tynkerd
Member
- Joined
- Oct 17, 2018
- Messages
- 5
Hi guys, I'm new on the forums here, and I'm just getting started with mics as a hobby.
I bought a cheap Chinese condenser capsule (appearance is similar to the RK-87 by micparts), and am trying to figure out how to read the output voltage, to make sure the thing even outputs a signal voltage.
Basically, I know these are high-impedance, so they can't deliver much current. Because of this, I can't directly hook up power and use my oscilloscope to measure AC signal variations, because the 1M ~ 10M ohm load draws too much current.
So, I've made a super-simple circuit (attached), with:
-1G-ohm resistor connecting the capsule and +40V
-100nF capacitor to separate only the AC signal
-1G-ohm resistor to pull the bias of the JFET to 0V
-JFET has a 10k-ohm resistor to +40V at the drain (the JFET draws ~3-4mA @Vgs = 0V)
-Vdrain sits at around 2.xxx[V]
I was expecting to see a signal when I clap or shout or do something, but I don't notice ANY changes.
All my oscilloscope shows is this 50Hz jibberish, probably from the power supply or something...
Any hints on how to measure a mic capsule to see if it is even outputting signal changes when sound pressure waves pass through, would be hugely appreciated! Thank you so much!
I look forward to jumping into the community here, and being a benefit once I get the basics out of the way.
I bought a cheap Chinese condenser capsule (appearance is similar to the RK-87 by micparts), and am trying to figure out how to read the output voltage, to make sure the thing even outputs a signal voltage.
Basically, I know these are high-impedance, so they can't deliver much current. Because of this, I can't directly hook up power and use my oscilloscope to measure AC signal variations, because the 1M ~ 10M ohm load draws too much current.
So, I've made a super-simple circuit (attached), with:
-1G-ohm resistor connecting the capsule and +40V
-100nF capacitor to separate only the AC signal
-1G-ohm resistor to pull the bias of the JFET to 0V
-JFET has a 10k-ohm resistor to +40V at the drain (the JFET draws ~3-4mA @Vgs = 0V)
-Vdrain sits at around 2.xxx[V]
I was expecting to see a signal when I clap or shout or do something, but I don't notice ANY changes.
All my oscilloscope shows is this 50Hz jibberish, probably from the power supply or something...
Any hints on how to measure a mic capsule to see if it is even outputting signal changes when sound pressure waves pass through, would be hugely appreciated! Thank you so much!
I look forward to jumping into the community here, and being a benefit once I get the basics out of the way.