Piezo preamp rebuild

My Stagg double bass has a noisy preamp that precludes recording it. I should replace it. One day.

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This is a "placeholder" project to remind me that I should, among other things, design a proper, ultra-low-noise preamp to replace the lousy circuit installed in this bass. Since my 20S, I'm used to replace the electronics of my 4-stringers but this one is piezo and I should investigate more instead of putting a '741 in voltage follower configuration...

1. A discrete op-amp ?

  • A discrete op-amp ?

    Yann Guidon / YGDES05/02/2016 at 00:34 0 comments

    Coincidences are great.

    I need to make a preamp (voltage follower, mostly) for this bass. Impedance must be low but noise must be minimal.

    OTOH in another project, I am considering building a discrete amplifier.

    I could use an integrated circuit but I'm not sure that would answer all the questions that might appear. But since low-noise, low-power signal amplification is a goal shared with another project, it is possible to share insight and designs.

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AVR wrote 05/21/2016 at 19:20 point

Following cause I wanna do custom guitar piezo electronics, eh and MIDI digitizing :)

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Vito wrote 05/02/2016 at 09:01 point

You don't need to make an entire op-amp for that: I suggest you a J-Fet preamp and careful shielding:

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Yann Guidon / YGDES wrote 05/02/2016 at 14:58 point

Hello Vito,

Indeed I'm looking at discrete JFET amplification for the #Active scope probe with no dedicated power supply. While looking at differential amplifiers on google, I found a lot of audio circuits as well, including this one

I don't remember where I found it but with some enhancements (offset trimming, current sources instead of certain resistors) it makes a semi-decent op-amp that I can set to unity gain. That got my headgears spinning...

I won't try to reinvent something revolutionary, just remove the noise that keeps me from using my instruments for recording. I know that audio amplification is one of the golden applications of electronics and everything has been tried already :-D

If you have other F-FET suggestions, thank you for sending more links, I'll study them !

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