When talking about acoustic guitar pickups, preamps, direct boxes and the signal path your electric acoustic transverses, we would be remiss if we didn’t mention the breed of amplifiers designed for acoustic instruments.

 

The name amplifier is slightly deceptive. It is a generic term for a combination of a preamp, amplifier and speaker(s). And…many of these acoustic amplifiers have a XLR post preamp output, eliminating the need for a direct box.
 

Obviously, since the amplifier contains a preamp, an outboard stand alone preamp isn’t needed. The tone shaping and contouring can be handled on the amp itself.
 

The preamp on the amplifier, since it was designed for acoustic instruments, will most likely feature the same acoustic-friendly controls that help fight the acoustic guitar’s arch nemesis: feedback.   Some of these controls might be parametic EQs that allow you to notch out troublesome frequencies while leaving the bulk of the frequencies around them relatively unaffected, and/or a phase switch (not to be confused with the phase shifter guitar effect), which reverses the signal. 
 

There are better explanations on why this works to reduce feedback elsewhere, but here’s a simple one: The feedback signal your guitar is producing is a “peaks and valleys” sound wave, and that feedback coming from your amplifier’s speaker is also a “peaks and valleys” sound wave. If your guitar is feeding back because it is hit with a “peak” from the speaker at the same time as producing one, reversing the “peak” to a “valley” and vice/versa from the sound wave from the speaker could cure the problem. Instead of having two mountains on top of each other, the mountain is cancelled out by the valley.
 

Other features the amp might have are the more common acoustic guitar effects, such as reverb, chorus and compression, and the controls of their parameters.
 

Since so much of the beauty of an acoustic guitar is the shimmering higher frequencies, many of these amps feature tweeters in addition to the low/mid driver. Sometimes the amplifier is bi-amped, giving the high frequence driver its own amplifier.
 
In short, these amplifiers are more along the line of a mini self-contained P.A. system than a conventional electric guitar amplifier. So much so that they often contain a separate channel for a conventional microphone, so a singer songwriter could plug their guitar and mic into one of these in a club or coffee house and be good to cover 50-100 people with no other sound equipment needed.
 

Players that have a pickup/mic system with a separate output for each signal will instantly recognize the benefits of the microphone channel, as each of those signals can be dialed in separately.
 

Devices, such as tuners or modeling pedals, could be use inline before the amplifier. In fact, some soundmen might prefer that the guitar is run into the tuner and/or modeler and then into a direct box, where the signal is split with one side going to the P.A. and the other to your amplifier. The idea being that sound requirements for the house is different than the sound requirements on stage where specific (but beautiful) frequencies are squelched and sacrificed for the sake of feedback reduction.
 

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 2011-02-24 20:51:34.