We use this hooked up to an 8-ohm monitor speaker to let people demo pedals.  This amp just plain rocks.  Lots of head room.   It is a 22 guitar head in a box the size of an effects pedals.  Works with 8 or 16 ohm.  Has a bright a switch to boost your signal.  It can even be pushed into overdrive for a little grit!  Includes 18-volt, 1.6 amp power supply.