Quote Originally Posted by David Analog View Post
A line output convertor can definitely degrade audio quality. Some, not all, amplifiers can process a speaker level HU output without such a convertor, whether by having separate high level inputs, or a selectable RCA input level with a differential input. If you need to add something external, use a dual line driver controller, like the Kicker or two JL Audio. These items will give you the dual zone control less expensively than an EQ and in a cleaner manner than an EQ by not extending the signal path with long to and from RCA cables. Also, these components give you dual zone control at your fingertips with the smallest possible footprint....just two small rotary controls.
Listen to David. That converter will make your signal worse. Don't do it. They make cheap zone controllers like David said. That would be okay.