Flatpicker said:
Replace C1 with a 1000pf polystyrene (just like on the other mic). Replace C7 (? can’t read the value) with a Panasonic miniature metallized film “V” series of the same or larger value (whatever fits). Replace C9 with a Panasonic “FC” series electrolytic cap.
I would also suggest trying polypropilene caps, which to my ears sound better. It seems that this is a LDC mic, so you might have much more room to fit it here. C7 works in parallel with C?, (which is in series with S4 switch), so replace C7 with the same value, to get bass cut, and C? with the highest value of polypropilene cap you can fit. Also, instead of C9 I would recommend polypropilene, as well, as it tends to sound better than any, even highest quality electrolitics, including Black Gates. 2-3Mf caps instead of C? and C9 would be more than sufficient.
As Crazydoc has already noticed, the trafo here would be the main objection though, and should be replaced with high quality Lundahl, or at least re-lamed with good quality Nickel core. Otherwise, you probably won't hear much difference with caps replacement.
Please notice, this mic uses a RC network around primary of the trafo on R11 and C10. This is a well known trick from old good days of tube amplifiers, and tends to increase performance of not very good trafos. If you decide to replace/relam it, try to disconnect this network and see which way you like better.
