I have a Teac PD-301-x FM tuner with excellent sound but only an analog RCA output from the FM Radio. So, to have its sound in my HiFi audio system, I added PocketADC into the chain, which looks like this now: Analog FM signal from Teac PD-301-X → PocketADC → SPDIF → Topping E70 Velvet (DAC) → Topping B200 (amplifier) → Dynaudio Emit 20 speakers. PocketADC is transparent, and now I can enjoy excellent FM Radio quality from my nice Teac tuner.
I selected 48 kHz as the sampling rate because the source signal is analog FM radio, which has a limited frequency range—typically up to around 15 kHz. A 48 kHz sampling rate comfortably captures the full audio bandwidth of FM broadcasts without unnecessary overhead. I did not see any heat from pocketADC. Also, I use a linear power supply, Keces P6, which also powers my Teac FM Radio component.