Question:

How can I prevent my microphone from picking up radio signals when it is partially plugged into an amp/dac? >
> I have a Mod Mic Uni microphone and hd58x headphones, both connected to a Schiit Fulla 3 amp/dac. When I unplug and replug the microphone jack, I hear a brief voice from a church radio station. When I insert the jack halfway, the radio station plays continuously through my headphones. This also affects the microphone volume and quality. What is the source of this interference and how can I eliminate it?

Answer:

How to Stop Your Microphone from Picking Up Radio Signals

Have you ever experienced hearing a radio station through your headphones when you plug in your microphone? This can be annoying and frustrating, especially if you are trying to record or stream audio. In this article, we will explain why this happens and how you can prevent it.

Radio interference is caused by unwanted radio frequency (RF) signals that invade your audio system. These signals can come from various sources, such as AM or FM radio stations, cell phones, walkie-talkies, or other wireless devices. They can interfere with your microphone, headphones, cables, or mixer, depending on how they are connected and shielded.

One common scenario is when your microphone cable acts as an antenna and picks up radio signals. This can happen if the cable is damaged, poorly shielded, or partially plugged into an amp/dac. The radio signals can then travel through the cable and reach your headphones, causing you to hear them.

Another possible scenario is when your amp/dac has poor common mode rejection. This means that it cannot filter out the radio signals that are present on both the positive and negative wires of the microphone cable. The amp/dac then amplifies the radio signals along with the microphone signal, making them audible through your headphones.

How to Prevent Radio Interference?

There are several ways to prevent or reduce radio interference in your audio system. Here are some tips and solutions that you can try:

• Use a good quality microphone cable. A good cable should have a thick and braided shield that covers the inner wires. This shield acts as a barrier that blocks the radio signals from entering the cable. You should also check the cable for any cuts, cracks, or loose connections that could expose the inner wires. If the cable is damaged, replace it with a new one.
• Plug the microphone cable fully into the amp/dac. A partially plugged cable can create a gap that allows the radio signals to enter the cable. Make sure that the cable is firmly and securely inserted into the amp/dac. You should hear a click when the cable is fully plugged in. If the cable is loose or wobbly, try a different port or adapter.
• Use a low pass filter or a transformer. A low pass filter is a device that blocks high frequency signals, such as radio signals, from passing through. A transformer is a device that isolates the microphone signal from the amp/dac signal, preventing them from mixing. You can place either of these devices between the microphone cable and the amp/dac to eliminate the radio interference. You can buy these devices online or from an electronics store. Some examples are the Shure A15RF RF Filter or the Markertek 1:1 Transformer.
• Change the location or orientation of your audio system. Sometimes, the radio interference can be affected by the proximity or direction of your audio system to the radio source. You can try moving your microphone, headphones, cables, or amp/dac away from the radio source, such as a window, a wall, or a power outlet. You can also try rotating or tilting your audio system to find a position that minimizes the radio interference.
• Use a different frequency or channel for your audio system. If you are using a wireless microphone or a wireless amp/dac, you can try changing the frequency or channel that they operate on. This can help you avoid the radio signals that are on the same or nearby frequency or channel. You can consult the user manual of your audio system to find out how to change the frequency or channel settings.

Conclusion

Radio

interference can be a nuisance for anyone who uses a microphone and headphones. It can ruin your audio quality and your listening experience. However, by following the tips and solutions in this article, you can prevent or reduce the radio interference in your audio system. We hope that this article has helped you solve your problem and enjoy your audio without any unwanted noise.