Put it in the tape loop where it belongs. You'll destroy your S/N ratio by putting it between the preamp and amplifier. Why?
The average signal level sent from the preamp to the amp is very low. At normal listening levels, this signal is well under 100mV (0.100V). This is down in the gutter, as we consider the signal vs noise levels of the EQ device, and way too close to the noise floor of the EQ itself. But both this noise and that weak signal are amplified by the power amp just the same...most power amps have a fixed gain of about 20db, so consider that you have just raised the noise floor of the EQ device by exactly the gain of the power amp...not good!! If someone said, "Pssst! I have a device here, for free, that's guaranteed to reduce the noise of your system by up to 20db!" would you be interested? You'd be a fool not to be. And this 'device' turns out to be nothing more than the instructions to move four interconnect cables. :thmbsp:
Look at it as if you were setting the record level on a tape deck. There's a reason you record at the highest level you possibly can...your noise floor is fixed, and you're trying to elevate your signal level above this noise floor as much as possible without saturating the tape. This idea of keeping the signal level as 'hot' as possible to reduce the perceived noise when recording to tape is a perfect analogy for why you'd want to do the same thing when passing the signal through an external signal processing device, such as an equalizer...the noise floor is 'fixed', and we want our signal as 'hot' as possible through the device to reduce the perceived noise that is added by the device itself. This is a core idea in all signal processing, or else giant mixing boards in the recording studios wouldn't have banks of LED's or analog level meters to assist engineers in setting signal levels...if it doesn't matter, why bother with level meters at all?
This is why the equalizer should be added to the tape loop (tape monitor) connectors, as the unattenuated signal level there is MUCH higher (10~20db and more) than the weak signal that is passed from the preamp to the amplifier. Don't believe this? Connect the 'Tape Out' jack to the 'Main In' jack of the amplifier (OK, don't do this, as you'll probably drive the amp into hard saturation and blow the amp or your speakers or both).
And it's not like it's a secret....equalizers for home audio have tape monitor facilities built into them because they are meant to go into your tape monitor loop, and the monitor functions on the EQ are there to replace those that are lost by using the loop for your EQ device.
This is your equipment, and you should do as you like. But, the AK forums are not about listening to Soundesign or York other worthless BPC, we're into real High-Fidelity gear here and helping others to maximize their enjoyment while minimizing their investment. And although there's a right way and a wrong way to get many things done, sometimes there's 'a way that will work', and 'a way that works a lot better'. Tweaking your setup to get the highest possible performance out of it means finding 'a way that works a lot better'.
For an EQ, that means putting it in the tape loop, for the reasons I've outlined above.