The reason I am puzzled by the 33k on the DPA is not the value, but where it's connected.
Summarized by Sanken , there are two topologies for the JFET
- common drain AKA source follower AKA "3 wire method" (Shure uses this)
- common source AKA "2 wire method"
In both topologies, the resistor is connected at the node where the audio signal is coupled because it's the load resistor of the amplifier.
This is why it would be "abnormal" for the DPA, in a "2 wire" connection, to have a 33k resistor between source and ground while coupling the audio signal from the drain: Sanken shows a dead short there.
"Abnormal" assuming it's just a JFET, of course.
FWIW I've connected WL185s in the 2-wire topology (black wire to shield, red wire as bias and audio) to a TRS jack, and they work fine with consumer grade mic inputs (Rode Wireless GO, Zoom H1n, etc.). In fact, Shure this solution for use with Sennheiser bodypacks. As long as it's just a JFET with reasonably low Idss, either way works.
