Actually not that easy to do. I also adjust the values for the capsules And I test the mics for distortion before and after the mod and adjust values based on each capsule / and expected operating voltage to maximize output and minimize distortion.
And Even I cant get the mod to be reliable inside a 3.5 mm plug and I am the one that came up with it. Thats why I only do that mod to the capsule. Unless its a countryman mic where that is impossible.
There's an electronic shop not very far to me . But what should I ask them exactly ? I mean if they never made this I have to be very accurate in the description of what they have to make ! and except the diagram I have not lots of informations, how do you check all this values then ? when you tell you test the mics for distortion before and after , etc ... can they do that too ?
I would go ahead and give them the schematics, ask them to do it, and then test the mics in a non-critical situation afterwards. Find a local band at a bar or club to tape, or just crank up your stereo and stick the mics right next to the speakers. If it sounds OK, then things should be fine. What Chris does is awesome, he goes the extra step to make sure the mics are balanced and performing well with extensive testing, but if the mod is done well by someone else, with the proper resistors, then that testing isn't needed. I had my B3s modded by someone without the testing equipment, and it worked out great. PM tgakidis or darktrain, ask them which connector and resistors they use, and have that information ready when you go to the shop. It's really not a huge deal and should only cost you 20-30 Euros or so.