I've read the LM380 amplifier data sheet and application notes, and they show a power supply ripple rejection number that's based on the size of the bypass capacitor. There are also a few designs that use trimmer potentiometers into the bypass pin. Other than that, there's no actual mention of what this pin does or what the requirements are. (This is pin 8 on the DIP-8 package, pin 1 on the DIP-14.)
Here's the data sheet and application note link: http://www.ti.com/product/lm380
The data sheet also talks about a 100 nF decoupling capacitor on VS / GND, as usual for most ICs. But what is the bypass pin really for? Will the voltage ever swing negative, or can I use a regular electrolytic/tantalum on that pin?
Here's my proposed circuit (I'm learning KiCAD, so it's not all that great; apologies in advance for the vertical labels!) if it helps answer the question:
Also, regarding capacitor polarity: I'm assuming the output AC coupling capacitor can be a regular polarized capacitor, even though the charge of the capacitor and inductance of the speaker will temporarily reverse the effective potential when the output goes close to ground in a waveform swing?