KM54c SDC Tube Mic Build / Gefell mv691 Mod

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HarmonyUnited

Well-known member
Joined
Jun 21, 2016
Messages
63
Location
Santa Cruz, CA
Yah, the mic sounds amazing. I love it...

The process with the dropping resistor is simple. You will see two holes near the center pole of the capsule housing. Mine were filled with silver wax which you don’t really need... I saved it and pushed it back in after. Those are the holes you need to use to spin that plate that will unscrew the housing to remove the grill. The resistor is not in series with capsule but rather a shunt in parallel... you can either just clip it out if you don’t want to deal with desoldering near capsule. But Id recommend just covering the capsule part with a small clean plastic  bag (I had tons from mouser) and using a soldering iron to just melt the solder on the resistor and pulling it out of the circuit.... just be mindful and aware to not get any solder on the capsule. I found the process to be really easy and simple...

Good luck , let me know if you have more questions! :)

Eric
 

vitopower

Well-known member
Joined
Jul 23, 2009
Messages
112
Location
St. Louis, MO
I'm trying to setup this build but I understand the voltages are intended to be electrostatically measured and I only have cheap digital multimeters.  I can see b+ appear to jump from about 123v before settling a few seconds later at 120, but I'm afraid that it might be jumping from a higher number than the meter has time to respond to.

Is there a way to get around this aside from buying an electrostatic meter, or VTM or building a null detector  :eek: ?  My DMM is adding 1M in parallel, so I could increase that total resistance by orders of magnitude, I think, which decreases the loading effect but the meter will be closer to its error range at lower settings.
 

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