I recently got my hands on some 6mm electret from a China seller that has below listed specs:
Sensitivity: 52dB
Impedance: 2.2 KΩ-30%
Flat rate: 20 ~ 16.000HZ
Operating voltage: 10V (TVU)
Reference operating voltage: 4.5V
Current consumption: 0.5mA (max)
Sensitivity attenuation: ≤-3dB at 2-1.5v
Now as far as I understood electrets, most of them should have a built in FET that will already charge & polarize their diaphragm and will work as long as you supply power to the right leg. However my test with the below circuit (and another simple condenser circuit, both circuit works with the default electret that came in the cheap BM800 mic) yielded nothing no matter which leg I connect to, so either I'm misunderstanding something, or this is actually a non-polarized capsule that requires an external FET to work: (If this SDC could work, I plan to put some of them into a Simple P48 circuit.)
(This is the XJM0013A electret ciruit, and my frequency measurement matches with the findings in this blog - A Few More China Mic PCBs Measured, also measured an output voltage of 7.7+, so the zener diode is possibly a 9v - measured direct probing @ 8.8V)
So as I've a few more experiment/test to play with, I hav some questions regarding them below:
1. How do you identify electrets which need external FET(or not for the matter, the electret model no. here is CWFBI0350 / 7D0266B)?
2. On a side note, I plan to modify the XJM electret circuit shown above (by changing the zener to possibly a 11V or 10V to increase the operating voltage closer to 10V for most electret capsules), will this also increase the noise floor alongside the sensitivity?
3. In electret circuits like these, if I liked to clean up the signal by adding additional HPF stage, should I implement it before or after the FET (Can the same be applied the same way and be as effective in a simple P48 circuit?)
(Mic Circuits From Simple to Professional Source pic taken from here too)
4. Also regarding the simple circuit found above in some of the cheap BM800 mics, since they are unbalanced, is it possible to make them a pseudo-balanced circuit by adding something like a RF filter like described in this (Mic Circuits From Simple to Professional) from pin1 to pin 3 of the xlr?
Thanks a bunch in advance, and thank you for your patience & attention.
P.S before anyone asks, I'm having various sized electret capsules (9mm, 16mm, 25/26mm) coming soon, I'm planning to make a male XLR mount for them so that I can combine the electret circuit easily withn anyone of them once I mount the PCB into a pencil sized shell)
Sensitivity: 52dB
Impedance: 2.2 KΩ-30%
Flat rate: 20 ~ 16.000HZ
Operating voltage: 10V (TVU)
Reference operating voltage: 4.5V
Current consumption: 0.5mA (max)
Sensitivity attenuation: ≤-3dB at 2-1.5v
Now as far as I understood electrets, most of them should have a built in FET that will already charge & polarize their diaphragm and will work as long as you supply power to the right leg. However my test with the below circuit (and another simple condenser circuit, both circuit works with the default electret that came in the cheap BM800 mic) yielded nothing no matter which leg I connect to, so either I'm misunderstanding something, or this is actually a non-polarized capsule that requires an external FET to work: (If this SDC could work, I plan to put some of them into a Simple P48 circuit.)
(This is the XJM0013A electret ciruit, and my frequency measurement matches with the findings in this blog - A Few More China Mic PCBs Measured, also measured an output voltage of 7.7+, so the zener diode is possibly a 9v - measured direct probing @ 8.8V)
So as I've a few more experiment/test to play with, I hav some questions regarding them below:
1. How do you identify electrets which need external FET(or not for the matter, the electret model no. here is CWFBI0350 / 7D0266B)?
2. On a side note, I plan to modify the XJM electret circuit shown above (by changing the zener to possibly a 11V or 10V to increase the operating voltage closer to 10V for most electret capsules), will this also increase the noise floor alongside the sensitivity?
3. In electret circuits like these, if I liked to clean up the signal by adding additional HPF stage, should I implement it before or after the FET (Can the same be applied the same way and be as effective in a simple P48 circuit?)
(Mic Circuits From Simple to Professional Source pic taken from here too)
4. Also regarding the simple circuit found above in some of the cheap BM800 mics, since they are unbalanced, is it possible to make them a pseudo-balanced circuit by adding something like a RF filter like described in this (Mic Circuits From Simple to Professional) from pin1 to pin 3 of the xlr?
Thanks a bunch in advance, and thank you for your patience & attention.
P.S before anyone asks, I'm having various sized electret capsules (9mm, 16mm, 25/26mm) coming soon, I'm planning to make a male XLR mount for them so that I can combine the electret circuit easily withn anyone of them once I mount the PCB into a pencil sized shell)
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