## balancing

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• hey there, maybe this is dumb question... if I record a balanced signal into two mono inputs, I m recording two 180-out-of-phase signals... and when
Message 1 of 5 , Oct 18, 2005
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hey there,
maybe this is dumb question...
if I record a "balanced" signal into two mono inputs, I'm recording two
180-out-of-phase signals... and when listening to them (over monitors) the
almost completely cancel eachother out (as they should)

so if I invert one side, am I basically balancing the signal? would it be
the same as properly recording a balanced signal?

Or is there more math involved that I'm unaware of..?

-pietro

http://geocities.com/pietrosammarco
http://geocities.com/chubbosound
http://geocities.com/openepo
http://theyshoothorses.org
• The idea of balancing is to create an out-of-phase version of the original signal and send both down the cable. Noise is picked up euqally and at the same
Message 2 of 5 , Oct 19, 2005
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The idea of balancing is to create an out-of-phase version of the
original signal and send both down the cable. Noise is picked up
euqally and at the same polarity in both wires. So in one wire you
have S+N and in the other you have -S+N. At the receiving end, the
two signals are subtracted, (S+N) - (-S+N) = S-(-S) + (N-N) = 2S +
0. The signal is restored and the noise cancels.

Technically then, to "balance" the signals at your monitors, you
would have to do this subtraction. Inverting one channel
accomplishes this by adding (acoustically) one channel and the
negative (inversion) of the other.

--- In micbuilders@yahoogroups.com, "Pietro M.P. Sammarco"
<pietro79@h...> wrote:
>
> hey there,
> maybe this is dumb question...
> if I record a "balanced" signal into two mono inputs, I'm
recording two
> 180-out-of-phase signals... and when listening to them (over
monitors) the
> almost completely cancel eachother out (as they should)
>
> so if I invert one side, am I basically balancing the signal?
would it be
> the same as properly recording a balanced signal?
>
> Or is there more math involved that I'm unaware of..?
>
> -pietro
>
>
> http://geocities.com/pietrosammarco
> http://geocities.com/chubbosound
> http://geocities.com/openepo
> http://theyshoothorses.org
>
• ... Actually, the signal does not have to equal and opposite in a balanced connection. Only the impedance that the reciever s differential inputs see needs to
Message 3 of 5 , Oct 19, 2005
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KenBobBrewsBeer wrote:

> The idea of balancing is to create an out-of-phase version of the
> original signal and send both down the cable. Noise is picked up
> euqally and at the same polarity in both wires. So in one wire you
> have S+N and in the other you have -S+N. At the receiving end, the
> two signals are subtracted, (S+N) - (-S+N) = S-(-S) + (N-N) = 2S +
> 0. The signal is restored and the noise cancels.

Actually, the signal does not have to equal and opposite in a
balanced connection. Only the impedance that the reciever's
differential inputs see needs to be the same, so that the
induced noise in the conductors is the same, and N - N = 0.
S2 and S3 absolute magnitude doesn't matter as long as
S2 - S3 = S, so S2 - 0 = S2 = S works.

> Technically then, to "balance" the signals at your monitors, you
> would have to do this subtraction. Inverting one channel
> accomplishes this by adding (acoustically) one channel and the
> negative (inversion) of the other.

AKA a difference amplifier. But the input impedance needs to be
the same so that the induced noise currents are the same.
The closer the match, the more perfectly cancelled the noise.

In a talk at an AES meeting given by Bill Whitlock of Jensen
Transformers, he mentioned that all the mic cables he was measuring
had slightly different capacitanec between each conductor
and the shield. When he asked the Belden engineers why that was
so, they said that the dyes to make the insulation different
colors always gave the insulation different dialectric properties.

-- Mike
• so then the answers to my questions if I invert one side, am I basically balancing the signal? would it be the same as properly recording a balanced signal?
Message 4 of 5 , Oct 20, 2005
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so then the answers to my questions "if I invert one side, am I basically
balancing the signal?
would it be the same as properly recording a balanced signal?" are "yes"?

>From: "KenBobBrewsBeer" <kenbob@...>
>To: micbuilders@yahoogroups.com
>Subject: [micbuilders] Re: balancing
>Date: Wed, 19 Oct 2005 12:38:39 -0000
>
>The idea of balancing is to create an out-of-phase version of the
>original signal and send both down the cable. Noise is picked up
>euqally and at the same polarity in both wires. So in one wire you
>have S+N and in the other you have -S+N. At the receiving end, the
>two signals are subtracted, (S+N) - (-S+N) = S-(-S) + (N-N) = 2S +
>0. The signal is restored and the noise cancels.
>
>Technically then, to "balance" the signals at your monitors, you
>would have to do this subtraction. Inverting one channel
>accomplishes this by adding (acoustically) one channel and the
>negative (inversion) of the other.
>
>
>--- In micbuilders@yahoogroups.com, "Pietro M.P. Sammarco"
><pietro79@h...> wrote:
> >
> > hey there,
> > maybe this is dumb question...
> > if I record a "balanced" signal into two mono inputs, I'm
>recording two
> > 180-out-of-phase signals... and when listening to them (over
>monitors) the
> > almost completely cancel eachother out (as they should)
> >
> > so if I invert one side, am I basically balancing the signal?
>would it be
> > the same as properly recording a balanced signal?
> >
> > Or is there more math involved that I'm unaware of..?
> >
> > -pietro
> >
> >
> > http://geocities.com/pietrosammarco
> > http://geocities.com/chubbosound
> > http://geocities.com/openepo
> > http://theyshoothorses.org
> >
>
>
>
>
• Yes, it should work as balanced. You can confirm it by taking your cable and opening the hood of your car and putting the mic cable over the top of the engine.
Message 5 of 5 , Oct 29, 2005
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Yes, it should work as balanced. You can confirm it by taking your
cable and opening the hood of your car and putting the mic cable over
the top of the engine. Then you can compare one mono input to the
pair under a high cable inserted noise environ.

Rich Peet

--- In micbuilders@yahoogroups.com, "Pietro M.P. Sammarco"
<pietro79@h...> wrote:
>
> hey there,
> maybe this is dumb question...
> if I record a "balanced" signal into two mono inputs, I'm recording two
> 180-out-of-phase signals... and when listening to them (over
monitors) the
> almost completely cancel eachother out (as they should)
>
> so if I invert one side, am I basically balancing the signal? would
it be
> the same as properly recording a balanced signal?
>
> Or is there more math involved that I'm unaware of..?
>
> -pietro
>
>
> http://geocities.com/pietrosammarco
> http://geocities.com/chubbosound
> http://geocities.com/openepo
> http://theyshoothorses.org
>
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