Threshold 4000 "polarity"
 

(sorry for my english)
I have two simply questions:
1) Was it inverting or not-inverting? (I haven't owner's manual)
2) I think it's time to replace the four original big capacitors: what is the minimum possible value for each ? ( numbers are illegible)
Thanks advanced for your time

P.S.: after 25 years( or more?) the amp is "perfect".

All the Threshold and Pass Labs amps/preamps are non-inverting.

Try 15,000 uF minimum at 75 volts. The big thing is to fit the
can in the same diameter bracket with similar height.

Thank you very much, Mr. Pass .
You are really "the one and only"!! :)
best regards from Venezia