Generally speaking, it is a better idea when setting a graphic equalizer for the desired "boost" to merely do the opposite, "cut"!
That is, instead of boosting the area of interest, decrease all the other bands
to form the desired curve.
The reason for this is that an EQ of just 6dB results in a significant increase of voltage - often this will cause a rig to overmodulate, OR the following stage to be overdriven. By decreasing the sliders, you can create essentially the same curve, without increasing the peak levels sent to the rest of the signal chain and/or the speech amp.
For most transmitters you can not modulate over 100% without hitting the baseline on the negative peaks. In the case of say a DX-100, Apache or Valliant where the finals are 6146s with ~750vdc for the B+, that means that the modulator can not swing more than +/- 750vac peak
without overmodulating the rig!! If you set the modulation level from the speech amp so that you just are at or below 100% modulation - ie. the swing is +/-750vac of audio to the plate of the finals - and then apply 6dB more input signal you've just tried to add 4x the voltage swing!!
Therefore this maximum "safe" modulation level (voltage) corresponds to a specific input voltage
at the input to the speech amp (for a given signal chain gain). If you boost the EQ sliders (or knobs), then the level sent to the rig is increased, albiet only for the frequencies those sliders boosted, but that means that the gain on the rig (speech amp) has to be reduced in concert. Whereas, if the rig is set so that the rig is properly modulated with "0" level on the sliders (knobs) of the EQ unit, then by reducing the sliders downward
below "0" you are assured of not overmodulating
no matter what EQ you have applied!
The difference between cutting and boosting to achieve a desired curve is mostly in the mind, electrically the audio doesn't know the difference in terms of how it sounds...