Have you ever downloaded a sermon you missed, put on your headphones and pressed play, only to be greeted with a horrible buzzing sound competing with the preacher? Today I’m going to show you how to get rid of this buzzing so that you can deliver clean, clear audio to your listeners.
Now, we’re going to be looking only at the most common form of audio hum, or buzz — A/C Ground Loop hum. If you’re interested in the electrical causes of ground loop issues, you can read more here.
The first step in removing ground loop hum is to figure out where it’s coming from. The easiest way to figure out where the hum is coming from is to remove absolutely every piece of equipment possible from your audio setup, and then introduce each piece, one at a time, until you hear the hum.
There are other ways to do this, like using the SOLO feature of your soundboard to listen to each channel to see if the hum is on the input of a certain instrument or microphone, but this won’t help you if the hum is introduced after the board, which is common in a recording setup where you’re only hearing the hum on the recording and not in the live output.
Once you’ve found the source of the hum, say a guitar’s amp or a DVD player, it’s time to try to get rid of it. Often, you’ll find that the source of noise is a result of a ground loop from using an unbalanced audio input in your sound system. You can find more information about balanced versus unbalanced audio signals in the notes.
A great solution to dealing with a ground loop can be to use a direct box to convert your audio from an unbalance to a balanced signal. If you plug your audio source in and you’re still getting the hum, try flipping the ground-lift switch and see if that kills the hum.
Another extremely common place that you run into hums is when you’re bringing audio into a computer for your recording. This type of hum is particularly nefarious because you usually won’t hear it until you listen to the recording later. (On a side note, it’s always worth having a pair of headphones and checking the audio quality of your recording during the service so you can find issues like this before they ruin an entire recording).
Now, when dealing with bringing audio into a computer, you’re introducing an entirely new set of possible causes of buzz. One solution can be to use an opto-isolator to prevent an actual electrical bridge between your audio source and the computer.
Another trick is to use the same direct box here that you would use to bring an acoustic guitar into your system, but run it in reverse to your recording device. Again, try toggling the ground lift switch to see if that takes care of your problem.
If you’re using a laptop to record, try pulling the power cable and let the laptop run on batteries. If the hum stops, you know that it’s an issue with your power supply.
If the computer you record with is also being used for projection, try pulling the cable to the projector and see if the hum stops. This is pretty common, and also pretty difficult to deal with.
Unfortunately, if you determine that your recording computer is the cause of the buzz there are often no easy solutions. You can try to find various types of isolators; you can try to ensure that your equipment all shares a common ground, and you can ensure that everything is properly shielded, but sometimes the hum just isn’t going to go away.
If you’re dealing with hum, or if you’re just starting out with recording your sermon audio, we highly recommend you use a stand-alone audio recording device like this one or this one. This recorder takes a balanced signal input, right from an aux-out on your sound board, and records right to an SD Card. When the recording is finished you can copy the file over to your computer and edit it as necessary.
This recorder can run off a few AA batteries or with the supplied power adapter, and it even has a headphones plug for monitoring the recording while it’s happening.
Now, audio engineering is a complicated topic, and we’ve only barely touched on the issue of hum. Hopefully if you’re experiencing some hum one of the solutions we talked about today can help clean up your recordings.
If you have any other tips on dealing with audio hum, please drop your suggestions in the comments or in the forums. In future episodes we’ll dive deeper into audio engineering with more practical tips for improving the quality of your sermons, so subscribe to our channel today to get notified when we post those episodes. For Sermons.io, I’m Jeff McFadden. See you next time.
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