Zapco DC Intro - Manual (Page 22)

Voltage sensitive Equalization
Here is a great tool for the advanced Tuner/Installer
Each channel of the DC amps and of the DSP-Z8 has a parametric EQ band that
is only on …
when you need it!
30Hz boost …only on when you need it.
Example : You have factory radio that
cuts the bass frequencies at high volume.
You can set this band to restore the bass only when
you have high volume. In this case the Bass boost
begins when the signal voltage reaches 1.991V