Hello,
I want to design a proper microphone preamp for the Monacor MCE-404U cardioid capsule, it seems it has a good price and performance.
http://www.monacor.co.uk/products/prosound-microphonecartridge/vnr/233690/?type=257&no_cache=1
To increase dynamic range and sensitivity, I want to bias the capsule at 9V with a 10k resistor. I thought in this configuration, the output impedance will be around 10k, thus requiring a high input impedance preamp. In this case, the noise current of the preamp should be minimised.
Looking at the datasheet, it seems the output impedance is only 680 Ohm, near to the impedance of a dynamic microphone, it doesn't need a high impedance and low current noise preamp. So the voltage noise of the preamp should be minimised.
I'm curious if this capsule, having a 0.5 mA DC current, is biased like all electret capsules, and if biased at 9V, with a 10k resistor, the output impedance will still be 680 Ohm.
I want to design a proper microphone preamp for the Monacor MCE-404U cardioid capsule, it seems it has a good price and performance.
http://www.monacor.co.uk/products/prosound-microphonecartridge/vnr/233690/?type=257&no_cache=1
To increase dynamic range and sensitivity, I want to bias the capsule at 9V with a 10k resistor. I thought in this configuration, the output impedance will be around 10k, thus requiring a high input impedance preamp. In this case, the noise current of the preamp should be minimised.
Looking at the datasheet, it seems the output impedance is only 680 Ohm, near to the impedance of a dynamic microphone, it doesn't need a high impedance and low current noise preamp. So the voltage noise of the preamp should be minimised.
I'm curious if this capsule, having a 0.5 mA DC current, is biased like all electret capsules, and if biased at 9V, with a 10k resistor, the output impedance will still be 680 Ohm.
I'll 2nd that! Even a guitar lowest E is 82Hz! You may not even hear the A string at 110Hz! You may still be able to buy a few, now obsolete Panasonic WM61A (20Hz-20KHz), perhaps little more expensive. Another alternative could be ;
Electret Microphone - 20Hz-20KHz Omnidirectional ID: 1064 - $0.95 : Adafruit Industries, Unique & fun DIY electronics and kits
Banzai Musikk.de may still have the WM61A?
These 2 caps would enable you to drive them in source follower mode = much less noise & more out put!
Electret Microphone - 20Hz-20KHz Omnidirectional ID: 1064 - $0.95 : Adafruit Industries, Unique & fun DIY electronics and kits
Banzai Musikk.de may still have the WM61A?
These 2 caps would enable you to drive them in source follower mode = much less noise & more out put!
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Naturally it is easier to make an omni-directional cartridge with a more extended low frequency response, since an omni is a sealed cartridge and is sensitive to pressure variations. Notice the vent holes on the back of the cardioid cartridge the OP posted? This makes the cartridge insensitive to pressure variations and gives the cardioid response, it's so small though that low frequency response suffers in this case.
What we need to know is which is more important, the polar pattern or the frequency response? For a measurement mic the omni is correct, but perhaps not here. Another alternative is to combine to omni cartridges to make a pseudo cardioid one (I'll find the link later)
What we need to know is which is more important, the polar pattern or the frequency response? For a measurement mic the omni is correct, but perhaps not here. Another alternative is to combine to omni cartridges to make a pseudo cardioid one (I'll find the link later)
Thank you for the responses.
I want to use a cardioid capsule, because I want a significant attenuation of the room background noise; it will be used only for speech, not for singing or musical instrument recording.
The MCE 4000 omni capsule is also available here, but I would prefer a cardioid capsule, and the MCE 404 is the only type available. As I see, small cardio capsules are rare to find in general, at least here many shops only sell complete microphones.
Regardind the WM61A capsule I see it is very good for measurement but it was unfortunately discontinued. You say with the source follower/Linkwitz mod it provides more output and less noise? I thought the source follower mod reduces distortion with high SPL sounds, and also reduces the gain, this gain reduction being compensated in the preamp.
I built a preamp using the LM833 opamp, which has an optimum source impedance around 9 kOhm. Probably the noise will be mostly determined by the internal JFET in the capsule anyway, and the preamp noise is not significant.
A Happy New Year to everyone!
I want to use a cardioid capsule, because I want a significant attenuation of the room background noise; it will be used only for speech, not for singing or musical instrument recording.
The MCE 4000 omni capsule is also available here, but I would prefer a cardioid capsule, and the MCE 404 is the only type available. As I see, small cardio capsules are rare to find in general, at least here many shops only sell complete microphones.
Regardind the WM61A capsule I see it is very good for measurement but it was unfortunately discontinued. You say with the source follower/Linkwitz mod it provides more output and less noise? I thought the source follower mod reduces distortion with high SPL sounds, and also reduces the gain, this gain reduction being compensated in the preamp.
I built a preamp using the LM833 opamp, which has an optimum source impedance around 9 kOhm. Probably the noise will be mostly determined by the internal JFET in the capsule anyway, and the preamp noise is not significant.
A Happy New Year to everyone!
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