boylesg
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You should do that.will have to scan the printed schematic that came with the kit.
But the printed documentation says that you can use an electret microphone with it.An electret mic has a Jfet inside as an impedance converter. The Jfet must be powered with a bias current of about 0.5mA with a few DC volts that the preamp does not provide.
This simple preamp is made for a dynamic mic (coil and magnet like a tiny speaker) that generates a signal.
You should do that.
The kit description says "Signal Input Level 52mV", not actually microphone sensitivity.
- - - Updated - - -
O.K., pre-amp sensitivity 2 - 5 mV, should work.
You have two microphones that do not work then probably there is something wrong with the kit amplifier.
Hello boylesg,
The Kit: KC5519 is not featured in Short Circuits 3, unless they did a revamp of that projects magazine.
The kit you're referring to is an updated version of the early champ and pre-champ amplifiers.
Silicon Chip magazine designed the updated version with different audio IC's (much better quality ones),
and basically gave it a much improved sound output.
I've checked the notes and errata on all projects of 2013 and there are no mistakes with the original design.
You don't need to use two microphones on this project, as the two pre-amplifier op-amps will end up being
summed together anyway, so you won't get stereo out, as the project was designed for mono operation.
To install an electret mic, please see the picture below:
Electret
With all the electret microphones I've used are normally polarity conscious, so make sure you insert it the
right way around.
You can usually tell by one of the pins being attached to the body of the mic via a small track.
Please let us know how you get on.
Regards,
Relayer
The output capacitor value on the preamp is crazy at 470uF!! Calculate how long it needs to charge. It will be fully charged 110 seconds after the circuit is powered when the amplifier begins playing properly.
For a low frequency cutoff at 34Hz then the capacitor is calculated to be 4700 times less at 0.1uF when it will be fully charged in 0.024 of a second.
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