----------------------------------------------Jocko Homo said:
dCS972/954, which makes most CDs enjoyable if upsampled to 24/192. Very sensitive to cables even on the BNC 75R connections but very musical. Bought for an excellent price in Hong Kong. Should be even cheaper now if you dare go!
Twisted pair inductance/capacitance?
I know that with twisted pair cable we get some inductance in the cable. This is when the (+) and (-) are twisted together.
If we twist together 3 strands of wire and use it as a single (+) and twist together 3 more strands of wire and use it as a single (-), is there still inductance if the (+) & (-) conductors are not twisted together?
Any help would be appreciated.
Thanks
KevinLee
I know that with twisted pair cable we get some inductance in the cable. This is when the (+) and (-) are twisted together.
If we twist together 3 strands of wire and use it as a single (+) and twist together 3 more strands of wire and use it as a single (-), is there still inductance if the (+) & (-) conductors are not twisted together?
Any help would be appreciated.
Thanks
KevinLee
Hi Kevinlee,
Here is a good article. I haven't read it fully yet, but it deals with the subject well:
http://www.brandrex.com.au/bptute.htm
It says that the twist affects crosstalk. It does not suggest any inductance / impedance change.
You might like to have a look:
Cheers,
Here is a good article. I haven't read it fully yet, but it deals with the subject well:
http://www.brandrex.com.au/bptute.htm
It says that the twist affects crosstalk. It does not suggest any inductance / impedance change.
You might like to have a look:
Cheers,
I do not know what you mean by "78R and 100R" twisted pair.
Does the R mean impedance? As in 78 Ohm cable and 100 Ohm cable?
If you are talking about digital connections, them 75 ohm coax is by far the cable will be the closest. I know that Belden 9451 balanced audio sheilded twisted pair cable works out to be about 80 ohms, but Belden does not advertise it.
Belden is big in the world wire market. If you can find a Belden part number you like, then you should be able to cross reference it against what you can find locally in small quantities.
For Digital audio, the AES/EBU balanced cable spec is 110 ohm +/- 20%. No - really twenty percent. It is pretty forgiving. Most of the transmit and recieve electronics are of such a quality, that you can get away with much greater impedance sins.
That +/- 20% spec also explains why you do not need to go out and buy 100 ohm XLR connectors.
More than you might ever want to know (or more than you thought you could know) about wires and cables can be found at:
http://bwcecom.belden.com/college/college.htm
Aud_Mot
Does the R mean impedance? As in 78 Ohm cable and 100 Ohm cable?
If you are talking about digital connections, them 75 ohm coax is by far the cable will be the closest. I know that Belden 9451 balanced audio sheilded twisted pair cable works out to be about 80 ohms, but Belden does not advertise it.
Belden is big in the world wire market. If you can find a Belden part number you like, then you should be able to cross reference it against what you can find locally in small quantities.
For Digital audio, the AES/EBU balanced cable spec is 110 ohm +/- 20%. No - really twenty percent. It is pretty forgiving. Most of the transmit and recieve electronics are of such a quality, that you can get away with much greater impedance sins.
That +/- 20% spec also explains why you do not need to go out and buy 100 ohm XLR connectors.
More than you might ever want to know (or more than you thought you could know) about wires and cables can be found at:
http://bwcecom.belden.com/college/college.htm
Aud_Mot
KevinLee said:Twisted pair inductance/capacitance?
I know that with twisted pair cable we get some inductance in the cable. This is when the (+) and (-) are twisted together.
If we twist together 3 strands of wire and use it as a single (+) and twist together 3 more strands of wire and use it as a single (-), is there still inductance if the (+) & (-) conductors are not twisted together?
Any help would be appreciated.
Thanks
KevinLee
Hi
A straight wire shows some inductance, about 1 uH each meter.
Paralleling both curents (origin and return) electromagnetically couples the wires, reducing the inducatance. A normal mains cable has about 600 nH per meter
Twisting even couples them tighter, but also increases the capacitance, hence, the impedance lowers.
Coax has real high mutual coupling, as the screen is realy closed, no EM field will trade outside the cable. The impedance achieved is about 50 ohm, or sometimes lower
The same can be achieved on a double layer PCB (1.6 mm epoxy), where you have 3 mm width tracks running over a groundplane: Also about 50 ohm
Back to the twists: By playing with the number of twists, the diameter and the tightness, we can affect the impedance
I will keep you update
best regards
Twisted
RTFB it has the formulas. This is the reference text on transmiison lines. Most twisted pair is around 110 ohms. You have to know the wire geometry or do TDR ( highly recommended) I am curious what connects use plan to use since most connectors for 110 ohms are very bad impedance matches.
http://www.amazon.com/exec/obidos/t...f=sr_1_2/002-0939699-6058406?v=glance&s=books
RTFB it has the formulas. This is the reference text on transmiison lines. Most twisted pair is around 110 ohms. You have to know the wire geometry or do TDR ( highly recommended) I am curious what connects use plan to use since most connectors for 110 ohms are very bad impedance matches.
http://www.amazon.com/exec/obidos/t...f=sr_1_2/002-0939699-6058406?v=glance&s=books
It's amazing!
How many knocks can the production / broadcast industry AES / EBU standards get?
There, 90% of all digital audio interconnects are 110 ohm, and coupled through XLR's. Digital audio is regularly and reliably sent up to 250 metres down 110 ohm twisted pair cable, which according to some, is also rubbish.
Sometimes it's sent through a "Krone Frame". That's a series of IDC connector blocks that were designed for the telecoms industry, though then they generally don't go the full 250m. The system was designed with ruggedness in mind. Does it cause any problems? No. Are there problems? Yes, sometimes, but always to do with the equipment or it's reference, or an obviously bad connection.
Most of the audio that is used for our tests has been through all this. Is the audio rubbish? Well some is, but probably for other reasons
How many knocks can the production / broadcast industry AES / EBU standards get?
There, 90% of all digital audio interconnects are 110 ohm, and coupled through XLR's. Digital audio is regularly and reliably sent up to 250 metres down 110 ohm twisted pair cable, which according to some, is also rubbish.
Sometimes it's sent through a "Krone Frame". That's a series of IDC connector blocks that were designed for the telecoms industry, though then they generally don't go the full 250m. The system was designed with ruggedness in mind. Does it cause any problems? No. Are there problems? Yes, sometimes, but always to do with the equipment or it's reference, or an obviously bad connection.
Most of the audio that is used for our tests has been through all this. Is the audio rubbish? Well some is, but probably for other reasons
twist and shout
XLR were never designed for high frequency signal. Impedance matching can be harder to do than with coax. I designed digital cables and digital interfaces for high applications. The SECOND best high end AES EBU cable used two 55 ohm coax. Digital cable are directional since the geometry varies slightly along it's length. This is very audible on many coax and will show up in jitter measurements. With two different sex connector you can't turn the AES EBU around. The original AES spec was revised since it allowed for multiple receiver connections with the drawback of gross impedance mismatch as I recall. The high signal levels make the mechanical damping very important for a decent sounding cable design.
XLR were never designed for high frequency signal. Impedance matching can be harder to do than with coax. I designed digital cables and digital interfaces for high applications. The SECOND best high end AES EBU cable used two 55 ohm coax. Digital cable are directional since the geometry varies slightly along it's length. This is very audible on many coax and will show up in jitter measurements. With two different sex connector you can't turn the AES EBU around. The original AES spec was revised since it allowed for multiple receiver connections with the drawback of gross impedance mismatch as I recall. The high signal levels make the mechanical damping very important for a decent sounding cable design.
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