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Old 26th June 2003, 03:48 PM   #1
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Default which wires to twist?

in my gaincone, which wired should i twist together? power (AC)? power (DC)? Signal? Output?
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Old 26th June 2003, 03:53 PM   #2
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I would twist the AC power lines into the transformer....DC power lines to the amp and signal lines same thing...key is make sure they dont run parrallel to each other....if they do cross them

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Old 26th June 2003, 05:35 PM   #3
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which shouldnt run parrellel? power and signal?
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Old 26th June 2003, 06:14 PM   #4
RobM is offline RobM  United States
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Twist the power rails together, but not together with ground.
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Old 27th June 2003, 05:48 AM   #5
Mad_K is offline Mad_K  Norway
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Quote:
Originally posted by RobM
Twist the power rails together, but not together with ground.

and why is that?
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Old 27th June 2003, 10:53 AM   #6
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When you twist two cables it should be twisted between signal and ground (or voltage and ground for PSU).
As Kimber does with their interconnects and speaker cables.
Read the datasheets, it's all there.
Manufacturers recommend twisting the cables.

I always twist.
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Old 27th June 2003, 12:17 PM   #7
Jennice is offline Jennice  Denmark
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Default Twisting the field away...

RobM,

I can't see why your approach should improve things ... but I'm eager to learn.

The way I see it, a conductor should be twisted with it's "mate", meaning that a signal and it's return path should be twisted.

For signal lines, it's a matter of shielding them to obtain immunity against radiated noise.

In the case of a power conductor, it's to minimise the emission of noise.

The most powerful noise source in terms of radiation is between your mains transformer and the bridge rectifier, and between the rectifiers and the power supply capacitors. They're charged at high currents over short time in bursts, and it's the current that creates this field we want to minimize. The way to do this would be to
1) lower the current, which isn't really an option...
2) have the conductor and it's return path run in a tight parallel.
The resulting field of two wires carrying a current in opposite directions is ideally zero. (Not in reality, but it's close)
The twisting is a practical way of keeping them together while the fources of nature (laws of magnetism) try to push them away from each other.

In terms of the high order harmonics, it's basically the same concept, except that we're talking about the voltage drops from one end to the other which creates an antenna. Again, the vecor sum of two opposite antennas is ideally zero.
In other words, it's a matter of keeping a conducted current and it's return path close.

If you have a design where the ground is truely not carrying any current, you can leave it out. Then again, you will then no longer have a useful amplifier.

Imagine the amp turned on, and no signal applied.
Your output will be at ground potential (roughly), and the supply current/bias runs from the positive supply through the amp and output stage (especially for class A designs) to the negative supply rail and back to the supply's negative part. Then, your ground is not participating.

When a positive signal is applied to a non-inverting class B amp, the current runs from the positive supply rail through part of the output stage, then to the speaker, and back to the speakers negative terminal. This terminal is a ground line. NOW the ground is "actively" participating as is conducts current

The concept is basicallt the same for class A amps, except the entire output stage is conducting at all times.

The SUM of currents is constant (zero), and now you'll need to include the ground in your twisting of supply conductors, to avoid creating electric and magnetic fields in your amp.

I'm not native to english, but I hope this all makes sense (somehow )

Jens
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Old 27th June 2003, 01:38 PM   #8
Mad_K is offline Mad_K  Norway
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VERY good explanation Jens
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Old 27th June 2003, 02:04 PM   #9
Jennice is offline Jennice  Denmark
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YEAHhhh!
Someone understood me *grin*
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Old 27th June 2003, 02:28 PM   #10
Nuuk is offline Nuuk  United Kingdom
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Jennice, that was a good explanation about twisting wires.

Would you mind if I copied it for use on Decibel Dungeon? I would of course give you full credit for it.

I want to gather enough material for another page of slightly more advanced hi-fi subjects and this is the sort of item that I am looking for.
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