Yes you can. It is perfectly fine, safe to run and won't damage the speaker in any way. But do note that this amp's speaker (the Eminence TT12/15) was designed specifically for steel guitar, so dynamically it will be much different than your typical guitar speaker. If playing an electric guitar through this amp, the speaker will bring out much of the high end, while the low end will be much more low and bassy-sounding.