ProtoDAC TDA1387 X8 project

[hifinet]

For my current setup, it would go between the SMPS and the Kali. These DC filters attenuate noise, but they don't eliminate it. People have used multiple filters in series. But then you are affecting the transient response of the power supply. It would be best to filter, then go into a capacitor or ultracapacitor reservoir.

There is still noise generated by the Raspberry Pi CPU and also the switching regulators of the RPi. Only the original RPi 1 had linear regulators. Some people would actually do microsurgery on RPis with switching regulators, and replace with linear regulators.

That noise from the SMPS gets everywhere. Not only on the positive line, but in the grounds and radiates back onto the AC line. Some EMI as well, but much less significant. Electronics need to pass EMI standards set by the FCC and European regulators.

Until I heard the 5V ultracap supply of the PurePi, I didn't fully appreciate the haze of noise that the Allo basic 5V SMPS was casting, even with the built-in filter of the Kali. I knew there was some noise, but didn't realize it was that much. For some reason, the Allo SMPS creates a larger soundstage, so it has that benefit in its corner. The LifePO4 battery and/or ultracap supplies plus isolation (to deal with the noise from the RPi) seem to be the best solutions.