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Fet preamp circuits for dynamic microphones

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computerlen:
I would like to converse with others on this topic. Presently I am making microphone preamps or boosters [like the cloud lifter and fet head] for low output dynamic microphones such as the Shure SM7 and ribbon mics that operate on the 40 volt phantom power of audio mixers. These preamp circuits work perfectly but I have questions about why does this happen and why does that happen? You might disagree with me but I have found that blue leds operate on the 25-40 volt phantom supplies with 5meg and more resistors in series with the leds. I have even wired 4 blue leds in series with the 2.2MEG OR 5 meg resistors in series with them connected to the phantom voltage on pins 2&3 of the male XLR CONNECTORS. THANKS. LEN. [you are welcome to get in touch with me at computerlen@hotmail.com. This might be faster]

Zero999:
A phantom power supply is used for a condenser microphone, not dynamic.

Why do you want to use a FET input amplifier for a dynamic amplifier? Dynamic microphones have a low impedance, so a high input impedance FET input amplifier is not necessary and will have a higher voltage noise, than a BJT input amplifier, everything else being equal.

Bassman59:

--- Quote from: computerlen on August 01, 2020, 09:50:44 pm ---I would like to converse with others on this topic. Presently I am making microphone preamps or boosters [like the cloud lifter and fet head] for low output dynamic microphones such as the Shure SM7 and ribbon mics that operate on the 40 volt phantom power of audio mixers. These preamp circuits work perfectly but I have questions about why does this happen and why does that happen? You might disagree with me but I have found that blue leds operate on the 25-40 volt phantom supplies with 5meg and more resistors in series with the leds. I have even wired 4 blue leds in series with the 2.2MEG OR 5 meg resistors in series with them connected to the phantom voltage on pins 2&3 of the male XLR CONNECTORS. THANKS. LEN. [you are welcome to get in touch with me at computerlen@hotmail.com. This might be faster]

--- End quote ---

What is your question, exactly?

Whales:
Indeed, I don't understand what you're asking.

You start with something about pre-amps, but then talk about your surprise that LEDs can be powered by the phantom power supply used for mics?  Phantom power is normal electricity, no ghosts involved.

Perhaps you're asking for designs of phantom-powered pre-amps?

magic:
Not sure if OP is a robot or just needs to sober up after Saturday :-//

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