Yeah, it doesn't quite make sense, but what else could it be?? This is about as bare a circuit as one would find.
Are you in the USA?? I'd be happy to mail that capsule to you for further inspection.
-Scott
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On 6/25/24 13:08, sergio_logic via groups.io wrote:
The reason I am puzzled by the 33k on the DPA is not the value, but where it's connected.
Summarized by Sanken here <>, there are two topologies for the JFET
1. common drain AKA source follower AKA "3 wire method" (Shure uses this)
2. 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 presents <>this solution for use with Sennheiser bodypacks. As long as it's just a JFET with reasonably low Idss, either way works.
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---- Scott Helmke ---- scott@... ---- (734) 604-9340 ----
"I have ceased distinguishing between the religious and the secular,
for everything is holy" - Joe Henry
