Hi Dave,
I have a fascination for model sound (and light and animation). I spent some time deconstructing a JJC unit to understand how it worked - the answer is incredibly simple compared to some modern cards.
As you probably know it was based around an APlus aP8821 OTP (One Time Programmable) audio chip giving 21 seconds of audio @ 6khz which by modern standards is really low tech - maybe that's why it sounds so good(?)
A simple Pic chip interfaced to the radio control receiver input and the audio was output to a Philips TDA8945S single-channel audio power amplifier with an output power of
15 W at an 8 W load and an 18 V supply. From what I understand it was the amp that was the weak point as it often overheated and died
This combination does produce a particular sound that doesn't seem to have been replicated with more modern sound devices
At some point when I have time it is my intention to see extract the audio profile from the chip and analyse it's characteristics. With modern DSP boards some really amazing sound can be produced.
I have had the board below sitting on my shelf waiting time to fire it up for model sound - I believe it will knock spots off most model sound having used it's little brother in the past
All part of the fun....
C-3PO