
Looking at the schematics, I think that leaving Pin 3 floating is best.
Shorting to GND will load the output OpAmp unduly, generate a lot of heat and create extra distortion.
The manual states that the output stage wants to see a load greater than 600 Ohms.
I am using the dual RCA output with short interconnects to BiAmp my speakers.
Hope this will help anybody who wants tripple outputs from the BP20/25 or 26 in future.
Cheers