I'm building a 4pin XLR cable for headphones and am unsure about the proper construction approaches.
1) Using a starquad cable. 4 conductors are used for L/R +/-, but what to do with shield? Floating on both sides or connect to ground lug on XLR side? Does it have any effect when its not connected on either end?
2) Taking 2 * twisted pairs and run in parallel. Put heatshrink somewhere in the middle to form a Y. No shield in this case
3) Sames as (2), but use a shielded single conductor (instead of twisted pair), such as Mogami 2330. In this case, each channel is shielded separately.
Any pros/cons with these approaches? Which would be preferred?
P.S. I don't want to take the approach that some others take, by removing the individual conductors from the starquad out of the shield, and forming a braid with them
Thanks!
1) Using a starquad cable. 4 conductors are used for L/R +/-, but what to do with shield? Floating on both sides or connect to ground lug on XLR side? Does it have any effect when its not connected on either end?
2) Taking 2 * twisted pairs and run in parallel. Put heatshrink somewhere in the middle to form a Y. No shield in this case
3) Sames as (2), but use a shielded single conductor (instead of twisted pair), such as Mogami 2330. In this case, each channel is shielded separately.
Any pros/cons with these approaches? Which would be preferred?
P.S. I don't want to take the approach that some others take, by removing the individual conductors from the starquad out of the shield, and forming a braid with them
Thanks!
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I'm building a 4pin XLR cable for headphones and am unsure about the proper construction approaches.
1) Using a starquad cable. 4 conductors are used for L/R +/-, but what to do with shield? Floating on both sides or connect to ground lug on XLR side? Does it have any effect when its not connected on either end?
2) Taking 2 * twisted pairs and run in parallel. Put heatshrink somewhere in the middle to form a Y. No shield in this case
3) Sames as (2), but use a shielded single conductor (instead of twisted pair), such as Mogami 2330. In this case, each channel is shielded separately.
Any pros/cons with these approaches? Which would be preferred?
P.S. I don't want to take the approach that some others take, by removing the individual conductors from the starquad out of the shield, and forming a braid with them
Thanks!
Loads of useful information here Balanced Cables
Connect the shield to the XLR ground lug at the amplifier end to provide protection against RFI. Leave the shield floating at the headphone end.1) Using a starquad cable. 4 conductors are used for L/R +/-, but what to do with shield? Floating on both sides or connect to ground lug on XLR side? Does it have any effect when its not connected on either end?
Loads of useful information here Balanced Cables
Thanks.. I've seen that previously.
What I found a bit odd with his suggestion is to use both whites for 1st channel and both blues for the 2nd channel.
Even though the inner construction is all 4 wires twisted together, I thought a White/Blue pair would be preferred for each channel?
I don't see why that would be a preference over using a White/White & Blue/Blue pair.I thought a White/Blue pair would be preferred for each channel?
I don't see why that would be a preference over using a White/White & Blue/Blue pair.
When building a single channel XLR cable (3-pin), Canare specifically instructs to use both whites for pin 2, and both blues for pin 3.
http://www.canare.com/UploadedDocuments/Cat11_p35.pdf
".. in order to maximize noise rejection".
So basically using two twisted pairs for a single channel, right?
And the conductors are chosen in a way that + is twisted with -.
In similar fashion, in the headphone construction, since each pair is for a different channel, I would expect us to use the 2 twisted conductors.
The standard for 4 pin connection is to use two white wires for one pair and two blue wires for the other.
Q. What’s special about star-quad cable? |
Q. What’s special about star-quad cable? |
The standard for 4 pin connection is to use two white wires for one pair and two blue wires for the other.
Q. What’s special about star-quad cable? |
This is slightly different.
2 whites are used for +
2 blues are used for -
Due to the white/blue pairs, the + is twisted with the - for the SINGLE channel.
When using for conductors in the headphone, we will have 2 channels, so not utilizing the star quad advantage.
