Note #1: I may be able to send out one of these immediately, but usually I'll need anywhere from three to five days to assemble and test one. See the 'Ordering' page on the thaudio.com website for details.
Note #2: 02/2023: Many acoustic guitars made nowadays (if they come with onboard electronics) have preamps installed that shouldn't require an impedance-matching device like this one, either because they don't use piezo elements, or because they already do what this device does. The Piezo Buffer is meant to intercept a 'raw' signal from a piezo transducer before it reaches an amplifier or sound-system input.
Note #3: 02/2023: I ordered a new batch of enclosures. For these, the silkscreen on the top face now has 'TH Audio' under the logo at lower right. That's why the product photos look slightly different than the ones in the videos.
What is the Piezo Buffer?
The Piezo Buffer exists to address a very specific situation: you have a musical instrument, such as a mandolin, a double bass, or an acoustic guitar, equipped with a piezoelectric transducer of some sort, and you need to amplify the signal. But when you run the transducer straight into an amplifier, the result is unpleasant to listen to. Specifically, you probably hear a tinny, harsh tone with weak low-end response. That is most likely because of the impedance mismatch between the pickup and the amp. A buffer circuit can help.
Below are two videos about the Piezo Buffer. The first is a review by bassist Frode Berg. The second is from TH Audio (and really needs an update).
With the TH Audio Piezo Buffer, you'll most likely hear:
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the low frequencies that often go AWOL when you try to plug a piezo pickup into a traditional guitar or bass amplifier,
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less harshness in the high frequencies, and
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a smoother overall response.
The input impedance of the Piezo Buffer is ~= 10MegOhms, to accommodate the very high input impedance of piezoelectric transducers, which tends to be around 5 to 10 MegOhms. Fishman piezo pickups seem to like 10 MegOhms. Homemade transducers, like what you could make from the disc in a Radio Shack buzzer or piezo material from LMI, will respond well to 5 MegOhms but 10 is okay too.
The output signal of the Piezo Buffer won't necessarily be stronger or louder than the input; in fact, much of the time, the output signal will sound less loud. That's because the Piezo Buffer is, theoretically, a unity-gain device, in other words, a device with a gain value of 1, and as we know, 1 times x is, theoretically, x.
The output impedance of the Piezo Buffer is around 220 kOhms.
Note
As mentioned above in note #2: nowadays, many acoustic instruments, especially acoustic guitars, come with pickups and onboard preamps that often have tone and/or volume controls accessible on the outside of the instrument. You probably wouldn't need the Piezo Buffer for one of these - it's for pickups that aren't already being run through onboard preamps. Most of the time, you can find documentation that will tell you the output impedance of an onboard preamp. If it's listed in kOhms (kilo or thousands of Ohms), the Piezo Buffer probably won't be useful for that instrument. If the output impedance is listed in MegOhmns (mOhms / mega- or millions of Ohms), then the Piezo Buffer would probably be very useful.
Controls
Bright controls, you guessed it, the high-frequency response of the output.
Phase switches between unaltered phase and 180-degree phase inversion (can be useful for dealing with onstage feedback).
The footswitch mutes the signal - it is not a bypass.
Inputs and Outputs
The Piezo Buffer has a single 1/4" input and a single 1/4" output.
Power
The Piezo Buffer runs on a 9-Volt internal battery. To replace the battery, disconnect the unit and unscrew the back plate. Disconnect the existing battery from the battery terminals and lift it out of the enclosure. Connect the new battery to the terminals and reattach the back plate.
To run the unit on external power, use a 9V or 18V DC supply (center-negative). TH Audio does not recommend running the Piezo Buffer Mini on voltages greater than 18VDC.
The Piezo Buffer features:
- Hammond enclosure
- Metal film resistors, 1% tolerance
- Switchcraft jacks
- Heat-treated silkscreened graphics
All TH Audio pedals are handbuilt and tested in the United States.
