Expert: Dave Hathaway - 5/8/2005

Question
Thank you very much for the explanation & reference to the informative site.  Sir, could you give the details of AES/EBU format of digital audio?-------------------------
Followup To
Question -
Why in balanced audio, connections are termed as signal+, signal- and ground?
How to change a balanced audio in to an unbalanced audio and vice versa?
Answer -
Hello VP,

There are converters that will change a balanced audio line to unbalanced and vise-versa. These adapt an XLR balanced audio connector into a single ended RCA connector.

I am going to refer you go a very good site that has a complete discussion of this subject. I try not to re-invent the wheel when someone has already done a very good job of it.

Go to:

http://www.balanced.com/faq/balanced.html

and review this subject. If you still have specific questions, then just come back in with a follow up.

For your information--most of the consumer grade audio electronics we have available today use the unbalanced audio inputs with RCA pin connectors. The high end special (high priced) stuff has the three pin balanced XLR connectors commonly used with microphones in commercial public address systems. They have had these for years. While the unbalanced circuit seems to work very well for most of us, there are those who strive to achieve as near perfection as possible and thus the balanced audio circuit is now finding its way into the consumer electronics equipment.  I am not so sure this is not over kill, but one never knows?

Hope this gives you food for thought.

Dave

Answer
Hi again VP,

Balanced audio uses three wires to carry a single channel of audio. One is a ground wire and the other two carry an identical audio signal. One of these two audio wires in called the hot wire (number 1 or +) and the other is called the cold wire (number 2 or -).  This is just a way to designating which wire is which. The cold wire is running a signal that is in opposite phase to that of the hot wire. Normally, these signals would cancel out when they were combined at the receiving end of the cable. However, before this happens the cold wire is converted to the same phase as the hot wire and the signals actually combine to produce a larger audio signal.

So, why do all this stuff?  What happens is that any noise that gets onto the hot and cold wires is in-phase when it reaches the receiving end of the cable. When the phase reversal is done, the noise signals are now exactly out of phase and this signal is cancelled out--thus removing any noise picked up in the wire!! Neat huh?  Not super complicated and it uses very simple signal cancellation to do it.

A change from balanced to unbalance or vise-versa is accomplished by using special XLR connectors. How these are wired up is shown at this site:

http://www.mediacollege.com/audio/balanced

I recommend that you take a look and see how easy it is.
You just get the right connector to do what you want and solder up the balanced cable.

Let me know if you do this and how it worked.

See ya.

Dave