Not that capacitance directly in parallel with a zener has limited effectiveness to begin with, but yeah - RC filtering downstream is to be desired.
Warm Audio WA-84
- Thread starter Emmathom
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Not that capacitance directly in parallel with a zener has limited effectiveness to begin with, but yeah - RC filtering downstream is to be desired.
Cqwet Dbdfte
Well-known member
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- Oct 2, 2023
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yep, the capacitance with the Zener impedance would be the first RC time constant, but better add some more R before the C.
Hi folks
Thanks for your comments and advice. In the end I will not change the components because I don't think that the problem comes from there.
Already, in the past, I had to clean the circuits 3-4 times with IPA and the mic worked again... 'till next failure.
I think, as some of you pointed out, that the problem is at the level of the very high impedance of the capsule : the 1Go, the 470nF and the gate of the fet. This circuit is very poorly implemented in my opinion. When i build my own circuits I always make sure that the capsule coupling cap (if present), the gate leakage R and the jfet gate are connected together as close as possible and "in the air" without touching the PCB. in the WA84, the jfet is away from the capsule (2cm = quite far) and the connexion is made thru the PCB which is coated with a "resin" that melts with the solder.
The other mic works but I think it's about "luck". I'm sure to be able to build a much better circuitry than this crappy thing...
I don't want to modify the circuit knowing that I want to resell these microphones. I would do it if I wanted to keep them by redoing the PCBs on verobaord...
So I will clean the head, test continuity between capsule's peak and jfet gate, then clean again and again...
Thanks for your comments and advice. In the end I will not change the components because I don't think that the problem comes from there.
Already, in the past, I had to clean the circuits 3-4 times with IPA and the mic worked again... 'till next failure.
I think, as some of you pointed out, that the problem is at the level of the very high impedance of the capsule : the 1Go, the 470nF and the gate of the fet. This circuit is very poorly implemented in my opinion. When i build my own circuits I always make sure that the capsule coupling cap (if present), the gate leakage R and the jfet gate are connected together as close as possible and "in the air" without touching the PCB. in the WA84, the jfet is away from the capsule (2cm = quite far) and the connexion is made thru the PCB which is coated with a "resin" that melts with the solder.
The other mic works but I think it's about "luck". I'm sure to be able to build a much better circuitry than this crappy thing...
I don't want to modify the circuit knowing that I want to resell these microphones. I would do it if I wanted to keep them by redoing the PCBs on verobaord...
So I will clean the head, test continuity between capsule's peak and jfet gate, then clean again and again...
