Internal and external effects on a mixer refer to the different types of audio processing that can be applied to a sound signal. Internal effects are those that are built into the mixer itself, such as equalization, compression, and reverb. External effects, on the other hand, are effects that are added to the sound signal after it has been mixed, such as delay and chorus.
Internal effects are typically controlled using the mixer's onboard controls, while external effects are added using external hardware devices or software plugins. The use of internal and external effects can help to shape and enhance the sound of a mix, allowing the engineer to achieve a wide range of sonic possibilities.
Internal effects can be particularly useful for making quick adjustments to the sound of a mix, as they are easily accessible and do not require additional equipment. However, external effects can often provide a higher level of control and flexibility, as well as a wider range of options for processing the sound signal.
In general, the choice of whether to use internal or external effects will depend on the specific needs of the mix, as well as the preferences of the engineer. Both internal and external effects can be valuable tools for achieving a professional and polished sound.