It was in a box marked 'Amplifier & pre-amp boards ~ circuit diagrams in filing cabinet'. I know nothing more about this, but if you are reading this you will probably know all about it and its uses.
Sound Leisure D4 4-Channel Digital Jukebox Amplifier Module Amplifier
Hacker Radio Audio Amplifier A209 From A Hunter RP38 Also Found In Other Models
Joblot of Misc Sound Leisure CD Jukebox Parts, Amplifier Audio Parts, Keypad etc
Double 2 RCA Male to 2 RCA Male Stereo Audio Cable For TV, Amplifier, Speakers
