Web Audio API: Pan audio (left/right) + controlling gain

I want to create a very basic AudioContext()-instance playing a sound either on the left or on the right channel.

I know, there is already an answer about this here: http://ift.tt/1zCOPkX

My problem is, I have to control the gain via a GainNode.

Whenever I conntect the GainNode, it makes the left/right channel to output sound again.

I extended the original Example from the answer with a GainNode: http://ift.tt/1zCORZT