I got few pairs of ECHO Sound Synthesizer -card speakers awhile ago and started to look for the interface card as well as one did not come with them.
Luckily i was donated pair of cards (thanks Will!)
“ECHO”-speakers. Is there reason for different color of the button?
-Echo 2+ (have mono and stereo outputs)
ECHO+ installed to my “main” Apple //e platinum.
Video of the “Alien Clonepure” & ECHO+ sounds:
Found this image from the internets, so this is how the retail package have looked like.