Hi, basically I want to build a very very simple bass amp on a protoboard for a project with the speaker included that is portable (so powered off small batteries). I was thinking of using a design similar to the below, but I don’t know what values of resistors and other components to use, also if I did use 12 V power supply I wouldn’t want the op amps to saturate so I going to have 2 limit my gain quiet considerably. And how would I get the – 12 V off one battery? Would I need 2?