Info from Beavis about the amp:
More information can be found on the Beavis Audio site here.
Added optional headphone output daughterboard. Don't forget to use a stereo socket for the headphone output and it will need to be a plastic body type socket, so the sleeve can be isolated from ground through the box:
And a switched headphone option. An easier way of doing this would be to feed a switched headphone socket from the daughterboard, and the signal also going through the normally closed contact to the speaker output. Then when a plug is in the headphone socket, the speaker will be diconnected automatically.