When searching for the "Kenwood Amplifier A-5j Manual," you will encounter two distinct documents. You need to know which one you require.
The rear panel of the A-5j is more complex than modern AV receivers. The manual explains the difference between "Direct" coupling and "Capacitor" coupling for pre-out/main-in connections. Connecting devices incorrectly could send DC voltage into your power amplifier, destroying both the amp and your speakers. The manual provides the exact wiring diagrams. Kenwood Amplifier A-5j Manual