How long do NOS 6L6gc power tubes last in a Mcintosh MC240 amp?

>> greatest improvement you can make is to add a film cap to the 100uf electrolytic cap in the feedback circuit.

Just finished restoring my MC240 and noticed the above comment from 2020. Can you give a couple more details?

-- What value of film cap, and how wired?

-- What's the goal here?

Thanks!

Phil Nelson (philsoldradios)

https://antiqueradio.org/index.html

Phil - the smaller cap in film sounds better than the single larger cap alone. Like all things audio, some hear it, some don't… The rule of thumb is 10% of the larger cap, use same voltage rating !  My 240 is singing for her supper ;-) 

A long time