Summit Audio EQF-100 by Paul Ryan
When looking for a good EQ, I already was familiar with Summit gear so purchased a used Summit EQF-100. This is a single-channel 4-band unit with high and low pass filters. Each of the bands has seven selectable frequencies, and the filters each have three frequencies. I have found that this setup allows for a whole lot of flexibility, you can zero in on pretty much any area you would like to. I don't believe they are manufactured any more but sometimes you see these on eBay. Mine is from the late 1990's.
While it might not common practice, I use my unit during tracking. My material is acoustic country and I am always searching for "warm" sounds for ballad-y stuff, and sharp focused sounds for uptempo. So I don't use the EQF-100 during mixing or mastering, leaving that instead to my producer (who noted recently he hardly ever adds eq to my tracks). At any rate, with that all said I absolutely love this unit, can't say enough good things about it.
Since tracking with EQ can be touchy it took me a while to get comfortable, but now I cant imagine not having mine in the rack. There are so many applications, I cant cover them all here. But a couple examples are: taming the thin upper frequencies in my TLM 103 mic so it sounds absolutely beautiful; "riching" up the lows in my baritone guitar (actually probably any instrument);tucking in frequencies for a lead instrument in songs that contain repetitive arpeggios etc., and so on. Pretty much if a particular sound isn't to liking or on mark during pre-recording practice sessions, the EQF-100 gets busy. I understand these are older units and not for everyone. But initially when I bought it, I thought a single track is all I need, but now, I am actually thinking of getting another one. If you find one in good condition, I'd highly recommend it.