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Preamp Question

Discussion in 'Pickups & Electronics [BG]' started by gimp, Dec 23, 2013.

  1. gimp


    Jan 13, 2011
    Catonsville, MD
    My old workhorse precision bass currently has an older set of EMG active pickups in it, and I'm strongly considering swapping them out for passives (P-46). Since the body is already routed for a battery, I was also thinking about installing a preamp.

    So my questions are:
    1. Are there any preamps that have a full bypass (passive/active)?
    2. Worth it with the P-46?

  2. Active/passive switching is a wiring choice. It can be done with any preamp.

    High impedance passive pickups jive with a standard 1M Ohm input impedance. Any preamp with this specification, or higher, will work. Some of EMG's preamps have 500k Ohm input impedances. These are ok, but there will be a bit of loading on the pickups, resulting in a slight loss of treble.

    Though uncommon, some preamps on the market have two or more inputs. These should be avoided on single-pickup basses.
  3. gimp


    Jan 13, 2011
    Catonsville, MD
    Awesome - great info! Thanks.
  4. RobbieK


    Jun 14, 2003
    A nice mod is to get your tech to wire an attenuator on the ouput of the pre (but inside the true bypass switch). Most pres have at least a little gain, and when you switch between active and passive modes, you get an annoying volume jump. A trimpot hot glued somewhere accessibile should do the trick. It's very handy if you go from active to passive sounds from one song to the next or if you use the active, say, for slap and you need to switch mid-song. A few times, I've even mounted one on the side fo the electronics cavity and drilled a little hole in the cover so you can adjust this with a small screwdriver.