The difference between a pure amplifier and a preamplifier

A dedicated power amplifier is a simple volume amplifier that requires the amplification and control of the preamp. A dedicated power amplifier has only the amplifier section. It is convenient to combine it with various preamps and has great upgrade potential. A preamp is a complete amplifier that combines the preamp and power stages into a single unit. Conventional amplifiers typically have a 20 dB preamp gain, or tone and volume controls, and have multiple inputs. A dedicated power amplifier is responsible only for power amplification and has at most only one volume setting, and the inputs are usually divided into one or two groups.

It can be said that the preamp produces the sound, and the power amplifier provides the output. The preamp is the guide, and the power amplifier is the foundation. It is actually possible to do without a preamp. You can also install a volume potentiometer in the power amplifier to control the volume. However, a preamp is not only used to control the volume, and the effect will be worse under the same conditions. It is difficult to say that the input impedance of the amplifier's power amplifier is completely consistent with the sound source. The input impedance of the amplifier is often too small. Some sound sources cannot drive the amplifier. In this case, the preamp must be used for impedance matching.

Additionally, the preamplifier can be equipped with a tone circuit to provide a tuning preamplifier, a gain circuit, a preamplifier, and so on. The preamplifier isn't mandatory, but manufacturers add one to accommodate different sound sources. One reason is to match AV amplifiers, and another is to add a multi-function preamplifier to integrate tone controls, input selectors, phono amplifiers, and so on into the amplifier. There are also some applications to meet specific needs, such as "polishing" a tube preamplifier, tone circuits, electronic frequency separation, and so on.