I can't say specifically with the Torii Jr, but I have a sub connected to my UFO25, using high level connections. I'm not sure if the Torii is the same, but the Zen UFO amps have floating outputs that are not connected to ground. So when connecting my sub, I had to use a cable to bridge the negative output connections on the amp to prevent hum. Otherwise, there was loud hum. When properly connected, it sounds great!