| Articles:
Electric Guitar Piezo Pickup Saddles & Bridges: The Basics |
| My name is Alan, and I'm an electric guitar
piezo bridge addict - and happy about it. I started out with the original hardtail
Fishman Powerbridge (the first model available locally), and have never looked back since.
Three out of my four 6-string electric guitars now have piezo equipped bridges, and they
have become an integral part of my sound and playing. In this series of articles, I'm going to take a look at all things piezo:
what they are, how they work, what you can do with them, amplification and FX, some ideas
and sound samples and some pretty advanced applications. |
A bridge fitted with piezo saddles. |
The Basics
These days, nearly every electric guitar manufacturer is
offering at least one model that is fitted with piezos. A wide range of manufacturers are
now offering replacement saddles or bridges for electric guitar: Graph Tech, RMC, Mike
Christian, Fishman, L.R. Baggs, Schaller and more.
What are piezo pickups?
Piezoelectric pickups are best known as the undersaddle pickups used to amplify
acoustic guitars. Sensing mostly the vibrations coming directly from the strings
themselves, they give a relatively pure acoustic tone. While the lack of of the acoustic's
body resonance and tone make the piezo sound a little sterile in comparison to a mic'ed
acoustic guitar, the excellent resistance to feedback makes them ideal for live
amplification.
Unlike the magnetic pickups used for electric guitars, piezos
are very good at sensing higher frequency sounds, making them ideal for acoustic guitar
applications, which have a higher proportion of the upper frequency sound than their
electric counterparts. As they work with pressure rather than magnetism, they are also
well suited to non-magnetic strings, such as bronze or even nylon.
How do they work?
Piezo pickups are formed from a crystal or ceramic material, which produces
electricity when stressed. In our application, the stressing comes from string vibration.
The piezo element senses the small changes in pressure as the string vibrates, and
produces alternating current.
In an electric guitar piezo saddle, the piezoelectric element
is embedded in the saddle itself, rather than under it as with most acoustic pickups. Due
to piezo crystals and ceramics being brittle, the string itself cannot rest directly on
the element, so manufacturers either fit the element between a piece of metal and the
rest of the saddle, or in the case of the Graph Tech GHOST saddles, embed the element in
the material of the saddle itself.
Why use them on an electric guitar?
Good question, Tonto. Primarily to make it sound like an amplified acoustic guitar.
Less obviously, but more importantly, to use piezo and conventional sounds blended
together - more on this later in this series of articles. There are some advanced
applications like MIDIguitar and guitar modelling too.
13-pin madness
Piezo saddles are ideal for hexaphonic outputs, where each string is fed to a
separate output, allowing them to be used for 13-pin guitar applications such as MIDI
guitar (guitar synths) and Roland's VG (Virtual Guitar) modelling technology. I'll get
into detail on this in a later article, methinks.Similar
to the VG, Line 6 Variax modelling guitars use piezo pickups, but Line 6 have not seen fit
to supply the guitarist with the standard 13-pin output or a mixed analogue
"acoustic" piezo output. Oh, well...
Hexaphonic audio
Here's one for the "Mad Scientist" guitarists amongst us (who
me?). Take a 13-pin output, plug into a "breakout box" such as the RMC model,
and have the output from each string separate to process, amplify, pan and mix in any way
your fevered imagination can come up with. Again, more on this later. |
13-pin socket & mounting panel. The socket can
be mounted without the panel to reduce size.
|
What you need
Piezo saddles
The first item on the shopping list is the set of piezo saddles (you'd think this
was self evident, but having dealt with guitarists for many moons, I take no chances). As
already mentioned, these are available from Graph Tech, RMC and others. |
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Preamplifier
With any piezo system, acoustic or electric, a preamplifier is essential
to get a decent tone. Piezo pickups are very high output impedance devices (often higher
than two Meg Ohm) and do not play nicely with most amps/input circuitry. They do work
without, but sound very thin and scratchy. The preamp also has to be mounted as close as
possible to the pickups (usually in the guitar itself - they are usually quite small) to
prevent major tone loss to the cable. |
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Controls
This varies depending on what you want and what is included in the preamp you use.
The Graph Tech GHOST in particular is great in that the system is modular - you only buy
and fit the options you want. Be warned though, there are usually enough options to allow
you to go nuts and you can end up with a guitar looking more at home in a cockpit than on
stage.
At it's very simplest, a single volume control (usually
taking the place of a tone control) does the job pretty well. This way, your guitar looks
stock, and if you want the piezo or the magnetic sound alone, you just dial the volume
down on the other. To move up from there a 3-way mini toggle switch is nice as a
piezo/both/magnetic selector for faster changes - if you don't mind having the extra
switch on your guitar.
Power supply
The preamp needs some sort of power to work. Usually this takes the form of a 9V
battery fitted inside the guitar. Power on/off switching is usually via a switch on the
output socket. If you have the additional 13-pin circuitry, phantom power is supplied from
your 13-pin device (such as your Axon guitar synth, a Roland VG or Roland guitar synth)
via the cable.
If you have other active circuitry that requires power, such
as active pickups or a mid boost circuit, these can be powered from the same supply. Just
don't expect extended battery life if you have active pickups, active tone, acoustic
preamp and a hexaphonic preamp all running off one battery. This is when phantom power
becomes a necessity.
Hex options
If you want a 13-pin output from your guitar as well, you'll need to fit a
hexaphonic preamp. Note that not every piezo saddle manufacturer supplies this option, so
if you want to go this route, you have to make sure it's available.Outputs
Usually the guitar's output socket is changed for a stereo one, which
allows you to use a stereo cable to keep the magnetic and piezo signals separate. When
using a normal guitar cable, the preamp usually mixes the two signals together.
If using a 13-pin system, it is often possible to send the
piezo signal down the 13-pin cable - most 13-pin devices have an output to connect this to
other equipment. The normal magnetic signal is then accessed via an ordinary cable from
the guitar's jack.
Some (Guilty, your honour!) prefer to keep all the signals
discrete (separate) and will use two mono sockets for the piezo and magnetic signals. This
makes for a more cumbersome cable arrangement, but means that you can use any standard
guitar cables. |
Believe it or not, but this tiny circuit is the
Graph Tech Acoustaphonic preamp circuit with the Hexpander preamp piggybacked on the top.
The saddle in foreground is the standard USA Strat size.
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Fitting them
If you're not a handy person, or have a phobia of taking the occasional power tool to your
favourite instrument, this is not something you should do yourself - take it to a
professional. While many systems are relatively simple to install with some knowledge,
virtually every installation is different and there are times when holes may need to be
drilled or routed to make things fit.
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