How to suppress hum on the LINE output of the Torpedo Captor ?
The LINE output of the Torpedo Captor is balanced. When connected to a balanced input, with a balanced cable (a cable with 3 connections), what you get is a balanced connection, which is highly immune to hum, noise, and other kind of interferences.
A balanced 1/4" jack connectors is called a TRS jack connector (which stands for Tip, Ring, Sleeve, representing the 3 parts of the connector). You may know this connector as a "stereo" connector, it is the same connector.
To get a balanced connection out of the LINE output of the Captor, you have to use either a 1/4" jack cable with TRS connectors on both ends, or a cable with a TRS 1/4" jack connector at one end and an XLR at the other end. You also have to connect to a balanced input. This could be a Mic or Line input. High-Z or Instrument inputs are usually not balanced.
The Input of all the Torpedo products (including the Torpedo C.A.B.) is balanced, so when using the Captor with a Torpedo C.A.B., just use a balanced 1/4" jack cable.
If you can't connect to a balanced input, typically if you want to connect the Captor to a standard guitar input, and you get some bad noises or hum, there is a way around. You can use the XLR DI output of the Captor. You'll have to provide a power supply to the Captor, and use an XLR to 1/4" jack cable. This time, an unbalanced 1/4" jack connector is needed (aka "mono", ie the standard guitar connector).
The output circuitry of the DI output of the Captor is different than the LINE output. It takes advantage of the power supply to actively balance the signal inside the unit, and then the output buffer makes sure everything is OK even when used unbalanced.
If applicable, don't forget to set the SPKR SIM switch to OFF, to get a dry sound out of the DI output.