I am going to build some RCA interconnects using Gepco 6180EZ microphone cable and have a question maybe someone can advise me on.
The Gepco cable has a twisted pair of 22 gauge wire surrounded by a braided shield.
In the DIY RCA IC tutorial at the Emotiva Lounge Forum, the author posted pics where he combines the black wire with the braided shield and then uses the red wire as the positive lead.
Just wondering why you wouldn't combine the red and black leads for positive and use the braided shield as ground ?
On some other DIY posts online when using quad mike cable the 4 wires are combined to make a pair and the shield is used as ground . Just trying to understand why not in this gentlemans method.
thanks
The Gepco cable has a twisted pair of 22 gauge wire surrounded by a braided shield.
In the DIY RCA IC tutorial at the Emotiva Lounge Forum, the author posted pics where he combines the black wire with the braided shield and then uses the red wire as the positive lead.
Just wondering why you wouldn't combine the red and black leads for positive and use the braided shield as ground ?
On some other DIY posts online when using quad mike cable the 4 wires are combined to make a pair and the shield is used as ground . Just trying to understand why not in this gentlemans method.
thanks
Because twisting cancels out the magnetic field.
You can do what you propose, but you might as well just buy ordinary coax then. Which to be honest would be totally fine.
You can do what you propose, but you might as well just buy ordinary coax then. Which to be honest would be totally fine.
First mic cable is a sub-set of balanced interconnect cable. It is optimized for robustness, flexibility and low handling noise.
RCA is an unbalanced interconnect. The most important factor is low end-to-end resistance of the Shield/Return. For short lengths a mic cable will work just fine but it's not as easy to assemble as a well chosen coax cable.
RCA is an unbalanced interconnect. The most important factor is low end-to-end resistance of the Shield/Return. For short lengths a mic cable will work just fine but it's not as easy to assemble as a well chosen coax cable.
"Just wondering why you wouldn't combine the red and black leads for positive and use the braided shield as ground ?"
that totally defeats the purpose.
For best noise rejection you use the 2 wires for + and - and only solder the shield at one end of the cable (ground of course) and use that end at the source.
Best information on cables is this link Sound System Interconnection
that totally defeats the purpose.
For best noise rejection you use the 2 wires for + and - and only solder the shield at one end of the cable (ground of course) and use that end at the source.
Best information on cables is this link Sound System Interconnection
For coax connectors (including RCA) use coax cable. For balanced connectors (e.g. XLR) use twisted pair. Every transition from one to the other introduces the potential for problems, so I continue to be baffled why so many people seem to want to use twisted pair for unbalanced connections - whether external interconnects or inside a chassis.
I suspect that part of the reason may be that people know that professional sound systems use twisted pair so they assume that twisted pair must somehow be 'better' than coax. The only reason the pros use twisted pair is because the pros use balanced connections for audio. You don't get some of the advantages of balanced lines by using twisted pair in an unbalanced connection; you just get the disadvantages of using the wrong cable.
I suspect that part of the reason may be that people know that professional sound systems use twisted pair so they assume that twisted pair must somehow be 'better' than coax. The only reason the pros use twisted pair is because the pros use balanced connections for audio. You don't get some of the advantages of balanced lines by using twisted pair in an unbalanced connection; you just get the disadvantages of using the wrong cable.
Soldering the shield at one end creates an antenna, not a shield, shield needs to be connected at both ends to shield especially for RF shielding.
Just use a co-ax cable and do the job correctly, as stated previously the biggest factor is getting a really low resistance shield as this is carrying the return current and it is often the resistance of this shield that causes low frequency ground loops.......
Thank you for your comments explaining coax and twisted pair etc. , the link on sound System Connections is good
"It is true that connecting both ends of the shield is theoretically the best way to interconnect equipment -- though this assumes the interconnected equipment is internally grounded properly. Since most equipment is not internally grounded properly, connecting both ends of the shield is not often practiced, since doing so usually creates noisy interconnections."
I'll trust the experts at Rane, thank you.
You need to read exactly what they said. Their main interest was stopping buzz/hum. They admit that their one-ended shield may make RFI worse, so they suggest adding a capacitor at the ungrounded end too.Jsixis said:
RF terminated, maybe you should read in detail what has been put up...
When shielding low level analogue you need to shield it from RF (digital can be more tolerant of noise but not low level analogue) this involves creating a faraday gage around the equipment with a low impedance at the frequencies of concern
Of course I would recommend Henry Ott (or Ralph Morrison) over Rane on this matter, maybe you should read his stuff, he is one of the most respected experts in this field, they are all saying the same thing anyway...
Of course if the equipment is properly grounded inside then why use sub-standard gear or is it DIY stuff?
When shielding low level analogue you need to shield it from RF (digital can be more tolerant of noise but not low level analogue) this involves creating a faraday gage around the equipment with a low impedance at the frequencies of concern
Of course I would recommend Henry Ott (or Ralph Morrison) over Rane on this matter, maybe you should read his stuff, he is one of the most respected experts in this field, they are all saying the same thing anyway...
Of course if the equipment is properly grounded inside then why use sub-standard gear or is it DIY stuff?
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Some of the Rane papers are very old (one is almost 30 years old).
But for the most part, I think that the newer papers covering this area are based on the works of:
Keith Armstrong
Jim Brown
Ralph Morrison
Neil Muncy
Henry Ott
Doug Self
Bill Whitlock
and Rane's :: Stephen R. Macatee
But for the most part, I think that the newer papers covering this area are based on the works of:
Keith Armstrong
Jim Brown
Ralph Morrison
Neil Muncy
Henry Ott
Doug Self
Bill Whitlock
and Rane's :: Stephen R. Macatee
Ralph Morrison and Henry Ott are the two main men on this subject, look at papers by all the others and they generally have references back to these two, it is basically an EMC problem (noise) and is applicable to all electronics...
Of course there is nothing new in a lot of this and some stuff even goes back to the late 1800s such as twisted pair cables for noise reduction a legacy from the original signal integrity guy Oliver Heaviside....
Of course there is nothing new in a lot of this and some stuff even goes back to the late 1800s such as twisted pair cables for noise reduction a legacy from the original signal integrity guy Oliver Heaviside....
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