EMI Suppression Filters (EMC and Noise Suppression)Audio line noise suppression for home audio:(2) Power supply line

Impact of the power supply on audio circuits and countermeasures

The quality of the power supply is important to output superior audio from an audio device.

Figure 1 shows the THD + N results when another device is connected to the power supply outlet of a home audio device.

We can see that while the THD + N deteriorates across the entire audible range when suppression is not implemented in the power supply line, applying suppression improves the THD + N result and the audio quality.

The PLT10HH Large Current Common Mode Choke Coils and BNX Series of Block Type EMIFIL® filters are effective for providing suppression from low to high frequencies in power supply lines.

Both series of products have been adopted for use in various sets to suppress power supply noise.

Suppression component:[Power supply line noise filter]

Figure 1 An example of noise interference from power supply circuits and countermeasures

Figure 2 Audio quality measurement results with power supply circuit suppression

Impact of audio circuits on the power supply and countermeasures

In many cases, power is supplied from an AC outlet for home audio, and the conductive noise in the power supply cable is regulated under EMC standards. Therefore, it is necessary to prevent noise from leaking into the power supply line during audio playback.

Methods of cutting the noise are generally introduced into the AC adapter or the ACDC power supply section, but it is easier to avoid the noise problem by applying suppression in the power supply section of the digital amplifier which is the source of the noise.

Figure 4 shows the results of measuring the noise leaking from the power supply line.

We can see that the higher harmonics of the digital amplifier switching frequencies are conducted as noise. Equipping the PLT10HH Large Current Common Mode Choke Coils and the BNX Series of Block Type EMIFIL® filters achieved an improvement of over 20 dB.

Suppression component:[Power supply line noise filter]

Figure 3 An example of countermeasures to deal with noise leakage from a Class D amplifier to the power supply circuit

Figure 4 Power supply noise measurement results before and after applying suppression products

Using the PLT10HH and the BNX products enables you to combine both suppression of noise interference from the power supply circuit to the audio equipment and suppression of the noise leaking from the audio equipment to the power supply.

List of power supply line suppression products