The decision was made to make another audio recorder out of the Generalplus dongle, because there's no way of knowing which one is better without building 2 completely functional units.  

The Generalplus has a setting for monitoring the mic, but it's an inaudible level, so you have to make a software loopback.

Full duplex playback does work, because it's designed for a headset.

The Generalplus only takes stereo for playback.

Using aplay & arecord to monitor the microphone creates too much latency.

Using libasound directly creates less latency, but still an unacceptable delay.  Getting acceptable latency requires reducing the record buffersize.  At 512 samples, there are lots of playback underruns, but recording hasn't overrun yet. Making the playback buffer bigger than the recording buffer is unacceptable, since it would increase the latency. Latency was an unsolvable problem with the CP33 project.

Installing another board to monitor the mic in hardware is now the only option. If it only amplifies the General's output, it needs to be tested for the noise penalty & playing files would then always be noisier.  If it amplifies directly from the microphone input & mixes in the general's output, it's exactly what was done before for phone headsets.  It's a less compact board & requires turning a pot but is still far smaller than the AK4524.  That web interface may be overvalued & filled with buzzwords, but it's a lot more convenient than turning pots.

The 3rd option of boosting the mic signal enough to hear it from the general's monitoring path would add too much noise to the recording.