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It’s a Guitar, Not a Duck

Hello Troubadourians! In San Diego the majority of performing musicians are solo artists who play the guitar, usually an acoustic guitar. While some elite acoustic artists can, and do, insist on performing using only a microphone to amplify their instruments, it is difficult to isolate and direct the acoustic output of an acoustic guitar into a microphone on a noisy stage. So, most of us have to “plug in” our instruments when we perform. Plugging-in requires that the guitar has some sort if pickup installed into it. The most common pickup is an under saddle Piezo transducer.

Piezo (pronounced pie’-zo or pee-A-zo) pickups are interesting devices in either crystal or film form, which can operate as either a pickup or as a speaker. Derived from quartz, piezos, when mechanically distorted – as by a vibrating guitar string – will produce a voltage that can be converted to sound by an amplifier. Conversely, when a piezo is stimulated by a voltage, it will produce a corresponding sound. Many high-frequency transducers found in PA cabinets contain piezo elements. Seems like a really clever device doesn’t it? Well, it is really, but there is a down side. In addition to the ability to efficiently amplify (or “transduce”) sounds from practically any source, piezos are equally adept at amplifying their own particular sonic characteristics. Whether functioning as a pickup or as a speaker, piezos are often associated with possessing a “plastic” or “quacky” character. This phenomenon was especially prevalent in early guitar pickups made by manufacturers such as Barcus-Berry, Fishman, and L.R.Baggs.

More modern piezo transducers produced by the above manufacturers as well as numerous others are far less likely to be as overtly quacky as they used to be but discerning listeners can still detect some quackyiness in even the best pickup systems. So, what can be done about a quacking guitar? Well, the first thing is to use a high quality preamp between the piezo pickup and whatever amplifier you are plugging into. The preamp will help match the output impedance of the piezo with the input impedance of the amplifier. This will raise the level of the “good signal” produced by your guitar above the “quacky signal” produced by the piezo amplifying itself. How the preamp does this magic is complicated to explain and involves lots of math that you aren’t interested in, so just be happy that it works. Many guitars have this preamp built in from the manufacturer and it is likely tuned to respond well with the piezo pickup it is mated with. If your guitar doesn’t have a built-in preamp, you can use an external preamp or have one installed in your guitar.

External preamps can be simple or complex. An example of a simple preamp is a Micro Amp pedal from MXR; one knob and a switch. More elaborate preamps are available from Fishman, L.R.Baggs, Seymour Duncan, and others and many feature digitally enhanced “voicings” for particular guitar body sizes and types as well as other instruments, and many have digitally modeled the sonic characteristics of high-end studio microphones, which can be blended with the sound of your guitar’s piezo pickup. Internal preamps such as the Fishman PowerJack can be installed in your guitar with little alteration of the guitar.
Equalization, or EQ, can also be utilized in addition to using a preamp. If your guitar has a built-in preamp, chances are that it includes at least some basic EQ capability. This may be as simple as a treble/bass control or as complex as a multi-band graphic EQ. Just as a preamp can be external, so can your EQ. Most of the complex preamps above also include some type of EQ. Dedicated stand-alone Equalizers are also available from companies such as MXR, L.R.Baggs, Fishman, Boss, and DigiTech. Most of these are “graphic” type EQs, so named because the frequencies are represented graphically with sliders that control the cut/boost of their associated frequency band. Other types of EQ are shelving, parametric, and quasi-parametric. (I’ll explain all EQ types in a later article.)

What if my guitar doesn’t have a preamp or an EQ? Good question. My Collings D2H didn’t have any electronics at all when I bought it. Over time, I have added an under saddle piezo pickup, a preamp, and a Volume/EQ control to the guitar; I also use a digitally modeled preamp, a graphic EQ, and a booster preamp on my pedalboard. I run a signal direct into the house PA and a parallel signal into an onstage amplifier so that I can monitor my guitar on stage. I use that much gear because I play lead guitar in my band and I also play loud to compete with the drums, bass, and violin. The louder you need to play, the more critical your gear choices become and the more “stages” of amplification and EQ are required to achieve the desired level while maintaining the “normalness” of your guitar sound.

So, what does all this have to do with a quacking guitar? Well, the purpose of all of this preamping and EQ-ing to get our guitars to sound natural or normal. In fact, equalization is often referred to as “normalization” in England and Europe. We control – or alter – the EQ to make our guitars sound normal instead of quacky. Everything in my guitar and on my pedalboard is utilized to make my guitar sound as normal – as much like itself – as it can in a live environment. Will you need three preamps and two EQs like I use to make your guitar sound normal and not quacky? Probably not. Usually, just reducing the midrange on your onboard preamp will get rid of most of the ‘quack’. If you are a solo performer, you can make your guitar sound natural often with only the preamp/EQ that is built into the guitar and careful EQ-ing on the PA with a surgical EQ reduction around 2K. Use care when applying EQ, though. You don’t want to take all of the guitarness out with the quackyiness.

Need to know? Just ask… Charlie (ask.charlie@hotmail.com)

  • September 2016

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