The main amplifier is shown in the upper shaded box.

In 2011 he continues to use Fuchs Audio Technology as his main amplifier.

Auto-zero amplifiers use a secondary auxiliary amplifier to correct the input offset voltage of a main amplifier.

Another problem associated with headphone sockets on main amplifiers is that a series resistance is inserted between the phones and the output stage to reduce signal levels.

Figure 7 shows the small-signal schematic with the main amplifier and the feedback two-port in shaded boxes.

Figure 7 shows the interesting fact that the main amplifier does not satisfy the port conditions at its input and output unless the ground connections are chosen to make that happen.

Distortion circuits distort a signal before it reaches the main amplifier.

Overdrive circuits do not create distortion themselves but rather boost signals to levels that cause distortion to occur at the main amplifier's front end stage.

Donovan's main amplifier is a Vox AC30 used in combination with vintage Fender amplifiers.

Most other subwoofers take their driving power directly from the stereo system's main amplifier or receiver, without interposing a special booster amplifier.