An audio device for amplifying an audio signal enables a user to instantly switch between two or more active amplifying components, thereby allowing the user to evaluate the effect of a particular active amplifying component in the audio device. In one example, the audio device is an audio vacuum tube preamplifier, and has a circuit configuration that facilitates A/B comparison between two or more preamp tubes by hot switching between preamp tubes in the audio signal path. The input to the two or more tubes is switched between each tube by the listener on demand without pause or interruption to the music or program.