[PD] (OT) safely connect piezo transducer to soundcard as microphone

katja katjavetter at gmail.com
Sat Apr 21 00:42:42 CEST 2012


A piezo transducer often produces a signal level somewhere inbetween
mic level and line level (it depends on size, and method of
excitation). Indeed it can be too loud when mic input is used.

Another point of concern is impedance, which influences the sound
character. If you mount a resistor (in series), the signal level is
reduced but the sound is altered as well. Mounting a capacitor (in
parallel or series) also works to reduce signal level and alter the
sound. Combinations of these (RC networks, effectively) are a great
way to tune the sound character to your liking, but it takes a lot of
experimentation. Also, the result may be different for each (mic)
preamp because input impedance is not fully standardized.


On Sat, Apr 21, 2012 at 12:12 AM, Matteo Sisti Sette
<matteosistisette at gmail.com> wrote:
> Hi,
> This is OT but I'm sure many of you have used piezo microphones sometimes.
> I've often connected a piezo transducer to the microphone input of my
> computer (and other computers) by simply soldering the two wires to the T
> and S of a minijack plug, and it works just fine and my soundcard hasn't
> suffered any damage (apparently at least).
> However, I am concerned that a strong sound input (e.g. hitting the piezo
> transducer with with fair strength) may actually generate a voltage peak
> (thought only for a short time) capable of damaging the soundcard, couldn't
> it?
> Also, a friend of mine did the same with his Macbook and his headphones
> output has stopped working (may be just a coincidence though).
> Is there an easy way to make it safer? I seem to remember I had read
> somewhere (can't find it) about connecting a 1MOhm resistor in parallel...
> woudl that do the trick?
> thanks
> m.
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