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From one idea to the next, here's the back story: I'm currently taking an interest in sound design, and read an article about making sound effects from recording via contact microphones. I already have a portable stereo recorder which is the Zoom H2n, which has a line/mic input (which is stereo), which has 2.5v plug-in power which I can switch on if required.

Now I want to make my own stereo piezo mic and plug it into my recorder, but do you think I need a pre-amp when the Zoom h2N has it's own mic gain control? I gather the impedence of piezos is as much as 50KOhm and would be too quiet if wired directly to a line/mic input. The ones at Maplin (where I might source my components) are 450Ohm-800Ohm. If I need the extra preamp then I'd like to see if I can use the plug-in power from my recorder to power a home-made stereo preamp. I've seen the Alex Rice preamp circuit design, but this is made for 48v Phantom power not 2.5v. I presume I will need a complete exchange of components as well as adapt it for stereo if don't just make two of them....so, is 2.5v enough to amplify a piezo contact mic signal?

For the record I'm no good at designing circuits, I'm just good at assembling them.

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migrated from sound.stackexchange.com Oct 6 '17 at 20:35

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    \$\begingroup\$ It says LINE IN with a microphone symbol next to it. I presume but not sure it handles both and intelligently senses what level the input is. I looked through the manual thoroughly but it doesn't cover that level of detail. This is bit electronical, I'm quite new to stackexchange, I joined stack overflow first and music practice and theory. Hoping that some sound-recording enthusiasts have already attempted my idea. I'd just like to this in-line without using a battery or other separate power source. Is it cool to just copy my question over to the electronics one or does it need to be moved? \$\endgroup\$ – Olly Oct 6 '17 at 19:31
  • \$\begingroup\$ "It says LINE IN with a microphone symbol next to it. I presume but not sure it handles both and intelligently senses what level the input is." I think that's right. "Is it cool to just copy my question over to the electronics one or does it need to be moved?" I THINK so. But I've never tried before. \$\endgroup\$ – user162154 Oct 6 '17 at 19:49
  • \$\begingroup\$ I'm not confident enough in this answer to call it an answer, but I don't think amplification is the issue here; impedance matching is. You should be able to get by with an impedance-matching transformer. Contact mics are often used for pickups, and are very close to a Hi-Z input; a direct box for connecting guitars to line inputs would likely work. FWIW I field-record contact mics into a Tascam GT-R1 for this very reason - it's a handheld guitar recorder. \$\endgroup\$ – brhfl Oct 6 '17 at 21:13

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