Combining Piezo and Magnetic Pickups

How to thicken a single guitar sound in two ways: one live, one overdubbed

By Jon Chappell

I have two tricks to thicken my guitar sound that are a little outside of the norm. When it comes time to add a little dimension to a guitar part, I always consider these two because in the first case, the resulting sound comes from one guitar that can be played live. The second trick involves an overdub, but there is still only one guitar that the listener hears. So in both cases, it’s only one guitar sound that makes it to the final output, but there’s an extra dimension that gives the listener a little something to think about. How do you overdub a guitar and still have just one, you ask? Read on to find out!

PROCESS YOUR PIEZO, MANGLE YOUR MAGNETICS

I took a look around at my main axes recently and realized that all of them have a piezo pickup—even the iconic solidbodies, like my Les Paul and my Telecaster. 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 change significantly the control 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 Les Paul Piezo, Dusk Tiger, and 2010 Standard.

Many guitars even have their identity wrapped up in the combined piezo/magentic combination, including the Michael Kelly Hybrid, Parker Fly, Hamer Duotone, Brian Moore C-90, and Godin LGX are but a few. Companies like Fishman, L.R. Baggs, Graph-Tech, and Stewart-MacDonald all make after-market 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.

Figure 1 shows the L.R. Baggs T-Bridge system uninstalled. It's a drop-in replacement for a Les Paul-style bridge, or any Gibson or other brand that uses the Tune-O-Matic.

Fig. 1. The L.R. Baggs T-bridge, a drop-in piezo replacement for a stock Tune-o-Matic, such as those found on Les Pauls.

Fishman makes a whole gamut of bridge replacements in the PowerBridge series. Figure 2 shows the unassuming front of a Tele-style PowerBridge, with individual saddle piezos. Figure 3 shows the underside, with a magnetic pickup installed. Lots of stuff going on there, but you'd never know it, as evidenced by the clean look of the Fender Nashville Tele shown in Figure 4.

Fig. 2. Looking frontward at the Fishman PowerBridge for a Tele.

Fig. 3. The underside of the Tele PowerBridge showing the works.

Fig. 4. The Fender Nashville Tele, with a Fishman PowerBridge sporting under-saddle piezos for that acoustic sound in a magnetic-equipped solidbody.

BEING CABLE ABLE

If you have both a magnetic and piezo output, you can process them separately, for a rich, layered sound that creates your sound 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 (Fig. 5) to send the signal to two different destinations.

Fig. 5. A stereo Y cable into the guitar's stereo jack is necessary to split the signal and send the piezo to one destination and the magnetic to the other.

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 taking 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. Or you can send the piezo sound straight to the mains--which is often the preferred way to route acoustic signals, as they don't need the tonal coloring of a guitar amp to achieve their ideal sound. If you use two amps on stage, placing the amp together will tighten the stereo image, separating them will widen the image. If the amps sit side-by-side, and the audience is back more than about 6 feet (which they certainly will be), you'll perceive no localized distance between the two.

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.

USE JUST 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 (see Fig. 6). 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.

Fig. 6. Use the Pre Aux Send to create a "ghost" reverb by putting the channel fader at minimum. Only the effected signal of the second guitar track gets through, combing itself with the original guitar track, but not matching it exactly.