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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: 89259/89248 twisted pair questions for Jon Risch posted by reagan on February 8, 2007 at 08:37:13:
Q: Should this shielding be adequate for the design?Yes, the need to cut the shield termination down does not adverely affect the shielding action, after all the shield does not carry any signal current, it is operating in 'voltage mode'.
Q: Wouldn't the shielding from a Belden 89248 (or 82248) be as good (or better) than the shielding that I used?
While you can use the shield braid from a coxial cable, rather than use some separately available braid, the shield coverage of the twisted pair may not be optimized. For instance, the Belden 8661 I recommend will cover a spacer filled shield twisted pair without expanding the braid, this allows the little openings between the braided weave to be as small as possible. What we are talking about here is the difference, in shielding coverage percentage. If you "open up" a smaller braid to fit over a larger diameter than it was designed for, these openings get larger, and percentage of shield coverage goes down.
This is not a huge problem, but I always try to maximize my shielding if I am going to bother put one there in the first place.
Q: Have you had any luck with a 89248/89248 (or, in my case 82248/82248) twisted pair?
The larger diameter center wire does invoke a bit of the transient smear that larger diameter wires tend to do. With the original twisted pair design, only one of the wires is a larger one, with both wires being larger, this effect will be larger. Not a show stopper, but another one of those inevitable compromises that creep into cable designs.
Q: Since I have such a large supply of the 82248 cable, what is the best way to use this for a speaker cable design?
As noted in my DIY notes, you can make a multiple conductor speaker cable, weaving three of the cores from 82248 together, and then twisting them around each other, OR, twist two 82248 cores together, and then braid three of these together. The net result is a multi-conductor individually insulated speaker cable with low inductance, and an effective gauge of about 13 1/2 ga.
Braid more pairs together for a lower total effective ga., however, the capacitance will be going up each time you add pairs. The three pair is pretty benign, but adding more, or doubling them will start to get into a range where sensitive power amps could begin to have troubles due to the capacitive loading.
Jon Risch
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Follow Ups
- Re: 89259/89248 twisted pair questions for Jon Risch - Jon Risch 14:13:47 02/10/07 (1)
- Re: 89259/89248 twisted pair questions for Jon Risch - reagan 18:47:05 02/10/07 (0)
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