Thank you for the kind words! So that is actually not a button, it's a small 2 port USB plug.
The Amp/Volume Control is actually in the top part of the arcade, under the "Arcade" logo. That part is hinged and I can open up and adjust the volume

https://www.amazon.com/dp/B07SQ17LS2/ref=cm\_sw\_em\_r\_mt\_dp\_B8TB8SZFHM35WWS48SSA