I have an older Yamaha RX-V567 and Polk Audio Center, Sub and 2 Tower speakers currently connected using the larger output speaker jacks. I want to connect a Rockville EQ that has only RCA jacks. I've tried a couple of combinations but it doesn't work. How can I connect and programme it to use the Rockville EQ? I would rather not use the onboard 5 channel EQ that they say can be set up with the unit. The Rockville is Dual 2 channel 10 band with RCA input and outputs. I just need to know how to get this to workwith the Yamaha.
Your Yamaha has no connections that will allow you to use any EQ except to connect one channel of it in between the sub out on the AVR and input of the subwoofer. EQ can help but has to be used sparingly with not more than 3-6db of boost. It won't make a bad speaker sound like a good one but it can make it a little bit better. It can also be used to correct for room issues.
The other more costly option would be to connect a speaker to line level converter to the front speaker outputs. Then you would connect that to the input of the EQ. The output of the EQ has to be connected to an external power amplifier to drive the front L/R speakers. The EQ will only affect those speakers.
Use the internal EQ of the Yamaha. The center and surrounds would need different settings than the LR front anyway.