I built an amp for my sound chip, which is largely the circuit on this page, without R2, and with a small capacitor between pins 4 and 6 (GND and VSS), because without the capacitor there was a huge amount of hum, but with it it's almost silent. Now I don't have to connect it to my guitar amp any more. The next thing to do (with this circuit) is to build it onto the stripboard.