The cap must be large enough to avoid peaking at max gain setting.
A point you must make sure when testing.
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If it had worked, the gain would only be x2, with somewhat higher distortion than normal.
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Your needs will be met with the single BC547 transistor 3 resistors two capacitors and electret capsule. " The first transistor amplifies the signal from the microphone so you can hear a pin drop" http://www.talkingelectronics.com/projects/14 FM Bugs/20 FM BUGS.pdf
A reference document.
Texas instruments publication on electret microphone and electret microphone preamplifier.
http://www.ti.com/lit/ug/tidu765/tidu765.pdf
Texas instruments publication on electret microphone and electret microphone preamplifier.
http://www.ti.com/lit/ug/tidu765/tidu765.pdf
I didn't expect this thread to resurrect from the dead. I agree with the assessment that this preamp isn't suitable for an electret capsule.
To address a few points:
The little soic4 diode bridge is much smaller physically than four 1n4001. How is it overkill ?
1meg-100nf for the servo is what is shown for the ina217 datasheet or the original that1510-1512 datasheet. In this board, the potential problem is that the servo cap is a 1206 cap. In that package, you can easily get a 100nf C0G cap but higher value smd caps with a decent dielectric aren't as common. Some smd 1206 film caps do exist and could be substituted, with values up to 1uf.
To address a few points:
1k2 is coming from this app from THAT: http://www.thatcorp.com/datashts/AES129_Designing_Mic_Preamps.pdf I've encountered such values in various pro gear.
The little soic4 diode bridge is much smaller physically than four 1n4001. How is it overkill ?
1meg-100nf for the servo is what is shown for the ina217 datasheet or the original that1510-1512 datasheet. In this board, the potential problem is that the servo cap is a 1206 cap. In that package, you can easily get a 100nf C0G cap but higher value smd caps with a decent dielectric aren't as common. Some smd 1206 film caps do exist and could be substituted, with values up to 1uf.
I realize that this thread is a few years old. This is my first time making a microphone pre-amp. I will follow up on @inkl's question above asking more specifically why I cannot use the SSM2019 pre-amplifier in conjunction with an electret condenser mic capsule. I have several of these capsules as well as several SSM2019 that are available for me to use, so if possible and not a terrible idea I would like to try them together. I will post this here, but possibly follow up with a more stand-alone question since this is piggybacking off of someone else's thread.
Some quick background:
Before the pandemic I purchased a bunch of AOM 5024L electret condenser mic capsules based on someone's recommendation, due to what seemed like a flat frequency response over a broad range, high sensitivity (-24dB) and a favorable reported signal to noise ratio of 80dB (see spec sheet). With careful soldering and otherwise very little modification to this mic capsule, I attempted to use it w/ a commodity USB-Audio Mic input (Tripp Lite) as well as with a consumer grade Amp (FocusRite). Unfortunately the amplitude of the signal recorded via the capsule on either of these devices was too faint to be useful.
This led me to think that I might need some sort of a pre-amplifier to amplify the measured potential before it reaches the above USB-Audio DAC. Currently I would like to revisit the use of these capsules, as it would be a shame to let them go to waste. In my brief research about microphone preamplifiers, I came upon the Analog Devices SSM2019 (where I saw it used by someone making an impedance tube).
Above I have posted a recommended drive circuit, showing that there is some internal circuitry inside the capsule. It could be that I was miswired this altogether and should try again, since I might be trying to listen across the wrong points in the circuit.
Thanks for any pointers and for clarifying about the issue of why a SSM2019 is not useful for this type of mic. First time working with this type of audio electronics.
`
Some quick background:
Before the pandemic I purchased a bunch of AOM 5024L electret condenser mic capsules based on someone's recommendation, due to what seemed like a flat frequency response over a broad range, high sensitivity (-24dB) and a favorable reported signal to noise ratio of 80dB (see spec sheet). With careful soldering and otherwise very little modification to this mic capsule, I attempted to use it w/ a commodity USB-Audio Mic input (Tripp Lite) as well as with a consumer grade Amp (FocusRite). Unfortunately the amplitude of the signal recorded via the capsule on either of these devices was too faint to be useful.
This led me to think that I might need some sort of a pre-amplifier to amplify the measured potential before it reaches the above USB-Audio DAC. Currently I would like to revisit the use of these capsules, as it would be a shame to let them go to waste. In my brief research about microphone preamplifiers, I came upon the Analog Devices SSM2019 (where I saw it used by someone making an impedance tube).
Above I have posted a recommended drive circuit, showing that there is some internal circuitry inside the capsule. It could be that I was miswired this altogether and should try again, since I might be trying to listen across the wrong points in the circuit.
Thanks for any pointers and for clarifying about the issue of why a SSM2019 is not useful for this type of mic. First time working with this type of audio electronics.
`
You should check out this article. Those capsules make excellent mics and don't need their own preamp provided the recording device you plug into can provide power: either 48V phantom power eg from a USB recording module, or low voltage 'plug-in power' from portable recorders etc. The article covers both scenarios.
https://www.instructables.com/The-Sound-Sleuthers/
https://www.instructables.com/The-Sound-Sleuthers/
When you say this do you mean that I might want to use a low noise LDO (such as ADM7154) on the 3V supplied by an 1/8" audio jack? It's true that the TrippLite USB-Audio DAC I'm using might contribute significant noise on it's own.
