There are all kinds of great techniques in using the boost and attenuation simultaneously on an EQP-1A (or emulation). The passive circuitry interacts in ways which allows a whole range of control over the frequencies which are not apparent.
Let’s take a look at a few of these below, using the UAD Pultec EQP-1A plugin as the example. (Any accurate emulation will work in this same way, although there will be slight differences in the settings among different companies. Just as an aside, poor implementations will show much steeper responses and the curves will be less smooth, probably because they are simply utilizing standard EQ algorithms and packing them into a EQP-1A looking interface.)
Let’s look at the first two “charts”, which show the way this technique is usually used and illustrated. The boost and attenuation are set so that the low end is left untouched (!) but there is a drop in a more specific frequency range. The low frequency knob lets you adjust where this “scoop” takes place without touching the boost or attenuation.
This is the most well-known “trick” and it is tricky. The smallest adjustment to either the boost or attenuation will nearly eliminate the “scoop” effect and raise or lower the low end. Graphing this is a good way to understand what is happening and I have a preset created for myself with the balanced settings, because my ears are just not good enough to always discern the precise setting. Load the preset, and adjust the Low Frequency knob!
That is the “famous” technique, this one is less so. By attenuating both the low and the high (the low end boost is set to 0), you can create a nice smooth boost in the mids. The only change I show below is the high frequency (“ATTEN SEL”) setting.
Now some even less intuitive settings. Below you basically have a flat frequency response, although the knobs are all over the place.
But just make some minor adjustments and get some subtle changes for shaping a sound. The first is clicking the high frequency setting, the second is clicking the low frequency. Also, notice the second is identical to the frequency curve in Chart 2B, even though the setting are completely different!
Just a couple more examples to inspire you!
All of this and we haven’t even touched the high frequency boost control! You may be asking, “why would I use this when I can just dial in whatever EQ I want with some “modern” plugin, and even see what it is going to do right on the interface?”
First of all, the EQP-1A is incredibly smooth without using any of these techniques. Just attenuating the low end creates a subtle shelf that is super easy to dial in. The same with the high end.
Secondly, if nothing else it allows you to get a feel for what you are doing in a very unique way. It engages your ears. You might also ponder “the old days”—if this was your only way to EQ, your recording methods and techniques would certainly emphasize getting a good sound to begin with.
But this isn’t about trying to convince anyone to use some specific EQ, it’s about encouraging curiosity and the desire to try things for yourself. Use whatever works best for you, but spend a little time playing with your EQP-1A emulation and having some fun! (Of course, if you have a real one in your rack I’m pretty sure you are using it on every project.)