how to mod a U87AI??????????

[vladi]

Hi, i have an U87AI and would like to remove the filter network on the microphone.
I want it be more open (more treble) ,the mike its dull if you compare it to the older ones
WHAT TO DO ????
here is the schematics

http://www.omnipressor.com/MicSchLib/u87ai.gif

TNX VLADI

 

[Gus]

Its easy but would not do it it might hurt your ears.

Modding a u87 is kind of funy to me. A u87 does what it does well.

How is it dull? It might be that the capsule needs cleaning or something is not right inside. Check the connections

 

[solder_city]

one question mark would have got the point across.

 

[ruairioflaherty]

Hi Vladi,

I would say that if you U87 is dull either it's faulty or your mic pre is faulty. The 87 is not a dull mic and many people dislike it for its "spitty" top - I on the otherhand like it a lot. Do a search on Klaus Heyne's mic forum where he talks about the KK87 capsule without filtering and feedback. IIRC it was up 6 or 8db in the higher frequencies - not nice at all.

Try and compare your 87 to someone elses to see if it is working properly or not. If not send her for repair.

cheers,
Ruairi

 

[vladi]

ts easy but would not do it it might hurt your ears.

Modding a u87 is kind of funy to me. A u87 does what it does well.

How is it dull? It might be that the capsule needs cleaning or something is not right inside. Check the connections

dont forget that i´m talking about the AI version the old one´s are really nice.

and i have 2 u87AI they sound the same.



Vladi

 

[Gus]

c106

Looks like disconnecting one end takes the network out, a better way might be to change some values, I need to think about this to figure out how the network works with the capsule and inverted signal from the drain


Another difference between the old and new is the capsule voltage.

That link has a added extra, someone measured the DC to DC converter coil.

 

[vladi]

tnx for your efforts Gus

any other suggestions ??

disconnecting c106 will disconnec the hp filter

 

[vladi]

I found this on the Klaus Heynen forum:

High amount of negative feedback, both, for overall gain and for eq, severe roll-off in the bass, 4dB down at 16k, and so on, all attribute to the (in)famous "honk" of the mic when the same capsule used in the much gentler processing of the SM69 and M269 tube models sounds so musical and engaging.

http://recforums.prosoundweb.com/index.php/m/3694/0/?srch=sex#msg_3694

 

[pstamler]

On a pair of the original U-87s I replaced the coupling capacitor from the FET to the transformer (originally tantalum) with a 1uF polycarbonate stacked-film. The difference was not subtle; it was like a compressor was taken off the mic. Oh, I also bypassed the Ta cap on the FET's source resistor with a 0.1uF film cap.

Peace,
Paul

 

[Gus]

Paul

Yes that can make a big difference but sometimes people like that tant sound. A good Al at c107 is fun to.