This is a guitar/harp amplifier made from a Webcor model 2103 reel to reel tape recorder. tubes are; 12ax7, 12au7, 12au7, 12ax4, and 12ab5. there is a TRS jack in the back of the amp for an extension speaker. When an extension speaker is plugged in the amp's speaker is off. This is a low power amp with good breakup and sustain. Schematic diagram included.