Vacuum tubes were the dominant active electronic components in bass amplifiers manufactured from the 1950s until the early 1970s. Tube amplifiers for bass almost always use class AB1 topology for efficiency reasons. Many bass players believe that tube amplifiers produce a "warmer" or more "natural" sound than solid state amplifiers when lightly or moderately driven, and more pleasing distortion characteristics when overdriven. Some performers also believe that tube amps have a greater level of perceived loudness for a given amount of amplifier power.