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Old 14th April 2008, 11:30 PM   #21
tilroh is offline tilroh  Australia
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Default cat-5 question(s)

I'm building BIBs for 166Es which will be powered by an Trends Audio T-amp. Input will be a cheap turntable.

From searching these forums it looks like cat-5 is the way to go for speaker wires.

I planned on using two pairs per speaker (use all the wires in the cable).

GM advocates using two wires per speaker. At what length would I need four wires per speaker? Can I simply disconnect half of the wires from the amp for a A-B comparison? Will

How bad is it to leave cat-5 as is, i.e. still in the casing.

My speaker wire run will be about 7mts or 22ft.

It's amazing how many times I can reread posts here and increase my knowledge/confusion.

Thanks everybody.
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Old 15th April 2008, 12:49 AM   #22
chrisb is offline chrisb  Canada
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Quote:
Originally posted by hermanv
You seem to acknowledge that different cables have different sound, even if you didn't like the sound. Is it therefore a leap to guess there might be a cable whose sound you do like?

I agree the process is a PITA, there are many brands and we haven't even touched upon bi-wiring. For me the end result was worth the effort, of course for someone else, their mileage may vary.

In 2 of my 3 current systems, which are presently all Fostex Fullrangers* - CAT5 wire (also as internal speaker wire, and several of the DIY interconnects.) The remaining system (wife's living room) is some generic 20 gauge zip wire, because she couldn't tolerate the blue jacketed CAT5.

*the only loudspeaker XO's in the house are the 2 Logitech computer systems.



tilroh:

I think GM means 2 conductors per speaker : i.e. one of the 4 twisted pairs. Some folks (myself and DaveD included) untwist the conductors, and get pretty funky in separating them with packing tape. In my case, they're spiral wrapped around a length of 3/8" manila rope, and covered with Teflex sleeving (the latter just for cosmetics.
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Old 15th April 2008, 09:24 AM   #23
felixx is offline felixx  Romania
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Old 15th April 2008, 11:17 AM   #24
OzMikeH is offline OzMikeH  Australia
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I had to look up what triboelectric meant... Generating electricity by rubbing certain materials together, Eg: amber and wool, glass and silk.

I work with RF coax cables nearly every day. None of the teflon and silver cables I've encountered are likely to rub, if you've ever tried to strip one you'll see what I mean. even the braid is very tightly laid with a very tight outer sheath. It takes a lot of practice to strip it without nicking the conductors. We use teflon and silver for a few reasons, one of which is the speed of electricity is much higher in teflon and silver cables. about 0.9c compared with about 0.7c (it's called velocity factor and is important with tuned lengths.) Teflon cable is usually double screened as well. Ordinary cheap coax is surprisingly leaky. Another biggie is nickel plated connectors, silver is best. even better than gold. Of course 90% of that has nothing to do with audio, I'm talking hundreds of megaHertz here.

On the other hand I've seen amps built with solid silver wire poked into small teflon tube which is quite loose on the cable. This might cause a problem, but only if it develops charge faster than it self-disharges in moist air. Highly unlikely but not impossible. Simply bending the wire a bit should be enough to hold the tube still.

Tiroh, use a one pair per three metres, If your speakers are three metres from your amp that is one wire for + and one for - and six wires left unused.
Solid core wire tends to fatigue easily. Don't bother with banana plugs, just stick it in the binding post and tighten it with moderate force. Check it is still tight after a week. It will probably break before it corrodes.
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Old 15th April 2008, 11:49 AM   #25
SY is offline SY  United States
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Mike, let me tell you a story...

Some years ago, I wanted to experiment with subtractive crossovers. I built up an op-amp based unit on perfboard using AD712s. The damn thing drove me crazy it was so microphonic. I couldn't seem to localize the components causing the issue. No matter what I tapped, the noise was the same. Mind you, this was a line-level circuit, so the weird subtle effects seen at microvolt levels weren't in play here.

I finally gave up, deciding that either the circuit wasn't stable or the microphonics were due to the perf construction. Either way, total rebuild was needed and I just didn't have the time. It sat in a box for about 20 years, until one day when I read about triboelectric effects. A light went on... The lead-in and lead-out signal cables for that crossover were an ultra-premium Teflon-silver coax, tight braid and all, salvaged out of some surplus RF equipment, where it had worked perfectly. Just for fun, I pulled the crossover board out of storage, hooked it up, and heard the same microphonics. I pulled out the Teflon/silver coax, replaced it with some cheap Radio Shack shielded wire and, yes, the crossover was now quiet. It had been the cable's fault. Nothing was loose at all in the cable's construction, but the triboelectric effect was triggered by the strain in the cable induced by small amounts of vibration or even rubbing against the workbench.

