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Old 21st November 2014, 04:33 AM   #1
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Default Twisted wires

Hello All,

I am about ready to wire my new tone arm. I know about twisting the wires of each stereo channel but I don't know what to do with the twisted pairs. Should they be twisted with each other or should they be just randomly bundled inside the tone arm tube?
what is the rate of twist? Is it critical? Should it be loose or tight?
Your help is greatly appreciated.

Sincerely,

Ralf

Last edited by Straight Tracker; 21st November 2014 at 04:35 AM. Reason: Grammar
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Old 21st November 2014, 07:51 AM   #2
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A twisted pair rejects interference by presenting a "loop area" to outside interference fields that is small and also changes polarity very often. The loop area, which determines the coupling between interference fields and the pair of wires, is the sum of multiple tiny loops (each twist), that tend to cancel each other because they alternate polarity.

In a tone arm, the cartridge presents two coils, and ideally, each coil will be connected to the preamp with a twisted pair to reject interference. The two twisted pairs can be put into the tone arm tube somewhat randomly, because the nature of each twisted pair alone is the important part. Coupling between the twisted pairs is possible, but again, with tightly twisted pairs and a small difference in twist pitch between pairs, crosstalk will also be rejected by each pair. (This is how the phone company was able to put a bunch of pairs into a single small jacket and prevent crosstalk between phone lines a long time ago.)

A "good" twisted pair should have regular, tight, and uniform twists to reject outside interference. If a twisted pair has more twists per length, then it can reject interference better, even if the interference source is close to the pair. The twisting cancels the interference because the interference, whose strength decreases with distance, will influence several loops in the twist, and each loop has an opposite polarity. So, more twists per length allows the pair to reject interference sources that are closer to the pair. The uniformity of the twists is what determines the interference rejection, but it's nice for crosstalk reduction to use one twist pitch for the left channel pair and a slightly different pitch for the right channel pair, just to thoroughly optimize this situation.

The whole exercise can be made simple by using ethernet cable. If you get 'riser' CAT5 or CAT5e cable, it will consist of four twisted, solid conductor pairs that are insulated with PTFE, a great dielectric, wonderful sounding, and really easy to solder to, since it does not melt or shrink easily (which is why it's 'riser' cable - PTFE is fire resistant). Carefully slit open the jacket and you'll find four wonderful pairs inside that can be used for your tone arm wiring quite easily without any alteration. Someone else has already sweat the 'uniformity of pitch' and the 'slightly different twist pitch' details, so pick two pairs out of the cable and use them… done!
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Old 21st November 2014, 05:07 PM   #3
dtut is offline dtut  United States
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Straight Tracker,

It's good to hear you're making progress on your arm. Does this mean there'll be photos soon?

Monte McGuire's explanation of the benefits of twisting wires fits with my experience, but I've found that solid core wire is too stiff to work well in tonearms. If you're going to re-purpose wire, I suggest mouse wire. If you get a nice floppy length of it, it's light, stranded, twists easily, and doesn't hamper most arms. Check your local thrift store.

After twisting the wire pairs, one CW and one CCW with about six twists/inch, I just thread them through the arm randomly. I've done this in several arms with no hum problems. You may find you need a fifth ground wire.
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Old 21st November 2014, 06:34 PM   #4
kevinkr is offline kevinkr  United States
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Using metal arms I've never bothered to twist the wires (neither did SME on the arms I've rewired) and I've never had hum issues either.

Note if it is a wood or non-metallic arm twisting will help particularly if you are using a phono stage with a balanced input. Shielding is important in such a scenario too. Ground metal arm tubes with a separate wire as suggested.
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Old 21st November 2014, 11:44 PM   #5
AVWERK is offline AVWERK  United States
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The next time I do a tonearm I will twist each channel and keep it separated all the way from the cartridge to exit.
Don,t know if it will make any difference, but Basis turntable maker AJ Conti's new arm is.
The last air bearing Arm I rewired, the litz bundle was all twisted together and a seperate ground wire along with it was added, single ended.
This area never gets any attention and glad you brought it up

Regards
David
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Old 22nd November 2014, 02:49 AM   #6
dtut is offline dtut  United States
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Kevin,

I've had the same experience with metal - and carbon fiber - tonearms, but I just go with my usual belt and suspenders routine.
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Old 22nd November 2014, 09:09 AM   #7
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Default Thanks to everyone who responded to my questions

I can't go wrong now, with all the excellent answers I got. I am using a carbon fiber tone arm tube even though Frank Schroeder suggested that I "loose" it. I like Doug's CW/CCW suggestion and I think I will use it. I have several different litz tone arm wires. One of the samples I have was given to me by Frank Schroeder several years ago and it is the most flexible.

Doug,

I have had several delays in recent weeks but I should have some pictures ready in a week.

Sincerely,

Ralf
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Old 22nd November 2014, 12:29 PM   #8
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How about not putting the wires inside a tube but externally ?
It also helps to have it straight and not bending 90 ...
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Old 22nd November 2014, 04:11 PM   #9
Calvin is offline Calvin  Germany
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Hi,

I use silk spun HF Litz wires (5-7x 0.05) and twist two resp. three strands together.
The twisted wires are even softer than the single strands.
Inside the arm tube I use drinking straws to keep the channels clearly separated.
Also I use those small foam hearing protections for damping purposes.
One or two of these foam things introduce quite alot damping for carbon and metallic tubes, and they additionally fixate the straws.

jauu
Calvin
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Old Yesterday, 09:44 AM   #10
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Default Hi picowallspeaker

Quote:
Originally Posted by picowallspeaker View Post
How about not putting the wires inside a tube but externally ?
What would be the benefit?
And how would one attach the wires to the tonearm tube?

Sincerely,

Ralf
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