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The difference between a pure power amplifier and a preamplifier

Release time：2021-11-09

A pure post-stage amplifier is a simple volume amplification, which requires the amplification and control of the pre-stage. A pure post-stage amplifier only has the amplifier part. It is convenient to match with various pre-stages and has a large upgrade space. A pre-amplifier is a complete amplifier that combines the pre-stage and the amplifier stage into one. Ordinary amplifiers usually have 20dB pre-stage amplification or tone, volume, etc., and have multiple inputs; a pure post-stage amplifier is only responsible for power amplification, and at most only has volume adjustment, and the inputs are generally 1-2 groups.

It can be said that the pre-stage makes sound, the post-stage outputs, the pre-stage is the leader and the post-stage is the bottom. It is actually possible to use a pre-stage without a pre-stage. You can also install a volume potentiometer to control the volume in the post-stage. However, adding a pre-stage is not only used to control the volume, but the effect will be worse under the same conditions. It is difficult to say that the input impedance of the post-stage of the power amplifier is completely matched with the sound source. The input impedance of the power amplifier is often too small. Some sound sources cannot drive the power amplifier. At this time, the pre-stage must be used for impedance matching.

In addition, the pre-stage can be added with a tone circuit to make a tuning pre-stage, an amplification circuit, a pre-stage amplification, etc. The pre-stage is not necessary, but the manufacturer adds a pre-stage in order to match various sound sources. AV amplifier matching is one reason, and the other is to add a pre-stage with multiple functions in order to integrate tone, input selection, phono amplifier, etc. in the power amplifier. There are also a few uses to meet the special needs of some people, such as "polishing" of the tube pre-stage, tone circuit, electronic frequency division, etc.

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