethernet port and the other end (in the basement) not hooked up to the computer there is a slight hum. 2. Sound card. When I hook up the sound card, the Hum becomes considerably louder.

My question becomes, would a ground loop isolator like this:

http://www.radioshack.com/product/index ... age=search

fix my problem? or at least make it considerably better? Other Ideas?

[Jay]

a, you're sending line-level, not speaker-level audio? Seems so.
b, assuming line-level, is your cat 5 shielded?
Cat 5 is 120 ohms and line-level audio is 600, if I recall right. However, I use 100 ft runs of shielded cat 5 for property audio and video - and both are great, despite the impedance miss-match.

If you go to the Shack, I believe you can get a refund if it doesn't work.

Take a look here> http://www.epanorama.net/documents/grou ... lving.html

[mwigtkm]

To be honest, I couldn't tell you what is run in the walls other than it is Cat 5e (I asked, because I wanted to be able to do gigabit networking) and I can run at gigabit speeds no problem. My guess is that there is probably some considerable crossing of electrical wires in the walls (I believe that has to be a part of the problem considering that I get a hum regardless if it is plugged into the back of the computer or not).

It is funny you should mention that website, as that is where I found the recommendation of the RadioShack part! My current thought is to pick one up and place it between the ethernet jack in the wall and the receiver to hopefully get the maximum reduction in noise.

EDIT: Dang, unshielded. hmmm....Well guess I will see if that little device does it or else I am going to have to rethink how to wire everything!

[Jay]

keep us posted.

[Marbles_00]

I don't think Line Level is 600ohm impedence. You might be thinking about PA systems. I think they are 600 ohms. Line level, you want as little resistance and as little capacitance as possible.

mwigtkm,
You can certainly try the device from Radio Shack...it's pretty cheap.

OR

Have you thought about using a balanced line driver/reciever circuit. AudioControl (http://www.audiocontrol.com) have the BLD-10 (Balanced Line Driver) and the BLR-10 (Reciever) that were made for Cat5 cable. Or if your cheap like me ( ) and like to build, you can use this circuit found here:
http://sound.westhost.com/project51.htm
and build your own.

You can google to find out the advantages of running balanced signals as opposed to unbalanced signals.

Hope this was helpful.

[Jay]

I don't think Line Level is 600ohm impedence. You might be thinking about PA systems. I think they are 600 ohms.

I stand corrected. dynamic mics are typically 300 -600 ohms impedance and line level is 10K ohms impedance.

When we say just "ohms", we're usually talking DC resistance. When we say, "impedance", we're talking about AC - which is audio in this case.

</soap>

Anyway Marbles, that's cool; I didn't know about audio adapters for Cat 5. Very useful info!

[Marbles_00]

You have to remember too that the 10K ohm is not in the cable but is usually in the source output. Most times you want a matching circuit on the resulting input side as well to take care of reflections. This is one primary reason why you want to have a line level cable with as little capacitance as possible, at different frequencies, the impedence changes, causing the overall impedence to change, which causes reflections in the lines and frequency attenuation which may become audible (depending on the capacitive reactance).

Could go into greater detail and be way more elaborate, but that is it for todays lesson.

[Jay]

Oh, I agree. I think this just a semantics thing. Anyway, let's just hope RS comes thru for the man

[Marbles_00]

Yeah, the RS option is cheaper (than AudioControl), and easier (already built).

[mwigtkm]

It is amazing how helpful this forum can be. I haven't had a chance to hit radioshack (hoping tonight) as I had dinner with a friend who is moving out of town this weekend. My thoughts are is that if I can fix my problem for 17 bucks then awesome! I will let you know what I find out once I get my hands on one!

[mwigtkm]

It WORKS!!!

I have my patch cable connected to my server's soundcard in the basement that runs to the my patch panel next to the server. That runs upto my living room upstairs to the ethernet port in the wall. Then I have my patch cable with the Audio RCA's attached to it. Then I put a couple of inline RCA couplers and then the Ground Loop Isolator between the couplers and the receiver. No hum!! It took care of both the ground loop and the electrical interference (the package actually says it will do both).

Thank you all for your help!!

[Jay]

Excellent! Congrats