How do I increase sample rate of recordings made by Asterisk

Hi, I’m currently using MixMonitor to record two channels and no matter what I do, I can’t seem to increase the sample rate above 8Khz. It looks like MixMonitor supports wideband recording (here: yet I can’t make it work.

Any ideas on how to make a wideband audio recording with Asterisk? I’m open to using other applications such as ConfBridge or Monitor. I would love to make recordings at 48kHz if possible since the channels themselves are using wideband codecs.