The thing with the 9V battery in Pearl1 schematics ?

[citationfan]

Hi there,
Iam a proud owner of a secondhand Pearl one.
When looking through the schematics of it there is an option
to install a 9V battery between PAD 4 and 5, paralell to the diode 1N4739.
What is the backround?

 

[JonSnell Electronic]

All that will do is put a 9volt source across the zener diode, (it already has one through R5). Nothing else.

 

[6L6]

It was intended to be used as a voltage reference in lieu of the zener.

 

[citationfan]

Thank you very much guys for your answers!
Now my Pearl dead shot 2SK389(Q6) on each channel...