Er...why do you want to do this? Equalizers really should not be necessary (excepting something time-domain based like the Audyssey, which is different). EQ is generally used to try and patch up problems in the system/room...but those problems often cannot be fixed by an EQ!
And yeah, you would need pre-out/main-in jacks or processor loop jacks. What receiver do you have? Picture of the back panel? Also, what EQ do you propose to use?
I still have dbx dynamics and BBE processors on an analog input to my AVR to be able to 'fix' problems with an occasional older cassette/VHS tape, or sometimes a really dreadful mastering job on a CD/DVD (usually something that was originally a badly mastered tape then a botched transfer to disk!)
The external EQ idea can work with a modern receiver depending on what your goals are. It will not work to modify anything but the analogue pre amp signal paths. You really can't use it for 5.1 or 7.1 theater modes. That's better left to the receivers internal EQ features. Here is what I did. I have a pair of Cerwin Vega CLS-215 towers that I use for 2.0 music and are not used in my 7.1 theater. I use my receivers zone 3 pre amp, which has no internal provisions for equalization. The pre amp signal runs to a DBX1231 EQ. Then to a CV-2800 amp. The EQ is overkill for most having 31 bands per channel and being able to boost or cut up to 15db. It works great for my application, but most would not bother with this.
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