Think of it as a chain, starting at the back, you disconnected your rcas from your amp. Now there is nothing before your speakers to cause noise EXCEPT your amp. No noise means amp is not the issue. Now plug your rcas back into the amp (NOT WHILE SYSTEM IS TURNED ON, PLEASE) and unplug them from your converter. check for noise. No noise means noise not being introduced into rca cables. Power down, plug cables back into converter, disconnect speaker inputs from other side, ect, ect you get the point. If you are using the signal sensing turn on for your converter, you will have to power it main line when the speaker leads are disconnected, or it wont power up, and the remainder of the testing will be mute.
If all this leads to no help, drop your gains on that converter, and set them on your amp with a multimeter. You may be shoving that noise down your amps throat with too high of an input voltage.
Way too much info before bed. lol