So How Do I Choose a PreAmp? – Joe Bigham

Since you read last month’s article about pick-ups, you may have rushed out to try a few and may have even bought one. Now, you may be saying to yourself, “What am I missing?”. Or maybe you’ve used your new system in live applications, but are not completely satisfied with the tone. A preamp may be the solution to all of your quandaries.

What does a preamp do?

First, it boosts the signal level significantly. Many acoustic amplifiers and PA systems “look” for a signal that has some juice behind it.

When the soundman boosts the signal of a non-preamped signal two things happen that are far from pleasant: the gain added by the soundman also raises the level of noise, whether it be hiss or hum caused by RF interference, and the signal will sound thin (lacking in bass and mids). The thin sound is caused by an impedance mismatch (impedance refers to resistance values measured in ohms). Piezo pickups and other styles of acoustic pickups typically have an extremely high resistance (thousands of ohms), while PA systems are always looking for low impedance sources (hundreds of ohms or less). Preamps boost the signal level of the source, and alter the impedance to match PA systems or acoustic amplifiers.

Secondly, all outboard preamps and many onboard (installed in the guitar) preamps offer varying levels of tone control. These range from simple treble and bass boosts, to finely tuned parametric equalizers. If you feel that your pickup tone (regardless of amplification) is well balanced, but lacks just a little bit of lower-mid character, you can find the frequency that needs the boost. These tone controls can also be used to eliminate feedback. Most acoustic guitars tend to feedback in the lower range at the same frequency as a G or A note on the low end of the guitar. By cutting back bass, or finding the thin band of offensive frequencies, you can “tune” out the feedback problem.

Third, many preamps also act as DI boxes. A DI box allows you to send you signal long distances by a microphone cable as opposed to a regular instrument cable. Microphone cables are less prone to RF interference and are favored by soundmen because they easily plug into any on-stage snakes (large cabling boxes that carry almost all signal to the soundboard). In fact, any instrument that is not mic’ed into the PA has to run into a DI box at some point.

Lastly, preamps give you the opportunity to mix multiple signal sources, and then apply effects to all of these signals, or individual signals via effects loops. If you have both a piezo pickup and internal microphone in your instrument, you would blend both signals at the preamp, and then add your favorite chorus or reverb to both channels. This way, you are controlling the signal that ultimately goes to the soundman or amplifier.

Types of preamps

There are as many variations on preamps as there are pickup systems. They range from simple guitar installed models with no adjustable EQ, to full blown units that offer mixing, EQ, DI, and effects capabilities. Once you have decided the amount of control that you want over preamp-processing, the options seem less confusing.

If you already have an acoustic amplifier that you use as an on-stage monitor, a simple jack-preamp like the Fishman Powerjack or the B-band A-2 will work well for you.

If you want to be able to adjust volume or EQ from your guitar, the Fishman Prefix system, or Takamine preamps (some with onboard tuner and digital reverb) would suit you well. If you do not wish to alter the construction of your guitar, the Fishman G-2 or L.R. Baggs Gig-Pro allow EQ and level control from a beltpack unit. The L.R. Baggs Para-Acoustic DI, and Fishman Dual Parametric DI offer preamp, EQ, and DI abilities from a floor unit the same size as a stomp box. Lastly, for those who require all of the above, plus mixing capabilities for more complex pickup systems, the Raven Lab’s Master Blender, B-Band Entity, and Fishman Blender offer EQ’s for individual channels, individual and master effects loops and the most gain available from any of the preamps mentioned.
Your sound, only louder

By finding the pickup system right for you, and a matching preamp to fine tune that sound, you will be able to create a great acoustic tone regardless of the venue. You can even combine onboard preamps with outboard preamps to maximize your tone. Members of our staff have had extensive experience with these systems here in the store, and around various venues ranging from churches, to the Sheldon, to the Pageant. If you are looking to fine tune your amplified sound, there is sure to be a preamp that will provide you with the control and convenience you need.

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