The BSS AR-133 is an active direct injection (DI) box and line balancer designed for professional audio applications. It's known for its rugged construction, high-quality audio performance, and versatility. The AR-133 can handle various input signals, including those from instruments, line-level sources, and even speaker outputs, thanks to its switchable input attenuation. It can be powered by phantom power or a 9V battery, with automatic switchover to battery power if phantom power is lost.