Excellent amp for upright bass and players who double on DB and slab. Two inputs channels so you can set each just right for each instrument. Clear and clean. You know the AI story. Super reliable, clean uncolored sound, high power output, lightweight, great features and exceptional customer service Owners manual http://www.acousticimg.com/assets/docs/manual-series4.pdf This two channel 500 continuous watts (at 4 ohm) model has reverb and effects for both channels and also Hpf. Dependable power in a lightweight class D amp. Inputs for each channel accept both XLR and 1/4 inch. Output DI features are very useful. Full range frequency response: 20 hz to 20 Khz. All features work. A few minor scratches but no damaged knobs or connections. 500 watts of clean power at 4 ohms. Handles 2 ohm loads very well and for hours. All four original feet are there and in great condition. Includes AI amp bag with strap. And power cord. $449 shipped conus. PayPal ok.