![]() I don't get much feedback for the same volume level as a microphone would - and an easy solution to that, which doesn't affect the tone of the instrument, is to plug up the sound-holes which is routinely done for acoustic guitars. On my viola, it is about 1cm away from the bridge toward the tailpiece, centered under the strings where I find it gets the best sound. On my mandolin and nylon guitarlele, the piezo disc is under the top, as close to the bridge as I could reach. ![]() If you placed them on the tops, you'll have lost the isolation and feedback resistance, at which point you lose the usual advantages of piezos and might as well use a mic. AND I'm also giving the most likely solution to that problem, along with proof of concept. I answered the most likely reason why, which, for piezo pickups, is almost always impedance mismatch. It always sounds thin, harsh and aggressive. OP: the sound is horrible and I can't do anything about it. Or repurpose the 'talking' element of a talking greeting card. The piezoelectric elements themselves are cheap Chinesium discs you can get like 5 for a dollar. RAW = untouched sound of piezoelectric element directly into mixerĭI = passing through my DI before entering mixer.įor the electronics nerds: the DI was built using the NE5532 / TL072 op-amp chip, and is powered by phantom power from the mixer. Instruments: MDN = mandolin VLA = viola GTR = customized nylon-string guitarlele I will try and upload sound clips of my instruments using 1) raw piezo sound, and 2) using my custom-made DI.ĮDIT: Audio files uploaded at recorded using the USB interface of a Yamaha MG10XU analog mixer. Source: I've been spending time building op-amp based electrical circuits specifically for this purpose, to use on my mandolin and viola. Some manufacturers offer 1) piezoelectric elements specially engineered to have lower impedance, and 2) piezo-specific DI boxes. The signal is gone from the wire itself and there is no way to fix it with EQ because the recorded signal is tainted. In a simple sense, piezos physically lose a lot of the bass at the input connection because the physical connection between the high-impedance piezo and the low-impedance mixer input acts like a physical high-pass filter. This is true even of some very expensive violin bridge pickups. They are electrically considered capacitors and, for audio purposes, should have impedance in the range of many megaohms - while audio interfaces and DI boxes that you typically use have input impedance in the multi-kilo-ohms range. They put out a lot of voltage for a relatively small stress (example - the spark from a piezo-based cigarette lighter is pretty high voltage). Piezos, as you know, generate electricity from mechanical stress. That said, the main reason that piezo elements sound like shit most of the time is that most audio interfaces are not designed with piezos in mind. This is less of an issue when the element is fixed solidly to a surface to pick up sound. Many, if not most, piezo elements are of the type used in talking cards, where they are engineered to resonate more above 1kHz to make a clearly audible sound. They are in fact some of the most accurate sound capturing devices you can get. (Well-made) Piezo elements are extremely sensitive when attached to a surface. TLDR: The physical characteristics of typical piezoelectric elements and commonly used mixer inputs causes a natural high-pass filter that drops most of the lows below the kHz range, in the wired connection itself. Description in the edit at the bottom of this comment. I have built one myself and will try to upload clips when I am free, so keep an eye here over the next day or so. You need a DI with input impedance of 10 megaohms or so. Very few recording interfaces are designed to handle piezoelectric input. I know that I won't get an acoustic sound out of a pick-up but that's exactly my question: Why? What is it about the frequency response of pick-ups that makes them sound thin? Is it additional distortion? Or what's going on? Why can't I fix the sound with an EQ? It's like there is some sort of sound signature that's baked into the frequencies like some of esoteric vodoo magic that messes with the sound and that one cannot get rid of without magic.įinally something I can answer in depth!!! Answer: electrical impedance mismatch. There are some areas of the frequency spectrum that obviously stand out (like 1-3 kHz, usually) but taming them doesn't get me any closer to an acoustic sound. But when I dullen the sound it just gets, well, dull. I've always thought that if something sounded thin it had too much highs and too little lows. Great isolation with no feedback but the sound is horrible and I can't do anything about it. Recently, I've been working more and more with string players that use pick-ups. ![]()
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