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Permalink Reply by Doc Oakroot on April 28, 2009 at 12:46am

More or less, a preamp raises a microphone level signal to a line level signal. The power amp which drives the speakers is expecting a line level signal. Generally, a guitar amp has a preamp built in. So does each channel in a mixing board.

Production guitars with piezo pickups usually have a preamp built in to the guitar (which is why you have to put a battery in those gutiars).

BUT... that description actually misses the point, lol.

Preamps allow you to do things that you could not do with passive (unpowered) electronics. These things include:

1. Matching impedance with poorly behaved pickup (like the piezo disks many of us use).

2. Detailed EQ (vs. the simple "tone" knob you can have with passive electronics)

3. Mixing several signals into a single signal - try that with passive electronic and you'll get a mess... humming ground loops etc.

As for a picture, preamps are usually built-in to other equipment, so you can't really get a pic. But there are some stand alone preamps - they mostly look like any other guitar stompbox.

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Permalink Reply by Roger Martin on April 28, 2009 at 1:12am

Thanks Doc,
I have a Dean flat top with a preamp built in,it stopped working about a year after I bought it and the bridge warped so bad I had to add a tail piece and do adjustments to be able to use the guitar.
The pickup problem I never got around to fixing so far.
Too many 4 corner guitars to build thats more fun to play with,,,,,

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Permalink Reply by Dan Sleep on April 28, 2009 at 3:20am

I started investigating pre-amps myself and ran across this site that has a pic of a home built pre-amp for a piezo transducer.

http://www.diyguitarist.com/Guitars/PiezoBuffer.htm

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Permalink Reply by Zeb on April 29, 2009 at 5:34am

A preamp is used for a few reasons. If you are using long wires to plug into your amp ,voltage drop can drop off the signal. A preamp can boost the signal enough to compensate for long lead wires. Also a preamp can have on board tone adjustments for distortion effects. Go to (www.runoffgroove.com) and listen to the types of effects to hear what I'm talking about. A single transistor in a buffer circuit can do an awful lot. J201's are the shit. Older technology very musical. Digital can be abrupt and harsh.
You can buy kits to build, just the board or build your own. Most use a 9 volt battery so you won't electrocute yourself.
I have built preamps and boosters. Cool stuff. Great stuff to play with on a crappy rainy day. Enjoy the journey.. Chuck

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Permalink Reply by Zeb on April 29, 2009 at 8:07am

www.windworld.com/products/pu_info.htm#preamp This is a link to experimental instruments. Some cool stuff here. Some articles on piezos ,preamps and pickups oh my. Piezos ,preamps and pick ups oh my. Enjoy the path.
Yellow brick Chuck

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