Felipe,
You can wire up a power LED for the GK1 from the positive power supply of say the left channel SS section.
This is at +14.4 volts +0.6, -1.
If we assume 14.4V and a LED voltage of 2, and gun for say 3mA, then the dropper resistor from the positive supply to the anode of the LED will be (14.4 - 2)/0.003 = 4133R. Nearest preferred value would be 3K9, giving a current of 3.18mA, near enough for government work.....
The kathod of the LED would be directly connected to preamp earth.
Hope this helps,
Cheers,
Hugh
