I'm wiring an external piezo as contact mic to the TRRS 3.5 jack of a MacBook Air. I'm following the instructions on this post: Piezo contact mic into iMac - avoid signal spikes

However, the answer to this question is not clear, and the provided link in the answer to this question is now dead.

Where in the circuit should I add the two LEDs to prevent signal spikes? Piezo circuit diagram

I am new to wiring microphones, so please let me know if I am omitting any information that you need to answer this question!


1 Answer 1


The two LED's should be connected in anti-parallell like this, in order to limit the voltage from the piezo. Schematic with LED's added

By the way, you can often open dead links with Wayback Machine.

  • \$\begingroup\$ Thanks for the information, this is really helpful! \$\endgroup\$
    – Joji
    Feb 5, 2022 at 10:44

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