Some of what you wanted to
know regarding Active Pre-Amps


Dana B. Teague
04/03/2015

Whether you “need” a preamp or not is quite a debatable topic.  How many Strat, Tele, Jazz Bass, P-Bass, Les Paul, players hunger for active electronics?  There are an awful lot of players (including me) who have gotten used to passive guitars and passive basses.

AP or non AP, the question(s) are usually:

  1. Is the control cavity big enough for the battery and the preamp?
  2. Can a configuration be found that matches the number of holes already in the instrument w/o modification?
  3. What gigging or tone problem are you hoping to solve, or what new capability are you trying to add?

Adding an active preamp gets you some or all of the following.  

  1. The ability to change your Bass/(Mid)/Treble to taste from your instrument.. A lot of players adjust to different venues by tweaking their amps. .Some players prefer to make adjustments from the instrument and leave the amp alone.
  2. The ability to set one tone with the amp with the bass in passive mode, then switch to active on the instrument (via and active/passive or AP switch) for a boosted volume or different tone for soloing, or to go from a fingerstyle EQ to a slap/pop eq, which is usually boosted bass, boosted treble.
  3. An active preamp serves as a buffer (Like a Lehle Sunday Driver) between passive pickups and effect pedals which may be in the chain from instrument to amp. Effects pedals, especially vintage ones, have a nasty habit of loading down single coil pickups and removing some of the sparkle.  A preamp buffers the high impedance single coil pickups by giving them a nice high impedance to work into, while providing an output that is low impedance, which can drive long cables and lots of signal sucking effects without breaking a sweat.

The downsides of a preamp are some or all of the following:

  1. They take batteries, which can go bad at the worst possible times.  An AP (Active/Passive) equipped instrument can always be played in passive mode should you find yourself without a spare 9V battery.
  2. Plugging a cord into the jack on the instrument is what powers up the preamp.  There is always a loud pop when you plug in a live cable.  When the jack gets worn, and it will, wiggling the plug will make unpleasant and loud popping noises.
  3. Pickups that are not perfectly quiet from the get go, like single coil strat pickups, are even nosier when amplified and buffered.  Preamps work best on hum cancelling pickups.

The AP and non AP version of Bartolini’s harnesses do EXACTLY the same thing.  The AP simply adds the capability (via pull pot on the volume control) to switch between active and passive (preamp bypassed) modes.