You may wonder why the Pultec EQP-1A has separate knobs for boost and cut. The short answer is that they connect to different circuitry in the unit.
You can use the “extra” knob to your advantage. Because the filters are not phase perfect, a Boost setting of 3 and an Atten setting of 3 can make a huge difference, even though a frequency plot wouldn’t show much difference in tone. You’re hearing the phase shift, not the tone shift.
Our ears of very sensitive to phase, and using the two knobs together, you can adjust phase at the low end while also making tonal adjustments.
On the high end, you can set Boost to 10k and Atten to 10k, then adjust Boost and Atten simultaneously. However, because Boost is a peak equalizer and Atten is a shelving equalizer, the results are much different, and you don’t get independent control of phase.
In the high frequency boost section, the Bandwidth and Boost controls affect one another. This is different from modern equalizers, where adjusting Q typically doesn’t affect the amount of equalization applied.
Use caution, because the Sharp bandwidth setting results in up to 10 dB higher output than Broad bandwidth at maximum Boost, just like on the original. But don’t feel like you’re getting cheated. Consider anything that encourages very careful and infrequent use of peaky boosts to be a Very Good Thing.