The following are appropriate connections when using the "four-cable" method setup with the GT-100:

- Connect your guitar to Input of the GT-100.

- Connect the Send of the GT-100 to the input on your amp.

- Connect the Send on your amp to the Return on the GT-100.

- Connect the Output on the GT-100 to the Return on your amp. 

After making the connections, be sure to turn on the SEND/RETURN loop in the GT-100:

1. Press the EFFECTS button. 

2. Turn knob 4(SELECT) to choose the "S/R" icon. 

3. Turn knob 3 to turn on the Send/Return Loop. 

4. If desired, turn knob 4 to select the appropriate Mode for your setup. (For more details about the different S/R modes, see page 29 in the GT-100 manual).

5. To save the settings, press WRITE twice to and store them to a User patch location.