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Cable Asylum Interconnects, speaker wire, power cords. Ask the Cable Guys. |
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Cable Asylum Interconnects, speaker wire, power cords. Ask the Cable Guys. |
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In Reply to: 100ft Subwoofer cable? posted by FRASERSMITH@HOTMAIL.COM on July 24, 2006 at 09:42:55:
In either case, the sheer length COULD become an issue for the output of the reciever.If it is a line level signal, then it is not uncommon for receivers, etc. to have an output stage consisting of cheap op-amps, and they can barely drive a couple of feet of coaxial cable adequately, and often get into trouble with lengths as short as 10-12 feet, much less 100 feet. It is the sheer amount of capacitance that causes the problems, too hard for the line level output stage to drive.
One solution would be to buffer the line level sub output usng an amplifier, and there are what are known as "distribution amps" that can buffer and drive such a length of cable, since they are designed to do so. However, they are not cheap. Check out such places as Part Expres, MCM, etc, for audio line level distribution amps. You might also find some in a Pro Sound catalog, or a web site catering to Recording Studios, etc.
It might sem that use of a low capacitance coax might work, but since it is a 100 fot length, even a very low C cable such as Belden 89259 at 17.3 pF per foot, would end up with 1,730 pF of capacitance, and this is enough to cause problems with almost ANY grade of op-amp, and most any receiver's line level output. You wouldhave to get the capacitance well below 1,000 pF in order to even have a chance of driving the cable adequately without problems, and this would mean a capacitance of less than 10 pF per foot, a rare commodity in an affordable coaxial cable.
If it is a speaker level output, then again, the sheer length could become an issue for the power amp in receiver, these are often unstable with highly capacitive loads, and the designer's do not expect 100 feet of speaker cable (or coax) to be hung off the amp output.
If it is a speaker level output, avoid coax (unless it is low C, like Belden 8213, and can handle the current too) and use a widely spaced apart zip cord or the largest size (smalest ga. number) you can find.
One of the best in this regard is RS mega-cable, which has the conductors spaced apart MORE than most regular zip cords, and comes in 12 and 14 ga. If you can, get the 12 ga., and this will provide the lowest capacitance load without separating (unziping) the two conductors.
Some of the so-called flat speaker cables intended to be run under carpets, or around the baseboard, that have the two conductors as a flattened braid looking assembly , side by side (NOT sandwiched together on the flat side) with the thin edges edge-to-edge, will also have very low capacitance.
Note that in either case, line level OR speajker level, the sher length could end up acting as an antenna, and you could end up with RFI issues. In this case, a ferrite bead on the line level cable center wire might help, and on the speaker cable, one of the pivoting, locking laminated core rings sold to help filter power cords might do the trick. RS used to sell one of these that should work at speaker cable current levels.
See:
http://www.radioshack.com/sm-snap-together-ferrite-choke-core--pi-2103222.html
and
http://www.radioshack.com/sm-snap-together-toroid-choke-core-2-pack--pi-2103979.html
This latter one would be placed around the cable, and laid against it at either end of the core (sort of kattywhumpus), OR, have some of the speaker wire wrapped around it, and then snapped together.If you can't find any ferrite beads at RS or an electronics parts distributor/store, then line level ferite beads can be purchased from:
http://www.amidoncorp.com/
Amidon Inc. P.O. Box 25867 Santa Ana, CA 92799
Telephone: (714) 850-4660
OLD INFO, SEE WEB SITE FOR CURRENT INFO
Part numbers are:
small ferrite bead, number 75 material, FEB-75B-101, $4.50 pk of 12
medium ferrite bead, number 77 material, FB-77-1024, $2.00 eachGood luck!
Jon Risch
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Follow Ups
- Line Level or Speaker Level? - Jon Risch 07/25/0620:59:02 07/25/06 (1)
- Re: Line Level or Speaker Level? - FRASERSMITH@HOTMAIL.COM 16:24:59 07/26/06 (0)
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