What it is:
The ISO Line Out box is used to provide a transformer-isolated signal from any guitar amplifier speaker ouput jack. One common purpose is to provide a line level signal that feeds an effect processor. The wet only output of the effect can feed another amps effect loop return or power amp with speakers to have a Dry/Wet setup or even Wet/Dry/Wet.
What it is NOT:
The ISO Line Out box is NOT a load box. In other words, the amplifier MUST have a speaker connected at all times. The ISO Line Out box is not a speaker cabinet emulator.
Connect any available speaker output jack to one of the Speaker Thru jacks on the ISO Line Out box. If the amp has only one speaker output jack, connect this to one of the Speaker Thru jacks on the ISO Line Out box and plug the speaker into the other Speaker Thru jack. Connect the Line Out jack to a balanced or unbalanced jack of your mixer, effect or recording device. Set the appropriate level.
The Line Out jack is wired for balanced or unbalanced connections. The transformer is wired to the tip and ring connections of the jack. The cable shield is floated and can be referenced to the box ground ONLY when a balanced cable is used.
The phase switch is used to invert the phase of the signal. Set the switch in the up position to invert the phase, down for normal phase.
GND Ref Switch:
The ground reference switch can be used to reference the box ground to the Line Out cable ground. This should ONLY be used with the use of a balanced cable. For mono cables, leave this switch in the down position.