Many factory equipped electric acoustic guitars have a preamp installed on the rim of the guitar giving the performing guitarist control of their sound at their fingertips. But few owners of vintage or boutique guitars are willing to perform such modifications to their expensive instruments. Hence, the internally mounted pre-amp and the inside the soundhole controls were born.
Back in the day, there were no such beasts. You had a pickup in your guitar and the pre-amp was the box you plugged into.
Those outboard preamps kept advancing with the times. So, even if your guitar had an internally mounted preamp (usually with limited controls, if any at all), you still might plug into one of these boxes to give you the control you need at your fingertips.
And, since you were going to have to plug into a box anyway (a direct box, otherwise known as a D.I. box, use to match the impedance of the input to the mixing board) here was a great opportunity to put some additional tone modifying or trouble eliminating circuitry. Therefore many of today’s outboard systems include a low impedance XLR output in addition to the standard ¼” high impedance output used for guitar amps.
Since these outboard preamps are active, they require power. Most are battery powered with the option of using an adaptor. Some are also capable of using phantom power provided through the XLR cable from the mixing board, but beware; many semi-pro mixing boards do not provide phantom power…so keep fresh batteries or the adapter close at hand.
All the advanced stuff that you find on modern onboard systems were most likely initially designed and refined for an outboard system; and it is most likely were you find new developments in acoustic guitar sound processing long before manufactures start including in their guitars.
The obvious kind of controls that you would find on outboard preamps would be a volume control and an EQ of some sort. The EQ might be just separate bass and treble controls, or perhaps have the addition of a mid control. On some units the mid control is parametric control allowing the user to select the actual frequency that gets boost or cut. Other units have more than one parametric mid control.
Since feedback is a common ailment of the amplified, some units feature automatic feedback control. Basically, this is a parametric EQ that finds the offending frequency itself and removes if from the output.
In addition to tone shaping capabilities, some preamps include compression and/or limiting. In simplest terms, loud parts (such as aggressive strumming) are reduced in volume to allow softer passages (such as fingerpicked parts) to be heard above the fray.
Some units include effects that are commonly used acoustic guitars, such as chorus, echo and reverb and the appropriate control over their parameters.
And some have a built-in tuner.
And some have all of the above.
One of the more recent developments is manipulating the signal of the guitar to match the signal of how the guitar would sound if it were mic’d. Then this manipulated signal could be used alone or mixed back with the original signal. These systems have been gaining high praise from some of the most influential acoustic players and the most discriminating ears in the business. In fact, they sound so good that they can be used in the studio without anyone knowing that the acoustic guitar was recorded direct!
And like all the other outboard preamps, all you need is one unit and you can use it with all you pickup equipped guitars which is nice since the better units are a little pricey.
The result of the digital revolution goes a little deeper than just modeling: Some of these new preamps are programmable. Different tone, volume, effects, and models can be stored for instant recall, as can patches for different guitars that use different pickup systems. Hey, it’s 2011:&nb
sp;we may not have the flying cars we were promised as a kid, but at least technology has provided us this.
Jake Kelly is a man on the constant search for enlightenment, if anyone finds it let him know so he can get some. For more of this hombre’s ramblings and the rest of L2P check out L2Pbandspace and L2Pnet.com.
Originally posted 2011-02-22 22:13:00.