What should I do about interference caused by radio noise?

With the advancement of technology, we now live in an era where being surrounded by radio waves is the norm. This page introduces measures against electromagnetic noise from AC/DC Power Adapter.

Noise resolution is a very challenging issue.

We propose the following measures to address problems caused by electromagnetic noise.

Noise countermeasures for AC/DC Power Adapter

We have received many inquiries from customers asking what should be done about electromagnetic noise issues from AC/DC Power Adapter.

Although we refer to it simply as noise, there are various regulatory requirements, including communication-related noise and audio-related noise.
Here, we would like to present an example of a special type of audio noise called Beat Noise.

Beat Noise refers to noise that appears as diagonal stripe patterns when receiving analog television signals. (Also known as wavy noise or interfering sine waves.)
In other words, when connecting two or more devices such as large speakers or guitar amplifiers on a concert stage, a howling or ringing-type noise may be emitted from the speakers before any sound is produced (during silence).

In such cases, noise generated from the power supply flows into the speakers, producing unpleasant noise. This is generally thought to be caused by a loop connection between the GND of the AC/DC Power Adapter and the GND of the signal connection. Countermeasures for insufficient gain and interference between carrier waves are often difficult.

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

1. Separate the primary and secondary GND connections of the AC/DC Power Adapter

2. Add a ferrite bead to the internal ceramic capacitor of the AC/DC Power Adapter

It is implemented as shown in the reference photo below.

3. Modify the internal transformer pin connections of the AC/DC Power Adapter

Change the connection of the lead wire (black in the figure below) on the transformer core side from Pin 1 to Pin 2.

The measured waveform diagrams can also be compared after the above improvements.

By implementing these measures, if the waveform becomes closer to a sine wave and the level (peak value) decreases, low-frequency audio noise will be reduced.

The output specification with the above countermeasures is 13.0V/4A. These Products are widely used in guitar amplifiers and similar equipment.

UNIFIVE has extensive business experience with numerous manufacturers in the audio equipment industry. As a result, we have a wide range of development experience in AC/DC Power Adapter with customized noise countermeasures, including design philosophy based on the IEC60065 safety standard for audio equipment, methods for improving audio noise by 6dB-12dB, selection of components for longer product life, electrostatic discharge countermeasures, and responses to high customization requirements such as gas corrosion resistance of metal pins and Beat noise reduction.

The audio equipment market is adapting to the digitalization era of devices. From elegant designs and high-quality musical instruments such as refined wind, string, percussion instruments, and pianos, to portable electronic guitars and amplifiers that deliver exceptional performance in any setting, and speakers that dynamically project sound, high-level sound quality is required across various audio equipment. As product added value continues to increase, inquiries for diversified power supply designs have been rising year by year. In particular, for high-quality Japanese electrical Products, we continue to evolve and strive daily to meet these expectations.

We also comply with the IEC62368 technical standard, which has unified new technical requirements. In addition, with infrastructure development associated with the Tokyo 2020 Olympics (stations, ward offices, libraries, hospitals, etc.), periodic replacement of Olympic-related audio equipment, IoT-related devices (such as surveillance audio equipment), and industrial equipment (robots, audio advertising displays, etc.), there is a wide range of applications to address. We will continue striving to ensure that UNIFIVE's AC/DC Power Adapter can be utilized in all such situations. We support technologies that enrich people's lives through power supplies.

We are confident that we can propose solutions to meet your Products requirements. Please feel free to contact us with any requests.

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