U87 circuit, and HF roll-off curve

[LevinGuitar]

@LevinGuitar you were absolutely right, i replaced C110 and C107 with fresh ones, and bingo ! C105 is now back at 270pf, i increased C106 to 170nf and tried 8pf silver mika between drain and gate, i am now much more pleased by the sound, much better low end and the overall harshness nearly disapeared. Thanks to everyone here

You mean C104? 47nf to 170nf?

What you used for C110? MKT/polyester?

Can you share with us the current capacitance and resistance of your old C107 and C110? What year was built your mic approx?

 

[garp]

yes sorry C104 at 170nf C110 is now wima MKT. I can't mesure the old caps sorry next time i'll upgrade my multimeter to a modern one ! The mic is not very old probably around 2010 but was mistreated, i mean a lot

 

[AdamFrisen]

Also there is a series of VDO's here with the actual guy who designed a lot of the RODE microphones and he explains quite well his rationale and his decision making process.
I own a few RODE mic and find them very well built, fairly priced and of really good value.

He starts at the bases, but he gets in the actual innards in a very well presented fashion.
A must watch for all DIYer that want to further his knowledge.

This was interesting, using valve (tube) and getting those numbers.

20 minutes in the video:






and about the power supply: