(A Troubleshooting Guide to Finding Where Your Audio Signal Has Stopped)
By Dawie Nolte · Nolte Productions
Every dead sound system has one thing in common — the signal stopped somewhere. Find where it stopped, and you’ve basically solved the problem.
Something in your sound system has just stopped working. The first instinct is often to start pulling cables, changing settings and pressing buttons until something happens. I get it. When people are looking at you and nothing is coming through the speakers, it feels like you need to do something — and fast.
But random changes usually make things worse. You might get it working again, but then you don’t know what actually fixed it. Or worse, you’ve created another problem while trying to find the first one.
The good news is that most “no sound” problems come down to the same thing: the signal has stopped somewhere along the way.
So instead of guessing, let’s find out where.
Follow the Signal
Every sound system is basically a chain. Audio starts at a source, travels through a few different points, and eventually comes out of a speaker:
Source → Cable → Mixer Input → Channel → Routing → Output → Amplifier or Powered Speaker → Speaker
If there is no sound, the signal has stopped somewhere in that chain.
Your job isn’t to fix everything at once. It’s simply to find the point where the signal stops.
You don’t need to be a sound engineer to do this. You just need to work through it one step at a time.
Before You Touch Anything
Before you start unplugging things, take a few seconds and look at what is actually happening.
Ask yourself:
- What exactly isn’t working — one mic, one speaker, or the whole room?
- Was it working earlier?
- What has changed since then?
- Can you see any signal on the mixer’s meters?
- Has there been a power cut or load-shedding? Check the breaker, UPS or inverter before assuming the equipment has failed.
The most useful question, though, is this:
Where was the last place I know the signal was working?
For example, if you can see signal from the microphone on the mixer but you can’t hear it through the speakers, don’t waste time troubleshooting the microphone. You already know the mic and mixer input are working.
Now you can concentrate on everything after that point.
That one bit of information can save you a lot of time.
Start at the Source
If one microphone or instrument isn’t working while everything else is fine, start there before you start changing things on the mixer.
For a microphone, check the obvious things first. Is it switched on? If it’s wireless, is the battery charged? Is it muted? Is the transmitter actually connected to the correct receiver?
For an instrument, is it switched on? Is the volume turned up? Does it need a battery? Is it plugged into the correct output?
If you’re using a DI box — a small box that converts an instrument’s signal into something a mixer can use properly — check whether it needs a battery or phantom power. Phantom power is the 48V power some mixers send through the cable to run certain microphones and DI boxes.
One of the quickest ways to narrow things down is to use something you know works.
If Mic A isn’t working, plug Mic B into the same cable and the same mixer input. If Mic B works, you’ve probably found the problem — Mic A.
If Mic B also doesn’t work, keep moving down the chain.
Don’t Forget the Cable
A faulty cable is one of the most common causes of no sound, and it’s also one of the easiest things to overlook.
The cable might look perfectly fine and still have an internal fault.
Check that both ends are properly plugged in and that the connectors aren’t loose or damaged. But the best test is simple: replace it with a cable you know works.
Don’t spend ten minutes trying to prove that a cable is good when you have a known-good cable sitting in the cupboard.
Look at the Mixer Meter
This is one of the most useful things you can do.
Speak into the microphone or play the instrument and watch the channel meter.
Signal showing? Good. The mixer is receiving the signal, so the problem is further down the chain.
Nothing showing? Then the problem is before or at the mixer. Go back and check the source, cable, input and gain (how much the mixer is boosting that signal).
That little meter can tell you a lot more than randomly changing settings ever will.
There’s Signal, But Still No Sound
So the meter is moving, but you still can’t hear anything.
Now work through the channel.
Is it muted? Is the fader up? Is the channel assigned to the main mix?
If you’re using a digital mixer, also check the routing. A channel can look completely normal and still be routed somewhere you weren’t expecting.
