PA inbalance

[Humey]

During our last show our mixing desk started to show an inbalance of output. The left side was showing a strong signal where as the right showed a signifacantly weaker signal. I went out on the balcony to listen more closely to each side of the PA and there was a slight difference in volume. Now, would that be a problem with the desk, amp or speakers. I have a spair power amp to try. My first thought was just to replace the amp then if no difference replace the speakon cables etc etc.

 

Any ideas?

[Shez]

The left side was showing a strong signal where as the right showed a signifacantly weaker signal.

What do mean by showing? Were the meters on the desk showing that imbalance? Or were you just hearing it?

[Doug Siddons]

My guess would be he was looking at the output meters and they weren't equal and so the first thing to look at is the channel pans on the desk.

 

With regards to problem solving this, think about what is happening then try to work out where this is most likely to occur.If its not too rude, seeing as the desk is appearing to send out an unequal sgnal left and right why would you start to problem solve this by changing the power amp?

[MarkPAman]

What is the desk, what is going into it, out of it & what, if anything, is plugged into any insert points.

 

Start with a single (mono) channel, & check that with the pan in the middle you get the same signal level to both outputs. If not, check the routing - if you're using groups, are these set up correctly? Take out anything that is inserted over groups or the main outputs, like graphics or compressors. If there's still a difference then there may be a problem with the desk.

 

If you can do this & let us know the results we can probably narrow it down a bit more.

[dbuckley]

Once you've checked the desk for obvious things and drawn a blank, the next thing to do is swap the L&R outs on the desk over. If the fault stays on the side that was faulty, then the problem is downstream of the desk, so look to crossovers, amps speakers etc. If the fault swaps sides, its the desk, ouboard, or source.

[TimmyP1955]

Pull the bottom off of the mixer, unplug and replug every ribbon cable three or four times, and put the bottom back on.

 

(Had you told us what kind of desk, we might have more ideas.)

[Humey]

Desk is an Spirit FX16. Everything is panned straight down the middle. Only insert is a behringer graphic eq. If it is the mixing desk at fault, is that repairable? If not, I will need to buy a new desk. Can you suggest a good replacement for around £400?

[cedd]

Woah woah woah,

before we start talking about replacement, unplug that graphic and see what happens. Sounds like very little testing has happened yet, so I wouldn't go writing off the desk just yet.

 

In order;

un-patch the graphic - what happens?

 

Swap the left and right outputs over on the desk - does the fault move to the other speaker?

 

Do your testing with a mono input into a mono channel, panned central. Then your meters should be identical as should your output levels.

 

 

Following that, come back to us with your results.

[AV Doug]

Desk is an Spirit FX16. Everything is panned straight down the middle. Only insert is a behringer graphic eq. If it is the mixing desk at fault, is that repairable? If not, I will need to buy a new desk. Can you suggest a good replacement for around £400?

 

I had a similar issue with an FX16 we have and as someone else suggested it was a problem inside with the ribbon cable, ours actually needed replaced. In the end it went back to Soundcraft to get sorted and it cost alot less than a replacement. Can't remember the exact price but it was well under the £100 mark.

[Dexter1210]

You say there is a "slight" imbalance in the pa, if the left meter is showing a big difference to the right on the desk then im sure there would be more than a slight imbalance in the sound from the PA. I think im right in saying that on your desk activating PFL or SOLO swaps the left side out meter to show the PFL for whatever channel is selected leaving the right level meter showing normal output. I would check through and make sure none of the PFL/Solo buttons are depressed. The slight imbalance you describe could be another issue.