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Preamp question.

Discussion in 'Pickups & Electronics [BG]' started by theonlyty, Oct 20, 2013.

  1. theonlyty


    Mar 8, 2013
    What's up everyone? First time posting,

    I have a question about preamps. I have a 2012 Fender P-bass special. (Seafoam green. So hot.) It has a master volume, blend between the p/j pickups, stacked bass and treble, and then a mid control. I never use the mid control.

    What would be the best preamp (2-band) to wire to the stacked pot? I also want to install a passive/active switch and make the existing mid pot a passive tone control. I have never tampered with any electronics in my basses, so I need some advice.

    Also, I really like the idea of Audere's z-mode switch. Could I install something like it on my bass?

    Thanks in advance!
  2. Any non pcb-mount preamp can be wired with concentric pots. Any single-input preamp can be wired with an active/passive switch.

    The existing mid pot most likely cannot be reused, as you will need a higher value for a passive tone control than what is currently being used for the preamp.

    Z-Mode switching, to my knowledge, is simply a variable impedance loading. That can be replicated with a switch and a few resistors.
  3. bassbenj


    Aug 11, 2009

    Don't know about your preamp, but my Fender Jazz preamp has pcb mount pots of values that would not be useable for a passive wiring.

    Personally I like the mid control as a way to get tones that you can't get from a passive or two band setup, but that is your choice.

    Note that the Z-mode thing is really designed to be used with jazz pickups and P-bass pickups have considerably different resistance and inductance. What that means is that the Z mode may not give you the tones you expect. As Line6man says, it is easy to try some different value loading resistors and see what you think.
  4. bray101


    Feb 26, 2012
    Resurrecting this...

    I am snagging one of these, but it is the active version. I really want to have the passive option.

    Has anyone had any success putting in a passive-active switch like they have in the new American Deluxe stuff?
  5. fhm555

    fhm555 So FOS my eyes are brown Supporting Member

    Feb 16, 2011
    If I'm not mistaken the new Deluxe Jazz has an active/passive toggle. If not you will need a stacked pot to replace the single pot on the pre PCB.

    You can also get an active/passive option in the MIM Reggie Hamilton P/J. It is essentially the same control package as the American Deluxe but is used to control a p/j set instead of the noiseless j set used in the American Deluxe.

    I was going to convert a full time active MIM deluxe to a/p and gathered the required parts but balked when it came time to replace the pot on the PCB, it just looked to be too easy to screw up so I passed and left it full time active.

    For some odd reason I could never fins the current MIA Deluxe/Reggie Hamilton PCB which allows for the use of an a/p switch. I never contacted Fender direct, but I scoured all the usual places and a lot of the not usual places when I was trying to find one. You can find the stacked pot needed to convert a full time active to a/p, but I had zero luck finding a PCB with the pot already mounted.

    I've still got the pot and a couple of full time active PCB's as well as a couple sets of the other pots required to make up the Fender active control group One is used but working and the other is brand new, but not working. It came to me this way and I was so discouraged by the whole thing by then I just threw it all in a box and stuck it in a closet in my shop.

    If you want the A/P option on a Fender active bass not equipped that way from the factory, you would be money (and frustration, time, etc) ahead to just buy an aftermarket 3 knob pre and swap out the fender unit for the 3 knob and use the 4th hole in your plate for the A/P switch. You can also find Fender American Deluxe pre complete replacement assemblies, including the MIA J pups on ebay but last I looked they were pushing $300. Had I not already had several sets of pups I may have tried to snag one of the complete sets off ebay, but I wound up with a Bart pre with an A/P switch instead.
  6. bray101


    Feb 26, 2012
    Very thorough reply, and it is much appreciated. Essentially, all I want to do it add the switch for passive/active to the existing set.

    I'll look up the Reggie Hamilton wiring schematic.
  7. fhm555

    fhm555 So FOS my eyes are brown Supporting Member

    Feb 16, 2011
    That was my intention when I first started, but it didn't take long to find out it was not going to be as simple as just putting in a toggle and wiring it up.

    Look up the Reggie Hamilton schematic and the MIM Deluxe Jazz and compare the parts in the preamp and you will see what I'm talking about regards the different pots hard mounted to the PCB. I'm also pretty sure the pre in the Deluxe P is the same as is used in the MIM Deluxe j basses.
  8. bray101


    Feb 26, 2012
    I have a call in with my local tech who is going to crunch the schematics tomorrow and let me know what he can do.

    I'll update when I hear from him.
  9. fhm555

    fhm555 So FOS my eyes are brown Supporting Member

    Feb 16, 2011
    Sounds good. I would love it if someone who knew what the heck they were looking at could figure a way to just install and wire up an a/p toggle for the full time active Fender preamp.

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