What should I do about interference caused by radio noise?

With the advancement of technology, it has become common to live in an environment surrounded by radio waves. This page introduces measures against electromagnetic noise for AC/DC Power Adapters — Desktop & Wall-Mount.

Solving noise issues is a very challenging problem.

We propose the following as countermeasures for interference caused by radio wave noise.

Noise Countermeasures for AC/DC Power Adapters — Desktop & Wall-Mount

We have received numerous questions from customers asking how to deal with interference caused by radio wave noise from AC/DC Power Adapters — Desktop & Wall-Mount.

Although we refer to it in general as "noise", there are various defined requirements such as communication-related noise and acoustic-related noise. Here, we would like to illustrate an actual example of a special type of acoustic noise called "Beat Noise".

Beat Noise refers to noise that appears as slanted stripe patterns during image reception of analog television signals (wavy noise, interference sine waves, etc.). In other words, on concert stages with large speakers, guitar amps, etc., when connecting two or more such devices, even before any sound is produced (in silent state), a howling or high-pitched noise may emerge from the speakers — this is that kind of noise.

Such phenomena occur when noise from the power source flows into the speakers, resulting in disturbing noise sounds. Usually, this is considered to be caused by loop connection of the GND of the AC/DC Power Adapters — Desktop & Wall-Mount and the GND of the signal connection. Measures against causes such as insufficient gain or interference between carriers are often challenging.

Currently, Unifive is developing custom solutions for customers in the audio equipment industry, and we have adopted the following design improvements to resolve this issue.

① Separate the GND connections between the primary and secondary sides of the AC/DC Power Adapters — Desktop & Wall-Mount

② Add ferrite beads to the internal ceramic capacitors of the AC/DC Power Adapters — Desktop & Wall-Mount

Implemented as shown in the reference photo below.

③ Modify the pin connections of the internal transformer of the AC/DC Power Adapters — Desktop & Wall-Mount

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

You can compare the measured waveform diagrams as a result of the above improvements.

By applying this countermeasure, if the waveform level (peak value) decreases and becomes closer to a sine wave, low-frequency audio noise can be reduced.

The output specification after implementing the above countermeasures is 13.0V/4A. These products are favored for use with guitar amps and the like.

At Unifive, we have extensive experience working with numerous customers in the audio equipment industry. We have a wide range of experience in developing custom AC/DC Power Adapters — Desktop & Wall-Mount with noise countermeasures, including design principles that meet the IEC60065 audio safety standard, methods to improve acoustic noise from 6dB–12dB, component selection aimed at longevity, support for static discharge, and high customization demands (e.g. gas corrosion resistance of metal pins, Beat Noise countermeasures).

The audio equipment market is adapting to the digital age. From elegant designs and instrument-like quality to refined orchestral/percussion/piano equipment, high-level sound quality is demanded in all scenes — including portable/electronic guitars and amps that provide excellent performance, as well as speakers that draw out dynamic sound. As product value continues to rise, so too do diversified demands for power supply design; inquiries are increasing year by year. For high-quality Japanese electronics in particular, we are evolving daily to meet these needs and striving to provide excellence.

We also comply with the new unified technical standards of IEC62368. Additionally, infrastructure development related to the Tokyo 2020 Olympics (stations, ward offices, libraries, hospitals, etc.), regular replacement of Olympic-related audio equipment, IoT equipment (monitoring/audio systems), industrial devices (robots, audio ad signboards), and more — all require wide-ranging solutions. We at Unifive are committed to ensuring that our AC/DC Power Adapters — Desktop & Wall-Mount can be used in all such fields, supporting the technologies that enrich people's lives from the power source.

We are confident that we can propose solutions that meet your product requirements, and we would be most grateful for any inquiries you may have.

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