Converting a D-87 to ORS87

[joulupukki]

I've got a D-87 (Dany Bouchard) that I've built into an Aurycle A460 mic body. I originally had it built using an Arienne Audio K87 capsule but I've since swapped it out for a JLI TSC-2 capsule (because I used the Arienne for my Fuchs U87a). With both cases I've been underwhelmed by the lack of sensitivity of the D-87 and would like to change it if possible so it's closer to what the Fuchs U87a would be (and my other condenser mics).

As is, the -10dB pad and low cut filter switches are functional.

I'm currently using a 33V Zener with a 47K at R17.

It's been suggested that the ORS87 would yield better sensitivity so I wouldn't have to turn up my preamp so high. I'm starting this thread so I don't pollute the D87 build thread anymore. Has anyone else done this conversion with satisfying results? As pointed out by @micolas I think it's just going to be a matter of tracing both circuits and removing what no longer belongs on my existing circuit board. Right?

 

[Khron]

You've been warned you'd be giving up the omni & fig-8 patterns, right?

 

[joulupukki]

You've been warned you'd be giving up the omni & fig-8 patterns, right?

When I switched from the AA K87 to the JLI TSC-2 I already gave up one of those. I've never used omni or fig-8 with this mic anyway. I've got a modded AKG P420 and the Fuchs U87a for that purpose if needed.

These are the U87 schematics I've been referencing with the D-87 build:

http://recordinghacks.com/images/mic_extras/neumann/U87-schematic-1972.png
http://recordinghacks.com/images/mic_extras/neumann/U87-schematic.png

 

[joulupukki]

If I’m looking at the ORS87 schematic right, I think if I were to make the following changes, that’d change it to where it’d be in the right territory. Right?

Is the main reason for the increase in sensitivity the fact that C4/470pF is removed in the ORS87?

 

[Khron]

I think if I were to make the following changes, that’d change it to where it’d be in the right territory. Right

If you replaced C1 with a jumper, you'd hard-wire the mic to omni.

C4 can indeed be bypassed; might just be simpler to just move the capsule wire from the turret where C4/R6 were joined, to where R7 & the JFET gate are joined.