Will this be an issue at speaker level with cables terminated at both ends with a low impedance? Probably not, but I won't say impossible. And I learned about one more non-mysterious way that cables can indeed be audible!
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Old 15th April 2008, 11:57 AM   #26
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Quote:
Originally posted by chrisb
Scott - at your next "meeting of the clans", you should try to spend some time listening for the signatures of different wire/cable types.
Oh I have Chris. It's just that I figure that it's a bit of a hiding to nothing as it's so system dependant.

Re the microphonic issues, I was primarily refering to conditions where the lead is subject to movement or vibration. Due to the relative stiffness of both materials, it's transmitted & you risk some ringing. Not a massive issue for audio as I've said before, but given that it doesn't provide any worthwhile benefits for our purposes, I can't really see the need.
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Old 15th April 2008, 03:01 PM   #27
hermanv is offline hermanv  United States
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Quote:
Originally posted by SY
<snip>
I finally gave up, deciding that either the circuit wasn't stable or the microphonics were due to the perf construction. Either way, total rebuild was needed and I just didn't have the time. It sat in a box for about 20 years, until one day when I read about triboelectric effects. A light went on... The lead-in and lead-out signal cables for that crossover were an ultra-premium Teflon-silver coax, tight braid and all, salvaged out of some surplus RF equipment, where it had worked perfectly. Just for fun, I pulled the crossover board out of storage, hooked it up, and heard the same microphonics. I pulled out the Teflon/silver coax, replaced it with some cheap Radio Shack shielded wire and, yes, the crossover was now quiet. It had been the cable's fault. Nothing was loose at all in the cable's construction, but the triboelectric effect was triggered by the strain in the cable induced by small amounts of vibration or even rubbing against the workbench.
This is most interesting; Teflon and silver foil capacitors are amongst the highest cost capacitors available. They are reported as being very good capacitors. Due to the nature of how capacitors are built there is far more surface area between the silver and the Teflon than in a cable. I suspect that the tension between the silver and the Teflon is also less in a capacitor due to the requirement of not tearing either film during winding.

I'm not disputing your story, I just wonder how the capacitor folks can make a part that is frequently used in crossovers (often a high vibration environment) and get it to work?

My previous RCA interconnect cables were also silver/Teflon, they were expensive and sounded quite good. Here again, the cables were located in a high vibration environment caused by the acoustic output of the nearby speakers.

A mystery.
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Old 15th April 2008, 03:52 PM   #28
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Hmm. Looks like I'm not alone in having some reservations about silver / teflon: http://www.audioholics.com/education...asing-debunked

As always, YMMV though, and it's probably highly dependant upon application. I well remember the best amplifier, bar none, I've never heard. My friend Nick's 300b design, which was superb with the stock valves. We swap in Steve's 300a's and it vanished. Couldn't hear any signiture at all. Shocking. The speaker cable was solid core twin + earth mains, about £0.30 a foot. From that point, it never really occured to me to worry about wire. The speakers? Oh yes: open baffles, Lowther EX4s, supported by twin 12in vitage Goodmans per channel, so the quality of the drivers wasn't really an issue.
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Old 15th April 2008, 04:38 PM   #29
SY is offline SY  United States
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Quote:
I just wonder how the capacitor folks can make a part that is frequently used in crossovers (often a high vibration environment) and get it to work?
I still have some of that wire in case you want to come over and play with it.

Two observations. First, the only really microphonic caps I've run across were ultra-expensive audiophile ones. The source for them swore that they'd increase the "bloom" and "sounstage." Probably would, too, adding that subtle hint of reverb.

Second, the foil and film are wound in a cap (I think that's the source of the microphonics, the less-than-stellar winding tightness of fashion caps), wheras in cables, the Teflon is extruded onto the wire. I'd expect the interface to be quite different.
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Old 15th April 2008, 04:47 PM   #30
hermanv is offline hermanv  United States
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Quote:
Originally posted by SY


I still have some of that wire in case you want to come over and play with it.

Two observations. First, the only really microphonic caps I've run across were ultra-expensive audiophile ones. The source for them swore that they'd increase the "bloom" and "sounstage." Probably would, too, adding that subtle hint of reverb.

Second, the foil and film are wound in a cap (I think that's the source of the microphonics, the less-than-stellar winding tightness of fashion caps), wheras in cables, the Teflon is extruded onto the wire. I'd expect the interface to be quite different.
I am most curious about the wire and hoped someone had experience or an observation as to what is going on.

I agree fully about winding tension, specialty capacitors are often made by boutique shops in low volumes, quality control and repeatability are probably a problem. I have used film and foil (not the silver/Teflon. can't afford them) without difficulty in crossovers.

I live in Santa Rosa, not that far from Napa, only sheer laziness prevents me from taking advantage of your generous offer.
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