C1 and C2 are there for RF suppression.The value of 22 nF may be at bit high, and cause HF rolloff.But I would never remove them completely.Substitute them with a lower value.1 to 4,7 nF will still give you RF suppression, without noticable HF rolloff.(The output impedance of the PNP transistors in series with the 20 ohms resistors is low.)OR:Remove the capacitors en replace the 20 ohms resistors with 47 uH mini inductors.
Wouldn't a slight HF roll-off be a good thing to keep, given the K67-style capsule?
I turned this thing into a u87. Check Poctop's u87 thread I added documentation specific to this version of the B2, if you decide to go that route.
Oh, unless it happened today, it helps to add a post #. Long thread.
All of these caps also affect phase.All four are not needed. In case of hf damping as also RF 10nF between FET and first BJT to ground.Many microphones don't have RF filtration at all and they works. If owner had no problem with RF after removing caps then why should it be used? Ruud, this isn't typical schoeps topology, similar somehow but there is no PNP pair at the output.It's combination PNP/NPN.I also don't recommend to use caps before them
Everything is correct, but wait with order, there will be few things more. I'll let you know later.
Ok, here's a full list of parts:2x 1nF Wima FKP (small size min.100V rated)1x 4.7nF can be wima fkp or mkp (small size)1x10nF can be wima fkp or mkp (small size)4x 68uF/63V electrolytic caps (panasonic FC or FM, BC components etc.)10x 2n5087 10x2n5088 (from the same manufacturer as 2n5087)4x470nF/63V capacitors (wima, ero, anything which would fit PCB - fkp, mkp, mkt, mks), best 5% tolerance1x7.5V Zener (0.5W-1W)I assume that your multimeters have options for HFE and capacitance mesurements?