I understand that, so why are we agonising over the correct way to use star quad cable in your application?When using for conductors in the headphone, we will have 2 channels, so not utilizing the star quad advantage.
The short length of a headphone cable makes it pretty immune to RFI pick up anyway, so any decent 4 core screened cable should suffice.
Do you have a problem with RFI? I tried extending my headphone lead and had problems, using two coaxial cables cured it
No issues with RFI yet.
So similar to option 3 in the original post? Which cable did you use?
Yes, twisted pair per channel is best. Star quad does not have a pair of twisted pairs; it has a twisted quad, so however you wire it you may get interchannel crosstalk. It is the wrong cable for the job.itsikhefez said:In terms of the star quad, even though we aren’t using it as intended, I assumed that it would be preferable (even if only in theory) to use a twisted pair per channel.
If what you are doing is driving a pair of headphones - typically 32 Ohms these days - I really don't think you need to fuss about this. As long as the cables are in close proximity and the total area bounded by the signal and return is small (which it will be) you will be radiating insignificant EM energy and neither will you be picking anything up. Keep in mind your source impedance will be low, the headphone impedance is low, so cross talk is a non-issue in this application.
Re crosstalk, from here Star quad cable - Wikipedia
Star-quad cable can be used for two circuits, such as four-wire telephony and other telecommunications applications, but it will not provide magnetic immunity in this application. In this configuration each pair uses two non-adjacent conductors. Because the conductors are always the same distance from each other, crosstalk is reduced relative to cables with two separate twisted pairs. Each conductor of one pair sees an equal capacitance to both wires in the other pair. This cancels the capacitive crosstalk between the two pairs. The geometry also cancels the magnetic interference between the two pairs.
Star-quad cable can be used for two circuits, such as four-wire telephony and other telecommunications applications, but it will not provide magnetic immunity in this application. In this configuration each pair uses two non-adjacent conductors. Because the conductors are always the same distance from each other, crosstalk is reduced relative to cables with two separate twisted pairs. Each conductor of one pair sees an equal capacitance to both wires in the other pair. This cancels the capacitive crosstalk between the two pairs. The geometry also cancels the magnetic interference between the two pairs.
True for capacitive crosstalk. Irrelevant for magnetic crosstalk.Bonsai said:Keep in mind your source impedance will be low, the headphone impedance is low, so cross talk is a non-issue in this application.
To get low magnetic crosstalk you have to use the conductors in the right way. Use them wrongly and you get significant crosstalk - worse than a pair of twisted pairs.
I think I got that wrong.DF96 said:it has a twisted quad, so however you wire it you may get interchannel crosstalk. It is the wrong cable for the job.
Yes, twisted pair per channel is best. Star quad does not have a pair of twisted pairs; it has a twisted quad, ...
Yes, I had the wrong assumption that these were 2 pairs and not 4 conductors twisted together
Re crosstalk, from here Star quad cable - Wikipedia
Star-quad cable can be used for two circuits, such as four-wire telephony and other telecommunications applications, but it will not provide magnetic immunity in this application. In this configuration each pair uses two non-adjacent conductors. Because the conductors are always the same distance from each other, crosstalk is reduced relative to cables with two separate twisted pairs. Each conductor of one pair sees an equal capacitance to both wires in the other pair. This cancels the capacitive crosstalk between the two pairs. The geometry also cancels the magnetic interference between the two pairs.
This clarifies things. This means that if using star quad for 2 channels, we should actually use 2 blues and 2 whites (for Canare cable, for example), since those are non-adjacent to each other. This, as opposed to my wrong statement earlier to use blue/white for each channel.
Before this post I went on an extremely frustrating search to find cable that has 2 individual twisted pairs that would be suitable for headphone use.
I ordered a few samples of:
West Penn Wire D25430
Canare MR202-2AT
Belden 827232
I will have to decide between one of these and the starquad since I dont want to build multiple cables
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