Neumann W495stb output capacitor..

[Dubka]

Guys,
I'm just adding some output transformers to my W495stb and wondered what this capacitor is for.  And, depending on it's function, what's the best variety of capacitor to use for this purpose?
Cheers

 

[kooma]

zobel?

 

[Dubka]

Ah, so it's something to do with setting impedance?

I guess I'll try a poly…  ???