PRE-AMP????

A preamp in a bass:

• functions as a line buffer that turns the high impedance signal of passive pickups into a low impedance signal - prevents loss of highs when the signal goes through the cable
• has an EQ that can cut AND boost certain frequencies. A passive EQ can only cut frequencies.
• some amplify the signal a bit, but most do not so you can use active and passive modes without volume changes.

A Preamp in an amp does basically the same thing.
But here it is necessary to amplify the signal up to line level for the poweramp and often has additional circuits for EQ, effects loops, D.I. out, etc.

 

A preamp in general, boost your signal level to match what you would consider optimum in refrence to proper gain setting. In other words, every bass's output signal is different, to compensate that, amplifier manufacturer has to have a preamp to adjust the input for every types of bass. By doing that, we avoid distortion and noise if it's set correctly. That was the original intention of a pre-amp(which is also an amplifier that amplify in a smaller scale). However, the way a preamp has been design, using tube, transistor, etc; it has create a small distortion on the signal that in ordinary human ear we would only concieved as the sound being fatter, or brighter etc. Which creates the warm sound we like so much.

That has been applied to the bass itself. So they install a "preamp" within the bass thus making it active electronic. Active Pick up is different however than active electronics.

With a preamp in your bass, your bass output level should be louder than a passive bass. You have more control of EQs(cut and boost, freq selection etc). Plus all the little gadget that should enhance your sound if used properlly.

Hope that helps.