hi guys.
i was wondering how critical it is to twist the cables in class d amps from
power supply to amp and what`s the best way to do it since they 3 cables
and not 2.
thanks in advance..
i was wondering how critical it is to twist the cables in class d amps from
power supply to amp and what`s the best way to do it since they 3 cables
and not 2.
thanks in advance..
What are the cables carrying?
The twisting is an attempt to reduce loop area and to average out the magnetic field.
The twisting is an attempt to reduce loop area and to average out the magnetic field.
Get a sizable length of cable and tie one end of the bundle in a knot.
Slip the knot end over something strong.
Chuck the other end into a portable drill.
SPIN BABY SPIN!!!
Just be careful to pull tightly when the spinning is going on (This will keep your twists tight).
Be Careful when you loosen the chuck on the drill, keep control of the wire bundle with your second hand and control the spinout.
If you just let it go you run the risk of your nice twisted wire turning into a bundle of crap.
Slip the knot end over something strong.
Chuck the other end into a portable drill.
SPIN BABY SPIN!!!
Just be careful to pull tightly when the spinning is going on (This will keep your twists tight).
Be Careful when you loosen the chuck on the drill, keep control of the wire bundle with your second hand and control the spinout.
If you just let it go you run the risk of your nice twisted wire turning into a bundle of crap.
No !
The individual wires/cables must be contra-rotated to allow the twisting of the set.
Or do it by hand. You can feel the rotation necessary to allow the twisting to happen.
The individual wires/cables must be contra-rotated to allow the twisting of the set.
Or do it by hand. You can feel the rotation necessary to allow the twisting to happen.
The drill method is fine - manufacturers of twisted pair cable for ethernet cables, etc. effectively do it that way. It does impart a twist on the individual conductors, but unless you're doing a ridiculously high twist density, the conductors can handle it.
For the short runs you're talking about, just do it by hand. Cut the three conductors to length (give yourself extra length, as twisting will shorten the cable), zip tie one end together. Sit in a chair, one wire between your legs and one wire on each side of you, and start twisting the zip tied end, guiding everything together with your other hand. The three wires on the floor will spin a bit when you do this, make sure that they don't get tangled up in each other.
For the short runs you're talking about, just do it by hand. Cut the three conductors to length (give yourself extra length, as twisting will shorten the cable), zip tie one end together. Sit in a chair, one wire between your legs and one wire on each side of you, and start twisting the zip tied end, guiding everything together with your other hand. The three wires on the floor will spin a bit when you do this, make sure that they don't get tangled up in each other.
the cables are dc + - and ground.
my question was because of the three cables.
should i twist + with - and then on top of the twisted pear
the ground?
my question was because of the three cables.
should i twist + with - and then on top of the twisted pear
the ground?
now i saw that.
if i follow your advise i could use the ground for mid and twist on it the other two?
Just twist the three together - form the three wires into a "triangle" of sorts and twist them that way. Don't try to create an inner conductor or anything.
Where are the currents flowing in the +ve and -ve and ground?
An amplifier that has exactly equal +ve rail current and -ve rail current returns exactly zero current back up the ground wire. (please call it PSU Zero Volts to avoid confusing all those that think all grounds are the same).
If the amplifier is outputting some noise, that noise returns through the speaker return and that noise current passes back through the PSU Zero Volts to the PSU. Now when you measure the currents in the +ve and -ve supplies you will find they are very slightly different. So little you can ignore the noise current if the SNR is >100dB.
Now jump to an extreme case of a ClassAB amplifier pushing full power into the speaker load.
The +ve rail current returns via the speaker return to audio Ground and from there the speaker current returns via PSU Zero Volts to the PSU. Half a wave cycle later the speaker is moving the other way and it is drawing current out of the Speaker Return and sending it back to the -ve supply rail.
This weird operation of two different wires carrying the speaker current back and forth to the PSU is fundamental to ClassAB operation. It also, but to a more limited extent, applies to ClassA push pull amplifiers.
The three wires +ve, -ve & Zero Volts must be twisted as a triplet to allow the to and fro currents to cancel their fields between the alternating different pairs.
An amplifier that has exactly equal +ve rail current and -ve rail current returns exactly zero current back up the ground wire. (please call it PSU Zero Volts to avoid confusing all those that think all grounds are the same).
If the amplifier is outputting some noise, that noise returns through the speaker return and that noise current passes back through the PSU Zero Volts to the PSU. Now when you measure the currents in the +ve and -ve supplies you will find they are very slightly different. So little you can ignore the noise current if the SNR is >100dB.
Now jump to an extreme case of a ClassAB amplifier pushing full power into the speaker load.
The +ve rail current returns via the speaker return to audio Ground and from there the speaker current returns via PSU Zero Volts to the PSU. Half a wave cycle later the speaker is moving the other way and it is drawing current out of the Speaker Return and sending it back to the -ve supply rail.
This weird operation of two different wires carrying the speaker current back and forth to the PSU is fundamental to ClassAB operation. It also, but to a more limited extent, applies to ClassA push pull amplifiers.
The three wires +ve, -ve & Zero Volts must be twisted as a triplet to allow the to and fro currents to cancel their fields between the alternating different pairs.
If you twist by your described method then you have strained both the insulator sleeves and the conductor cores. The strains will be much higher than if the wires were twisted using the contra-rotating method.
Yes, absolutely true. A drill is a terrible way to do it.
Bulk wire twisting is done with jigs that allow the wire to rotate axially.
If one is twisting stainless lock wire using that little hand tool, then one is deliberately work hardening the wire to help it resist untwisting. That would be the intended purpose of the twisted lock wire.
That is not what one does to electric cables/cords.
That is not what one does to electric cables/cords.
so by contra rotating you mean twisting the to clock wise and the third counter clock wise?
If you are twisting the whole set/group of wires in a clockwise direction, then each individual wire of the group gets twisted anticlockwise.
Have a look for a U tube video of a wire cable winding/twisting machine. And see the complication they go to, to avoid excessive strain on the individual wires during the cable forming operation.
Have a look for a U tube video of a wire cable winding/twisting machine. And see the complication they go to, to avoid excessive strain on the individual wires during the cable forming operation.
I built star quads that ended up 3m long after twisting.
They started out quite a bit longer than 12'
I hung the 4 wire group on a door handle. It was not difficult nor was it particularly time consuming.
They started out quite a bit longer than 12'
I hung the 4 wire group on a door handle. It was not difficult nor was it particularly time consuming.
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