How do I discharge the capacitors in my PS audio P20 ?

Assuming you don't have a 10watt 1k resistor on hand, you could use a 40w light bulb.

@hiendmmoe

I am interested in this as well.  This link seems to give a good explanation. 

https://www.nextpcb.com/blog/how-to-discharge-a-capacitor-comprehensive-guide

The nextpcb article above says to short caps with a screwdriver. I do not recommend subjecting power capacitors, especially electrolytic ones to a dead short as they may be permanently damaged.

It's possible that the PS Audio unit already discharges the caps on power down. Measure with DMM set to Vdc and relevant range. 

You culd also just unplug it and wait 24 hours

Ask PS Audio