This JBL UREI 6290 power amplifier is functional. Instead of knobs, it has caps in place.

To use this JBL UREI 6290 power amplifier, first make sure it's properly connected to your audio source and speakers. Then, turn it on and adjust the settings according to your needs. Remember, although it has caps instead of knobs, it still works well. When not in use, turn it off to save energy. Keep it in a dry and clean place to avoid damage. Also, don't expose it to extreme temperatures or humidity. If you have any issues, consult a professional.