Building a very low noise cable

在 1999年5月24日星期一 UTC+8 下�3:00:00，<PaulMmn> 写�：
> Assuming the input and output are balanced, a properly wired cable
> with XLR connectors should pass a balanced signal with no added noise;
> no special construction required.
> Balanced audio cables are 'shielded twisted pair,' with the signal
> being sent down the 2 leads of the twisted pair. Being a balanced
> signal, you 'push' your signal down one lead; the return path is the
> other lead.
> Looking at just the 2 wires of the twisted pair:
>
> Microphone element: D====================8|8==> Amplifier
> cable xformer
> Assuming a transformer-based amplifier, the cable and the mike element
> and the transformer winding to which it is attached form a closed
> loop. The desired signal loops around and around this loop, driven by
> the microphone element.
> Any noise that hits the cable will 'add voltage' to both of the wires
> (theoretically, because the wires are physically close together and
> the noise signal isn't fussy where it goes). When this noise voltage
> arrives at the transformer it goes in opposite ends of the same coil
> of wire and is electrically cancelled; it never shows up at the
> amplifier! Don't ask me to do the math; I have it on Good Authority
> that this is How It Works.
> the ground or shield
> RCA connectors are unbalanced connections. They send the signal down
> a center conductor, and use the "shield" (the outer conductor either
> spiral wrapped or braided around the center conductor) as the return
> path. This connection has no resistance to outside electrical noise
> (compared to the balanced connection above). The only reason RCA
> connections work as well as they do is because the home environment is
> reasonably noise-free (electrically speaking).
>
> *Begin possible BS*
> This following discussion assumes we're talking about balanced
> connections (see above). The cables involved have 2 conductors to
> carry the signal, and a 3rd to use as either the shield or the ground.
> From my recollection of articles read years ago, the premise is that
> you designate one piece of equipment (ie your mixer) as The Center.
> You then try to protect the signals running to and from The Center
> from interference.
> One method is to 'extend the shield' (as the Trekkers say) to include
> as much of and as many of the interconnections as possible.
> The sound-capturing mechanism of a microphone, for example, generates
> a balanced signal at its XLR connector. If the microphone is designed
> properly the sound-capturing mechanism is electrically isolated from
> the shell; plugging in a cable with the shield connected at both ends
> will connect the shell of the microphone to the shield of the cable to
> the shield connection of The Center. This surrounds the entire
> connection from The Center up to and around the microphone element
> with Shield.
> Microphones are relatively simple, until you add things like phantom
> power. So I won't go there.
> Connections from The Center to other equipment with their own shields
> get more complicated: The Shield of The Center is connected to
> ground, and the shield of the other equipment is connected to ground,
> and ground = ground (through the power line), so connecting shield to
> shield could form a loop. Theoretically, there is zero voltage
> between grounds of different equipment and between ground and shield.
> Theoretically. There can be voltage differences. These result from
> resistance in the circuitry involved, and the whim of Electrical
> Genies.
> Ground connections are usually routed back to a common point to try
> and avoid this problem: all outlets lead back (eventually) a common
> ground point where the power enters the building. The frame of a
> steel building is also grounded at this same point.
> Sometimes a facility (ie radio station or recording studio) declares a
> "Ground Point" for all of its facilities (ie a whole floor of an
> office tower). Everything the station/studio owns uses that ground as
> a reference (which everyone tries to make the same as the building
> ground).
> The differences in voltage between ground and shield and different
> pieces of equipment can be enough to be recognized as a signal by your
> equipment (ie Hummmmmmmm.....). This leads to discussions about
> disconnecting the shield at one end of a connecting cable (ie at the
> end of a cable farthest away from The Center) in an effort to prevent
> ground loops.
> *End possible BS*
> --Paul E Musselman
>
> On Wed, 19 May 1999 14:10:10 GMT, (Peter Berg)
> wrote:
> >Anybody got a recommendation for building a very low noise audio cable
> >from the SB Live to an external mixer?
> >
> >My current cable seem to pick up some humming at high levels.
> >
> >Shoud I try balanced cables?
> >
> >Cheers,
> >Peter

Low Noise cable has relationship with its low noise layer,generally ,if the low noise layer is graphene,you can realized good Low noise performance,compared with seme-conductive PVC or semi-conductive TPE.

More information,you can visit this
https://www.conectmed.com/category/l...-coaxial-cable

Pair twisting is a common way to reduce "Same frequency noise",Cat5,Cat6 are using this method.

