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Post subject: Why this guitar piezo opamp buffer lacks any sort of bass
Posted: Thu Jan 12, 2017 12:01 am
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My preamp in my acoustic guitar died after I put the battery in backwards. I need to replace it, and fast. Piezos have incredibly high output impedance (5+ mohm) so a buffer circuit is used to knock the impedance down to a sane level.

I tried building this circuit and while it works, it lacks any sort of bass amplification:Image
I didnt have a 100k resistor, so r3 is 170k. I also didnt have a .1uf, so c1 is 4.7uf. I tried raising the r2 to 5mohm and it sounded the same. v+ is 9v and vb+ is 4.5v from a voltage divider. OpAmp is tl072

All caps are thin film, not electrolytic

The DI Box next in the chain has an input impedance of 1mohm
Any help or alteratives much appreciated!


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Post subject: Re: Why this guitar piezo opamp buffer lacks any sort of bas
Posted: Thu Jan 12, 2017 2:26 am
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Joined: Fri Feb 05, 2010 4:31 am
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Location: Province de Québec, Canada
Put the right values first. It may fix the bass.

Schematic show a 'lytic cap at C2 and you write you did not use electrolytic !!!


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