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So, Did I Go Too Far?

I finished my second build last week. A three-string fretted CBG. I went to Gitty for piezo disk. I saw that they had 12 mm, 20 mm and 27 mm. I figured "What the heck, isn't bigger better?" so I opted for the big 27 mm pieces.I bored a countersink in the side of the neck (inside the box) and mounted the piezo in a bed of silicon seal top and bottom.

I'm feeding the piezo into one of the small 2.5 watt amplifiers I built into a spare cigar box. When I play my original frettless CBT into the amp, the sound is good (not too loud) and not too sensitive to my movements around the box (even with everything turned to the max). This one has a single 20 mm piezo.

When I crank up the volume knobs on my amp and new CBG (the one with the 27 mm disk) the amp picks up every stray movement of my body and hands. I slide my hand across the body of the box and it is amplified noticeably. I can turn down the pot on the CBG to reduce this unwanted sound, but, of course, give up string volume.

My question is: Is the 27 mm disc noticeably more sensitive than a 20 mm unit? Should I look at adding more damping around the Piezo? Maybe encase it in soft leather or something? Should I remove it from its attachment to the neck and mount it in a less sensitive area?

I like the string volume of this CBG, but think I may have taken a wrong turn on either selecting the piezo or in my mounting scheme.

Thanks for any suggestion or insights you may have.

Tom T

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Permalink Reply by robert jones on November 16, 2014 at 2:23pm

No idea what that says Tom but I'm suddenly struck with a desire for Oktapodi Krasato, fresh crusty rolls and resinous white wine in the company of a dark haired voluptuous woman on a seaside terrace caressed by the rosemary scented breeze from the hills while luxuriating in the sun.

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Permalink Reply by Tom T on November 17, 2014 at 8:46am

You get it, Robert.

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Permalink Reply by Michael Fred Johnson on November 17, 2014 at 2:16am

Is that why I do it ?

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Permalink Reply by Mick Bradford on November 20, 2014 at 3:52am

The piezo generates a small voltage when vibrated or under mechanical stress. To use them in a CBG think of it this way; a AAA 1.5 volt DC battery when connected in series produces 3.0 volts DC at one half the current and when connected in parallel they produce 1.5 volts DC at twice the current. When connected to an external amplifier the current requirement is negligible but the generated voltage is twice as much. One should be sufficient, but try two or three in series or parallel and decide for yourself which method is suitable for your situation.

Piezo devices have many uses in everyday items around your home and work:

Most smoke alarms use them to produce an earsplitting sound when activated by sensors when detecting smoke or carbon-monoxide gases.
Butane cigarette lighters
Igniters for your Bar-B-Q; hot water heaters; stove-tops and ovens
Vibration sensors in security systems
Frequency determining devices in computers, communications equipment, watches and clocks, hospital equipment, etc.
Speakers, earphones and microphones