The audio chain is now complete and working. It consists of a 2N3904 serving as a preamp, which drives a single 2N3904 configured for unity gain to convert the single-ended output of the detector to the differential input of the LM386 amp. I may fiddle around with some of the filtering on the LM386 AF amp chip when the receiver is working, but it is basically done.

I have removed the variable capacitor for these photos to allow a better view of the circuitry.