I have gotten Wayne, NB6M's Minima hardware working with a rotary encoder, thanks to the great work by Eldon, WA0UWH. Eldon has come up with a clever way to implement an encoder on top of his button structure that only requires a single input pin on the ATMega328 to handle all 7 buttons, plus the rotary encoder. Check out his blog for all the details.
I am sitting here listening to 75 meters tonight to the group that meets around 3.885 MHz on AM. Most of these guys are running old AM ham gear.
I have replaced the audio section with an LA4425 power amplifier chip. This is a 5W amplifier that typically is found in a automotive applications. It requires very few external parts and has sufficient drive to comfortably drive an unpowered speaker.
I have inserted this circuit between the volume control wiper and the speaker. Here is a shot of the ugly-style build in Wayne's Minima.
I like the end result, but it actually has a little more gain than it needs for this application. It is nice not needing to use amplified speakers just to hear the radio. I have not yet screwed down the component. It runs cool enough in this application, but the additional heat sink couldn't hurt.