Best Regards
Allen
Allen|International sales Director
Shen zhen Yong Qiang Fu Industry Co., Ltd.
HuBei Yong Qiang fu Technology Co.，Ltd.
Conectmed Technologies Co.,Ltd.
Headquarter Add：No.2 Building,Xinwei Village,the second industrial zone,Dalang Street,Longhua District,Shenzhen,China
Zipcode:518109
Phone:+86-755-28076259

Url：https://www.conectmed.com ;

On 24/12/2020 9:34 pm, Allen Shieh wrote:
> 在 1999年5月24日星期一 UTC+8 下�3:00:00，<PaulMmn> 写�：
>> Assuming the input and output are balanced, a properly wired cable
>> with XLR connectors should pass a balanced signal with no added noise;
>> no special construction required.
>> Balanced audio cables are 'shielded twisted pair,' with the signal
>> being sent down the 2 leads of the twisted pair. Being a balanced
>> signal, you 'push' your signal down one lead; the return path is the
>> other lead.
>> Looking at just the 2 wires of the twisted pair:
>>
>> Microphone element: D====================8|8==> Amplifier
>> cable xformer
>> Assuming a transformer-based amplifier, the cable and the mike element
>> and the transformer winding to which it is attached form a closed
>> loop. The desired signal loops around and around this loop, driven by
>> the microphone element.
>> Any noise that hits the cable will 'add voltage' to both of the wires
>> (theoretically, because the wires are physically close together and
>> the noise signal isn't fussy where it goes). When this noise voltage
>> arrives at the transformer it goes in opposite ends of the same coil
>> of wire and is electrically cancelled; it never shows up at the
>> amplifier! Don't ask me to do the math; I have it on Good Authority
>> that this is How It Works.
>> the ground or shield
>> RCA connectors are unbalanced connections. They send the signal down
>> a center conductor, and use the "shield" (the outer conductor either
>> spiral wrapped or braided around the center conductor) as the return
>> path. This connection has no resistance to outside electrical noise
>> (compared to the balanced connection above). The only reason RCA
>> connections work as well as they do is because the home environment is
>> reasonably noise-free (electrically speaking).
>>
>> *Begin possible BS*
>> This following discussion assumes we're talking about balanced
>> connections (see above). The cables involved have 2 conductors to
>> carry the signal, and a 3rd to use as either the shield or the ground.
>> From my recollection of articles read years ago, the premise is that
>> you designate one piece of equipment (ie your mixer) as The Center.
>> You then try to protect the signals running to and from The Center
>> from interference.
>> One method is to 'extend the shield' (as the Trekkers say) to include
>> as much of and as many of the interconnections as possible.
>> The sound-capturing mechanism of a microphone, for example, generates
>> a balanced signal at its XLR connector. If the microphone is designed
>> properly the sound-capturing mechanism is electrically isolated from
>> the shell; plugging in a cable with the shield connected at both ends
>> will connect the shell of the microphone to the shield of the cable to
>> the shield connection of The Center. This surrounds the entire
>> connection from The Center up to and around the microphone element
>> with Shield.
>> Microphones are relatively simple, until you add things like phantom
>> power. So I won't go there.
>> Connections from The Center to other equipment with their own shields
>> get more complicated: The Shield of The Center is connected to
>> ground, and the shield of the other equipment is connected to ground,
>> and ground = ground (through the power line), so connecting shield to
>> shield could form a loop. Theoretically, there is zero voltage
>> between grounds of different equipment and between ground and shield.
>> Theoretically. There can be voltage differences. These result from
>> resistance in the circuitry involved, and the whim of Electrical
>> Genies.
>> Ground connections are usually routed back to a common point to try
>> and avoid this problem: all outlets lead back (eventually) a common
>> ground point where the power enters the building. The frame of a
>> steel building is also grounded at this same point.
>> Sometimes a facility (ie radio station or recording studio) declares a
>> "Ground Point" for all of its facilities (ie a whole floor of an
>> office tower). Everything the station/studio owns uses that ground as
>> a reference (which everyone tries to make the same as the building
>> ground).
>> The differences in voltage between ground and shield and different
>> pieces of equipment can be enough to be recognized as a signal by your
>> equipment (ie Hummmmmmmm.....). This leads to discussions about
>> disconnecting the shield at one end of a connecting cable (ie at the
>> end of a cable farthest away from The Center) in an effort to prevent
>> ground loops.
>> *End possible BS*
>> --Paul E Musselman
>>
>> On Wed, 19 May 1999 14:10:10 GMT, (Peter Berg)
>> wrote:
>>> Anybody got a recommendation for building a very low noise audio cable
>> >from the SB Live to an external mixer?
>>>
>>> My current cable seem to pick up some humming at high levels.
>>>
>>> Shoud I try balanced cables?
>>>
>>> Cheers,
>>> Peter
>
> Low Noise cable has relationship with its low noise layer,generally ,if the low noise layer is graphene,you can realized good Low noise performance,compared with seme-conductive PVC or semi-conductive TPE.
>
> More information,you can visit this
> https://www.conectmed.com/category/l...-coaxial-cable
>
> Pair twisting is a common way to reduce "Same frequency noise",Cat5,Cat6 are using this method.
>
> Best Regards
> Allen
> Allen|International sales Director
> Shen zhen Yong Qiang Fu Industry Co., Ltd.
> HuBei Yong Qiang fu Technology Co.，Ltd.
> Conectmed Technologies Co.,Ltd.
> Headquarter Add：No.2 Building,Xinwei Village,the second industrial zone,Dalang Street,Longhua District,Shenzhen,China
> Zipcode:518109
> Phone:+86-755-28076259
>
> Url：https://www.conectmed.com ;
>

Sorry, the previous poster died of old-age.

geoff