Encoder bandwidth limitation
 

Does the encoder implement automatic bandwidth limitations, lower sampling rates, at low bit rates?

Hi. Yes, at quality settings lower than 5 (which is --standard), the maximum bandwidth is lower than 20 kHz.

At --quality 7 it's 22 kHz, --quality 5: 20 kHz, --quality 4.5: 17.9 kHz, --quality 3: 13.1 kHz, etc.

You can view verbose encoder details by adding --verbose to the command line. (mpcenc --verbose input.wav output-customname.mpc)

What is the bandwidth on the lowest setting?

The lowest setting is --quality 0.1 and its maximum bandwidth is 5.5 kHz.

dbpoweramp, unfortunately, does not encode in mpc.