balanced/unbalanced

[Sidhu]

what are the real advantages of having balanced inputs/outputs ??? will not the unbalanced outputs of a mixer (UB502, TS) into the unbalanced inputs of a Monitor (Event TR6, RCA) sound as good, as say their XLR counterparts ?? also for other connections, especially over rather short distances ??

also why wud a small mixer like the UB series (Behringer), have balanced line inputs but unbalanced outputs ?????


thank

Sidhu

[ObsoleteAcc99]

[DELETED]

[Glooper]

balanced signals will remove most noise produced through EM interference. It does this by reversing the audio signal and sending down both the reversed audio signal as well as the original. If EM interference occurs on the wire then it will create a similar glitch on both the reversed and original signal. When recreating at the other end of the wire it will unreverse the reversed signal and add the two signals together, thus any interference in the signal that was created along the wire will be cancelled out. (Hmm... I hope that makes sense!... I'm note sure I've explained it very well!!)...

Generally mic leads will use balanced cables as the signal is at low volumes so any cable noise will be amplified by the mic pre-amp. Whereas, out signals are hotter so there is less of a need for a balanced out cable as the Signal to Noise ratio is less. Though better quality set-ups will allow for balanced cables throughout.

Ben

[Sidhu]

balanced signals will remove most noise produced through EM interference. It does this by reversing the audio signal and sending down both the reversed audio signal as well as the original. If EM interference occurs on the wire then it will create a similar glitch on both the reversed and original signal. When recreating at the other end of the wire it will unreverse the reversed signal and add the two signals together, thus any interference in the signal that was created along the wire will be cancelled out. (Hmm... I hope that makes sense!... I'm note sure I've explained it very well!!)...

Generally mic leads will use balanced cables as the signal is at low volumes so any cable noise will be amplified by the mic pre-amp. Whereas, out signals are hotter so there is less of a need for a balanced out cable as the Signal to Noise ratio is less. Though better quality set-ups will allow for balanced cables throughout.

Ben

well i thought hard...

and this is what i figured...

take the example of the XLR cable. Say for a microphone.

pin 1 sheild
pin 2 hot
pin 3 cold

pin 2 carries the correct signal.

pin 3 carries the reversed signal. (this reversal is done by the microphone itself.

pin 1 ground


the mixer then reverses what it sees on pin 3. Thus bringing the siganl in phase with what is on pin 2.

it then sums both the signals from pin 2 and 3. (in the process reversing the phase of the EMI and cancelling it)

This also leads to the doubling of amplitude which is why balanced signals are louder than unbalanced ones (but what bout input impedence ? )

Also what role is then played the sheild.. Is it's purpose to first try and block any interference ? and if there is any, then the phase reversal trick comes into play ?

please tell me if i am mistaken on any account.

thank you

sidhu

[Glooper]

well i thought hard...

and this is what i figured...

take the example of the XLR cable. Say for a microphone.

pin 1 sheild
pin 2 hot
pin 3 cold

pin 2 carries the correct signal.

pin 3 carries the reversed signal. (this reversal is done by the microphone itself.

pin 1 ground


the mixer then reverses what it sees on pin 3. Thus bringing the siganl in phase with what is on pin 2.

it then sums both the signals from pin 2 and 3. (in the process reversing the phase of the EMI and cancelling it)

That sounds about right.

This also leads to the doubling of amplitude which is why balanced signals are louder than unbalanced ones (but what bout input impedence ? )

I don't think the amplitude is doubled as the signal is originally split at the sending end. So the there is no net gain in volume.

Also what role is then played the sheild.. Is it's purpose to first try and block any interference ? and if there is any, then the phase reversal trick comes into play ?

Phase reversing could get rid of most noise. However it's not perfect as one wire can be more effected by EMI than another, or a glitch can occur on just one wire. So using both Shielding and XLR is going to reduce the EMI in two ways..

Though you do realise I don't really know this!! I'm just guessing from my basic understanding of electronics and having played with these connections.

Ben

[Sidhu]

I don't think the amplitude is doubled as the signal is originally split at the sending end. So the there is no net gain in volume.

i dont quite understand split ????

Though you do realise I don't really know this!! I'm just guessing from my basic understanding of electronics and having played with these connections.

u have done a very good job at putting it across to me.. so thank you for that.

if either one of us is wrong then please correct us..

thanks a ton.

[Glooper]

I don't think the amplitude is doubled as the signal is originally split at the sending end. So the there is no net gain in volume.

i dont quite understand split ????

Yes , you have 1 input signal... That signal is split so that the reversed signal can be created.

Ben

[Sidhu]

Yes , you have 1 input signal... That signal is split so that the reversed signal can be created.

meaning that when the signal is split (by the source) the strenght of the signal is devided into the two cores ??? and hence when they meet at the destination (and return to coherent phase) the summing of the two (which happens ?) does result in twice the amplitude, but is equall to the amplitude of the original signal ???

am i correct ?


I also do not now understand why is it that a balanced signal has a higer level than unbalanced signal ? and why does the mixer have an impedence of 20 kilo ohms for balanced inputs but 10 for unbalanced ???

thanks

[Glooper]

meaning that when the signal is split (by the source) the strenght of the signal is devided into the two cores ??? and hence when they meet at the destination (and return to coherent phase) the summing of the two (which happens ?) does result in twice the amplitude, but is equall to the amplitude of the original signal ???

am i correct ?

I think so... But can't be certain

I also do not now understand why is it that a balanced signal has a higer level than unbalanced signal ? and why does the mixer have an impedence of 20 kilo ohms for balanced inputs but 10 for unbalanced ???

thanks

Okay...I think you've reached the limit of my knowledge now!... I didn't realise they did have a higher level?... as to the impedence thing I have no idea. . My suggestion is to do a net search to find some more indepth information.

Ben

[DevonB]

The part you're missing is the 180 degrees out of phase, which won't increase amplitude.

What makes a balanced connection work, is some electronic trickery that makes the noise on the line phase cancel itself out of existence. (Remember our feature on Phase?) Here's how it happens. A balanced connection first runs through a differential amplifier which splits the hot signal into two and flips one half 180 degrees out of phase. This travels along the cable as plus and minus along with the ground on three separate conductors (on an XLR, pin 2 is hot, pin 3 is cold and pin 1 is ground). Along the way, the usual noise is encountered and picked up by the line. At the other end of the connection, the minus is flipped back into phase and you end up with a plus and a ground again, just as it was when you started. The difference is, that now the noise is out of phase with itself and cancels completely.

http://homerecording.about.com/library/ ... 082697.htm

Devon

[Sidhu]

I understand the 180 flip. But when the siganl reaches the destination it is phase reversed again. Which will bring it in phase with the correct signal. And two identical signals with coherent phase, when summed together will result in an increased amplitude. Right ?

also what is a differential amplifier ??


thanks for getting bak..

and i guess well take it together from here Glooper...

on the link.