What should I do about interference caused by radio noise?

With the advancement of technology, it has become common to be surrounded by radio waves. This page introduces countermeasures against electromagnetic noise from AC/DC Power Adapters — Desktop & Wall-Mount.

Noise issues are a particularly headache-inducing challenge.

We offer the following proposals as countermeasures against electromagnetic noise interference.

About Noise Countermeasures for AC Adapters

We have received many from customers asking what can be done about interference caused by electromagnetic noise from AC adapters.

Although we refer to it collectively as noise, there are various classifications and requirements such as communication-related noise and audio-related noise. This time, we would like to present a real-world example of a unique type of audio noise known as "Beat Noise".

Beat Noise is a type of noise that appears as diagonal stripes on analog television signals during image reception. (This includes things like ripple noise and interfering sine waves.) In other words, when multiple devices such as large speakers and guitar amps are connected on a concert stage and there is no sound yet, a howling or ringing noise may be emitted from the speakers — this is Beat Noise.

These phenomena are caused by noise generated from the power source flowing through to the speakers, creating unpleasant sound. Typically, this occurs when the ground (GND) of an AC adapter and the GND of the signal connection form a loop connection. Addressing causes such as insufficient gain and carrier wave interference is often quite difficult.

Currently, UNIFIVE is developing custom solutions for our customers in the audio equipment industry and has adopted the following design improvements to resolve this issue.

① Separate the GND connection between the primary and secondary sides of the AC adapter

② Add ferrite beads to the internal ceramic capacitors of the AC adapter

Implementation is done as shown in the reference photo below.

③ Modify the internal transformer pin connections of the AC adapter

Change the connection from Pin 1 to Pin 2 for the lead wire (shown in black) on the transformer core side.

These improvements allow comparison of the measured waveform diagrams.

By implementing these countermeasures, if the waveform becomes closer to a sine wave with lower amplitude, low-frequency audio noise will be reduced.

The output specification of the adapter after implementing these measures is 13.0V/4A. These Products are used by customers for guitar amps and similar applications.

Our company, UNIFIVE, has extensive experience and a strong track record working with many audio equipment manufacturers. As a result, we have a wide range of experience developing AC adapters with custom noise countermeasures, including the design philosophy of IEC60065 audio safety standards, improvement techniques for audio noise by 6dB–12dB, long-life component selection, electrostatic discharge protection, support for high customization demands (such as gas corrosion resistance for metal pins and Beat Noise reduction), and more.

The audio equipment on the market is increasingly adapting to the digital era of devices. From elegant forms and high-quality instruments to refined orchestral, wind, and percussion instruments and pianos, we support the performance excellence demanded in every scenario — portable and electric guitars and amps, speakers that draw out sound dynamically, and many other audio devices all require premium sound quality. There is a growing trend in increasing product value-added features, and the diversity of power supply design needs is increasing. Accordingly, continue to rise annually. Particularly for the high-quality Products required in Japan, we continue to evolve and strive to meet those demands every day.

We also comply with the IEC62368 technical standards, which became the new unified standard. Due to the infrastructure development driven by the 2020 Tokyo Olympics (such as stations, ward offices, libraries, hospitals), regular replacement of Olympic-related audio equipment, IoT-related devices (like audio surveillance equipment), and industrial machines (robots, audio advertisement displays, and more), there is a wide variety of areas for which the AC/DC Power Adapters — Desktop & Wall-Mount from UNIFIVE can be useful. We will continue to support people's lives with our power supply solutions as a foundation of future technology.

We are confident that we can offer proposals that meet your Products requirements, so please feel free to with any requests you may have.

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