The Denon would have to have a tape monitor switch in order for it to equalize all sources. Sort of. They quite putting tape monitor loops in receivers back in the days of Dolby Pro-Logic. If you recall, DPL was an analog-based surround sound processing protocol, but pressing the Tape Monitor switch would revert your surround sound program to two-channel stereo. The loops aren’t compatible at all with modern digital signal sources – two completely different signal paths.
If you want to EQ all sources, you need to connect the equalizer between the Denon and your amplifiers. Assuming it has enough headroom to be used like that. If it clips, your only option will be to get pro-audio equalizers.
Regards,
Wayne A. Pflughaupt