[Allen Shieh]

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 ;

[geoff]

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