Long RCA Cable help

[Mr._Clark]

If you want a real world example of how NOT to do it, here’s what I did: I ran two 14 gauge unshielded speaker wires from my AVR up inside the front wall, through the attic, and back down inside the rear wall. The lines are about 12 feet apart in the rear wall and connect to a pair of SVS NSD-12s.

One of the lines in the rear wall runs parallel to a power line in the same space between a pair of studs. This results in a very noticeable 60 Hz hum from that sub. I have not noticed any issues with the other sub. My hearing is not especially good, so it’s possible there’s some relatively minor funky stuff going on that I’m missing.

Based on my extremely limited data set, power lines are the natural enemy of speaker cables (at least if run in parallel near each other). I don’t know if shielded cable alone would solve the problem, but I have no intention of finding out. When I do get around to fixing it, I’m going to use shielded cable and run it well away from the power lines.

It might be interesting to experiment with a long extension cord and shielded vs unshielded cable to see how much difference it actually makes.

 

[Pedro Alvarado]

APORTO

is moving things around an option? you could move the couch to the stairs wall and the screen to the window wall.

you could run al wires along the wall that the screen is at now and not bother routing wires over the doorway.

 

[highfigh]

If you want a real world example of how NOT to do it, here’s what I did: I ran two 14 gauge unshielded speaker wires from my AVR up inside the front wall, through the attic, and back down inside the rear wall. The lines are about 12 feet apart in the rear wall and connect to a pair of SVS NSD-12s.

One of the lines in the rear wall runs parallel to a power line in the same space between a pair of studs. This results in a very noticeable 60 Hz hum from that sub. I have not noticed any issues with the other sub. My hearing is not especially good, so it’s possible there’s some relatively minor funky stuff going on that I’m missing.

Based on my extremely limited data set, power lines are the natural enemy of speaker cables (at least if run in parallel near each other). I don’t know if shielded cable alone would solve the problem, but I have no intention of finding out. When I do get around to fixing it, I’m going to use shielded cable and run it well away from the power lines.

It might be interesting to experiment with a long extension cord and shielded vs unshielded cable to see how much difference it actually makes.

Running ANY cable next to and parallel to power wires is a bad plan- the magnetic field couples to the audio cables and you hear hum. As the current in the power lines increases, the interference becomes stronger. If the cables must be near each other, the minimum distance that's usually recommended is 16". If they must cross, do it at a right angle.

 

[BMXTRIX]

Running ANY cable next to and parallel to power wires is a bad plan- the magnetic field couples to the audio cables and you hear hum. As the current in the power lines increases, the interference becomes stronger. If the cables must be near each other, the minimum distance that's usually recommended is 16". If they must cross, do it at a right angle.

The bigger issue is running a speaker cable designed for speaker level voltage instead of a shielded or balanced cable designed to carry a low-voltage signal. Still, you are spot on about power being a top killer of audio quality. I can say that over the years I've never picked up an audible hum from running coax to a sub. But, I have seen it from running analog video cabling. Going digital completely fixed any video issues.
I have never had a 60hz hum in speakers from well designed amplifiers. I have had a number of amps that have introduced noise into the system, and it always pisses me off because I never know ahead of time that the amp is going to do that. I like leaving amps on all the time in distributed audio systems so that they start playing instantly. A good amp has NO hum when there is no signal running to them. A poorly designed amp will have a hum in the speakers when there is no signal running through them. Lifting ground sometimes helps/fixes the issue, but not always. I love my Rotel amps.

 

[highfigh]

The bigger issue is running a speaker cable designed for speaker level voltage instead of a shielded or balanced cable designed to carry a low-voltage signal. Still, you are spot on about power being a top killer of audio quality. I can say that over the years I've never picked up an audible hum from running coax to a sub. But, I have seen it from running analog video cabling. Going digital completely fixed any video issues.
I have never had a 60hz hum in speakers from well designed amplifiers. I have had a number of amps that have introduced noise into the system, and it always pisses me off because I never know ahead of time that the amp is going to do that. I like leaving amps on all the time in distributed audio systems so that they start playing instantly. A good amp has NO hum when there is no signal running to them. A poorly designed amp will have a hum in the speakers when there is no signal running through them. Lifting ground sometimes helps/fixes the issue, but not always. I love my Rotel amps.

The hum form an amp that has no input or the input jacks are shorted aside (usually from power supply problems), the main cause of hum is ground loops but with cheap light dimmers, all bets are off. The ground loop isn't from a poor amp design, it's from the electrical service. That said, it's not that hard to eliminate the hum with an isolation transformer but it's good to be careful when lifting the ground- that removes the safety of the connection and makes it possible to have an electrically 'hot' chassis.