Tech Tip:Combining Piezo & Magnetic Pickups

How To Thicken a Single Guitar Sound in Two Ways: One Live, One Overdubbed


By Craig Anderton, Editor in Chief, Harmony Central


Many modern electric guitars come with piezos built in, and I've gravitated to them because I've always considered a piezo an extra feature worth its weight in gold and one that doesn't significantly change the layout of your guitar or otherwise impact the sound. It's just a bit of circuitry, usually built into the bridge. The Fender Deluxe Nashville Power Telecaster includes one, and you can imagine how an acoustic quality might benefit the Tele sound. But several Les Pauls contain them, including the Alex Lifeson Les Paul Axcess and the Dark Fire.

Many guitars even have their identity wrapped up in the combined piezo/magnetic combination, including the PRS 2011 Hollowbody II; many Parker models including Nightfly, Maxx Fly, Dragonfly, and Radial; Italia Mondial II; and most of the Music Man John Petrucci models. Companies like Fishman, L.R. Baggs, and Graph-Tech all make aftermarket bridges for Strats, Teles, Tune-o-Matics, and more, allowing you to "piezo-ize" virtually any guitar. The photo to the right shows an L.R. Baggs T-Bridge installed on a Les Paul. Its piezo circuitry is virtually invisible to the eye and doesn't disturb the original aesthetic of a traditional Les Paul.


Being Cable Able

If you have both a magnetic and piezo output, you can process them separately for a rich, layered sound created at the core, well in front of what a stereo split in your chorus or delay can do. To do this, you need to know whether your guitar's piezo/magnetic system splits the signal as well as blends it. In the case of the former, a stereo jack is used, and you need a stereo Y cable to send the signal to two different destinations.

Keep in mind that you can blend the piezo/magnetic sound at the guitar—varying the balance between the two pickup systems—but what we're talking about here is a split signal that can, among other things, create the illusion that two guitarists are playing.

For example, in rock and electric-blues playing, you can take the magnetic output and run it through a wah-wah, while leaving the piezo output fairly dry and unprocessed. This will create the illusion of an acoustic guitar doubling the wah part. Obviously, sending the signal to two different amps—one an acoustic combo, the other an electric guitar amp—further heightens the separation effect. The two-amp sound—even with no spatial separation—will sound like a blended sound. But by using two amps, each specialized for the task, you're creating a blend with much more independence and articulation than you would if you had blended the signals inside the guitar and onto the single output of a mono cable.


The Reverb of an Overdub


And now the answer to the "overdub guitar" riddle. It's a neat trick that's subtle enough to turn the heads of the attentive, but won't distract from the musical impact of the principal signal.

Start by recording a melodic line onto one track. Then double the line by playing it onto a second track as an overdub, but take care not to play it exactly like the original. Take a few liberties with the tempo and the articulation (such as sliding into a note instead of striking it and so on) and maybe even vary the choice of a note or two (but do this sparingly, as it will come back to "haunt" you).

Here's the important part: Run the second part through a reverb and have only the effected signal sound against the original guitar track. Typically you'd use the little-understood pre aux send for this. The "pre" in this case refers to the fact that the level going out to the aux send jack occurs before, and is therefore not influenced by, the channel's volume fader. The signal level is pre-determined at the channel's trim control. Moving the fader up increases the dry-to-wet ratio and moving the fader down decreases it (or increases the wet-to-dry ratio, which is the same thing). In other words, move the fader all the way down and you're left with just the ghostly effect sound—100 percent effect. And this is precisely what we want here. The pre aux send effect with the fader at zero lets just the effect of the doubled guitar through. Combined with the original track, it sounds like "wrong-note reverb" where the effect is misbehaving and deviating from the original signal. This technique is great for atmospheric effects.