You can connect the EQ to preout2 and main-in, subwoofer to preout1. The EQ will only effective to your main speakers, no effect to the subwoofer. If you want the EQ control subwoofer as well, a pair of ’Y’ connector will be needed.
https://encrypted-tbn0.gstatic.com/images?q=tbn%3AANd9GcSs3yzyzYMrWNF0fP65Q4_uRjhNGwPPS2hy3449L3lYAE...
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