If you enjoy listening to music and drive a car, you are probably well aware of how important a decent sound system is. But what should you do if your class D amplifier starts to encounter interference from your FM radio? Try the following to eliminate the radio interference caused by the class D amp:
1. Place the amp as far away from the stereo as you can.
2. Verify the proper ground
3. Attach ferrite clips.
4. Cover an amplifier in copper foil.
5. Install an AB Class 1 amp in its stead.
Table of Contents
Why D Class Amps Interfere With Radio Frequencies?
Class-D amplifiers work differently than class AB amps, constantly switching the output transistors on and off. Although the switching reduces the heat generated by the transistors and improves efficiency, the switching frequency not only overlaps with the AM or FM frequencies but also creates a lot of electromagnetic interference (EMI).
The EMI produced by class D designs can interfere with nearby electronic devices, including radios. Class AB amplifiers do not produce as much EMI because the output transistors are not switching, and the overall amplification logic is different. Class AB amplifiers use a continuous flow of current. This design produces less EMI and is less likely to interfere with radios.
Do All D Class Amplifiers Have This Issue?
Different class D amplifiers emit different amounts of EMI. Although certain class D amplifiers are built with particular filters that decrease the amount of EMI produced, this depends on the kind of processor, thus some amps may be more problematic than others.
Speaker cables begin serving as an antenna for the modulation frequency if the amplifier has no output filter (300KHz-600KHz). All three factors—the amplifier, stereo, and antenna type—affect the level of interference.
A high-quality shielded cable is required to connect the stereo to the antenna and the stereo to the amplifier.