I have been told that I’m pretty opinionated about a few things. One of those opinions is my almost universal disdain for the piezo disk as an instrument pickup. This is partially hypocritical, I’ve used them in the past, I’ll likely use them in the future, but I’m not typically pleased with the results. Most piezo disk applications sound thin and brittle to my ears and have a shrieking overtone to them that feels like a dentist drill on my last nerve. However, you can’t argue the facts that piezo elements are:
- Easy to fit in tight spaces
- Sound more “acoustic”
- Can be used with bronze phosphor strings
And for those facts alone, sometimes they are the best option. However in these situations, I must insist that all piezo elements, both disc and rod varieties be used in conjunction with a preamp or preamplifier.
Most amplifiers with the exception of a relative few designed specifically for piezo equipped “acoustic” instruments, are designed for a range of impedance (resistance) of a magnetic pickup. The impedance of piezo discs are comparatively much lower. This leads to a mismatch between what kind of signal the amplifier is designed to handle and what it is being given. The result is that thin and brittle sound that I’ve come to resent with such fervor.
The solution is to use a battery-powered series of capacitors to buffer the output of the piezo element to be closer to what the amplifier is expecting. This is also known as a preamplifier. While these devices won’t completely eliminate the sound characteristics that are inherent to piezo elements, to my ears they are least make things tolerable, and are thus required equipment.
For those reading that are dedicated to the cigar box variety of instruments, you could argue that it’s a cigar box and it’s only going to sound so good no matter what. To a certain extent you are right, but there is a difference between lo-fi and bad. The addition of a preamp isn’t going to change the character of the sound, but it will go a long way to controlling the frequencies that lead to listening fatigue.