Noise band, any reason why past it?

Question (example): The noise is given in the audio band. If a 5V power supply is used to power a USB DAC how much significant can be the noise beyond the audio band?

Answer: This depends a lot on the design of the DAC itself.

Actually, the high-frequency noise in the iPower is also really low. Generally, the noise floor above the audio-band is lower than the audio band noise, which is one of the reasons we only specify audio band noise.

There are some noise components from the switching frequency (at around 100kHz). With generic SMPSs & Chargers 0.03V RMS (or 44dB below 5V) noise are common. By comparison in the iPower, this noise is guaranteed to be below 0.00001V RMS (or 114dB below 5V).

Indeed, many regulator ICs used for audio have a greater audio band and high-frequency noise than these 0.00001V from the iPower. Hence normally the levels of high-frequency noise remaining in an iPower should be low enough to have no consequence whatsoever on a USB DAC (or any other Audio Device), even one that has only minimal or no built-in power supply filtering/regulation.

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