A.The GR-20's GUITAR OUT jack only outputs the normal guitar sound, and not the synth sound. If you wish to hear both, use the OUTPUT R (MONO) and L (PHONES) jacks. (If your guitar amp has a monaural input, use only the OUTPUT R (MONO) jack.)
Next, you should set the GR-20's Output Select setting to achieve the best sound with a regular guitar amp:

On the GK-3's controller unit, set the Select switch to the MIX position. To achieve the desired balance between the normal guitar and the GR-20, use the GK-3 controller's GK Volume knob to adjust the volume of the GR-20 sound, and use the guitar's volume control to adjust the regular guitar sound.
(2006/01/20)