because maxon od-820 has internal voltage 9v? ICL7660

[ANDYEFFECT]

does maxon od-820 voltage intern 9v? 
 
I opened my pedal and I measured some voltages, pin 8 9volt. 
 
Is ICL7660 just placed in the circuit to maintain voltage? 
 
I thought that they will use to increase for 18v. 
 
Which the advantage in the circuit with ICL7660? 

thanks.

[JHS]

The OD-820 has internal +/-9V (18V swing) supply and a better filtering of the generated voltage. The MAX-1044 circuit layout in the 820 is better than that shown in the MAX-datasheet.

The MAX-1044 can deliver 10mA of continious current (boost closed) w/o any problems thats enough for the 820 with the two JRC 4558.
If you want to swap the ICs to TL072 or OPAs you should use another charge pump which can deliver 20mA or more.

JHS