Understanding Amps in Technical/Modifications Posted March 13, 2009 Boy, where is everybody tonight? I guess they've all gone out. You forgot to ask what a SET is. Since the pros haven't answered I can tell you this much. A push pull has two output tubes per channel. A single ended amp only has one. These two different types of tube amps sound different. Also, some tube amps can switch between these two modes of operation. There are also hydbrid amps which have some tube and some solid state circuits. SET = single ended triode.