AussieM8

Hi guys

I've been looking at a cheap PA system for the outdoor area and picked up a single speaker/amplifier which has twin XLR inputs (3 pins). The manual states that [Line 1 In] and [Line 2 In] can be used in "balanced" or "unbalanced" mode.

My questions are:
> What does "balanced" and "unbalanced" mean?
> Are the XLR inputs stereo or mono inputs?
> If mono, I assume I can use [Line 1 In] for left and [Line 2 In] for right?
> What type of adapter is suitable to this situation?

What I would like to do it connect my PC's stereo out signal so I can play MP3's through the speaker.

A search for an adapter on the net has only confused me, so I thought I would turn to my friends at austech

AussieM8

Here's a couple of connectors I found ... should they work?

therufus

The adapter cable should work. More information on the PA system would help.

Studio1

Ok, well you have come to the right place as pro-audio is my main field of work (in the radio broadcast industry).

Balanced inputs have three connections - ground, cold and hot.
Unbalanced inputs have two - ground and hot.

Without going into the theory of balanced lines, such an input expects to see two signals - one that is in phase, and one that is 180° out of phase.

If you look at the XLR connector you will see three pins - numbered 1, 2 and 3 respectively.

1 = ground
2 = hot
3 = cold

A balanced input also expects to see a particular level of audio.
If it is a line input, it expects to see around +4dBm of audio. A standard unbalanced output (RCA etc) provides around -10dBV - ie, a whole lot lower.

You can run a balanced input with an unbalanced signal. Simply connect pin 3 to pin 1 (cold to ground) and feed your audio in on 2 and 1 (2 being "hot" and 1 being ground).

So, your unbalanced device (mp3 player, CD player etc) will drive a balanced input in this fashion, but you may find it lacks level, for the reasons given above - and you may have to turn everything up a lot more to get the same sound levels out of the amp.

XLR connectors are MONO. Each connector carries one channel of audio. You will find that one XLR connector on your PA corresponds to one channel on the front panel - or one fader etc.

Yes, you can use line 1 for left and line 2 for right, assuming that the amp can mix both inputs at once. Is the output of the amp stereo?
Normally, PA amps have mono inputs and mono outputs.

If you use line 1 as left, and line 2 as right, and the amp has mono outputs, it will simply mix line 1 and 2 together, to give you mono out anyway.

If the amp has stereo outs, then you should see some "PAN" pots on the front - allowing you to steer the signal from each channel to either the left output, the right output, or somewhere in between.
If this is the case, turn the line 1 panpot hard left, the line 2 panpot hard right, and this will give you stereo on the outputs.

Any standard 3 pin XLR connector can be used to hook in. The ones you show there will be fine. As you can see they already have pins 1 and 3 connected together.

If you get stuck, come back for more advice