Audio amplifiers in mass production typically use an integrated circuit to amplify the audio signal. Even though modern audio amplifiers reproduce audio signals with less signal distortion than their predecessors, some audiophiles prefer the "warm" tone a tube amplifier produces when it reproduces an audio signal. Except integrated circuit to amplify, many audio and power amplifiers sold for personal and commercial use contain electronic devices called transistors. Transistors came about as an intended improvement upon an older technology—the vacuum tube, used as an amplifier component since the early 1900s.