This is one of the things that catches people out on digital mixers. Everything looks right — but the signal is simply going somewhere else.
What’s Coming Out of the Mixer?
If the channel looks fine, look at the main output meters.
Is there signal there?
If not, the problem is still somewhere inside the mixer. Check the mutes, faders and routing again.
If there is signal on the main output, then the mixer has done its job.
Now follow that signal to whatever is connected to the output. Make sure the cable is connected to the output you think it is and that it is actually going to the PA system you’re trying to hear.
Check the Amplifier or Powered Speaker
If the mixer is definitely sending signal, the next place to look is the amplifier or powered speaker.
If you have a separate amplifier, check that it is switched on, that there isn’t a fault or protect light showing, that the input level hasn’t been turned down and that it is receiving signal on the correct input.
With a powered speaker, check that it is switched on, the input level is up, it isn’t muted and that you can see some indication that it is receiving signal.
If the amplifier or speaker is showing that it is receiving signal and you still have nothing coming out, you’re now getting very close to the actual speaker problem.
One Speaker Down?
If one speaker is working and the other one isn’t, don’t immediately assume the speaker has failed.
Try swapping the left and right cables at the source end.
If the problem moves to the other side, the fault is somewhere before the speaker — possibly the output, cable or amplifier channel.
If the same physical speaker remains silent, then you can start looking at the speaker, its cable or its settings.
It’s a simple test, but it can save you a lot of unnecessary swapping around.
What If It’s a Laptop or PC?
Computers add a couple of extra places where things can go wrong because you’re dealing with both the computer and the sound system.
Connected with a Cable
Start with the computer.
Is the volume turned up? Is the correct playback device selected? Has it accidentally switched to Bluetooth or HDMI?
One of the easiest tests is to plug headphones directly into the laptop.
If you hear nothing through the headphones, the problem is on the computer.
If you do hear the audio, move on to the cable and then the mixer channel as you normally would.
Connected by USB
USB adds another layer because the computer has to recognise the mixer or audio interface as its output device, and the mixer has to be set up to receive that audio.
Simply plugging in a USB cable doesn’t automatically mean the audio will arrive where you expect it to.
If nothing is coming through, check both sides: where the computer thinks it is sending the audio, and where the mixer is expecting to receive it.
A Couple of Related Problems
This blog is about finding silence, not dealing with noise.
If what you’re actually hearing is a hum, buzz or hiss, that’s a different problem — I go into the causes and fixes for that one separately, so there’s no point repeating it all here.
And if it’s specifically a wireless microphone that keeps cutting in and out, that one’s more about batteries, pairing and interference than anything covered here.
And if what’s bothering you is more of a tone or clarity issue than total silence, that’s an EQ question, not a signal-path one.
A Few Things I Keep Coming Back To
When you’re standing in front of a silent PA and everyone is looking at you, remember these few things:
✔ Find the last point where you know the signal was working.
✔ Change one thing at a time. If you swap the cable, microphone and mixer input at the same time and it suddenly works, you still don’t know what the problem was.
✔ Use something you know works. A spare microphone, cable or input can tell you a lot more than guessing.
✔ And don’t forget the simple things. A muted channel or an unplugged cable causes far more “emergencies” than actual equipment failure.
What I’d Do
Most sound faults aren’t nearly as complicated once you stop guessing and start following the signal.
Work through the chain, use the meters to tell you where the signal stops, and use something known-good whenever you can.
It might take a few minutes longer than randomly flipping switches, but at the end of it you’ll actually know what was wrong — and hopefully you haven’t created three new problems while trying to fix the first one.
That’s the whole idea.
A quiet room isn’t a mystery. It’s just a signal waiting for you to find where it stopped.
Need a Hand Sorting This Out?
If you’ve worked through this and you’re still stuck — or you’d rather get it right the first time — email us at info@nolteproductions.co.za and we’ll help you get to the bottom of it.
— Dawie Nolte