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Thread: Active EMGs, passive wiring, need help w/values and wiring

  1. #1
    Senior Member Stealth's Avatar
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    Active EMGs, passive wiring, need help w/values and wiring

    (This is a repost from TB as I don't think enough light was shed on the idea back there)

    Alright, the Hohner B2A I bought second-hand a few weeks back proved its worth as far as the tone's concerned - the EMB-HBs really have a monstrous sound. Now it's time to fix the wiring inside for a few reasons:

    • The wiring is poorly marked - five out of ten wires are yellow, and the yellow doesn't always designate the ground.
    • The pickups are active, thus necessitating a stereo jack.
    • The old stereo jack was crackling because it didn't grip the output cable firmly enough - the cable would pop out under its own weight.
    • I want to exchange the old three-way switch (neck/series/bridge) with a two-way (series/parallel) complete with the "individual series volumes" mod, pickup loading be damned.
    • The red LED has to go - I want a green one.


    Since the bass sounds good as it is, I want to keep as much of the original electronics specs as possible.
    • The two vol pots are 25K, linear taper - easy to source, makes sense since it's standard value for active pickups.
    • The DPDT on-on won't be a bother, and neither will the LED.
    • I've already found a decent stereo replacement jack with a chassis mount, as that's the type that fit inside the electronics cavity.


    However - the tone pot is a 25K audio pot with an unknown capacitor on it. I haven't a multimeter to test it with, so I have no idea what it is aside from a mysterious label 1K10 (which would suggest a 1100nF, or a 1.1 uF capacitor). I haven't seen any 25K audio pots around, and the 1.1 uF caps are also confusing as they're usually either 1.0 uF or 1.2 uF, at least according to most shops.

    So, my questions are as follows:
    • Are 1.1 uF caps really available or should I default to 1 uF?
    • Could I simply mod a 25K lin pot with an extra resistor to provide the log taper?
    • Can someone shed a light on the proper wiring? Or, rather, the proper tone pot and cap values for an active pickup configuration?
    • For that matter, can EMGs even be used in series/parallel switching mode? From what I recall the pickup leads are signal +, signal ground, Vcc, -Vcc, shielding GND, so should there really be any issues with an S/P configuration?


    Edit: To clarify on the S/P, this is what I had in mind - snagged the schematic from somewhere at TB.
    Last edited by Stealth; 05-01-2010 at 05:48 PM.
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  2. #2
    Pickup Maker David Schwab's Avatar
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    You cannot wire active EMGs in series.

    The tone cap is .1F.
    It would be possible to describe everything scientifically, but it would make no sense; it would be without meaning, as if you described a Beethoven symphony as a variation of wave pressure. Albert Einstein

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  3. #3
    Senior Member Stealth's Avatar
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    Hmm. That would mean something's gone awfully wrong with the original wiring. Or there's witchcraft involved.

    Unfortunately, I don't have a photo shot of the wiring - doubt it would be of any use as it's really a mess of wires. What you said about active EMGs not being able to work in series really confuses me for the following reason:

    • When the pickup selector switch is in the neck position, volume knob 1 controls its volume, volume knob 2 has no effect. Tone works normally.
    • When the pickup selector switch is in the bridge position, volume knob 1 has no effect, volume knob 2 controls its volume. Tone works normally.
    • However, when the selector is dead center, both volume knob 1 and volume knob 2 control the volume, and either can be used to completely fade the volume to nil.


    Isn't that how a series wiring is supposed to work?

    Thanks for the cap value. Now it makes more sense.
    Last edited by Stealth; 05-03-2010 at 09:30 PM.
    Pickup prototype checklist: [x] FR4 [x] Cu AWG 42 [x] Neo magnets [x] Willpower [ ] Time - Winding suspended due to exams.

    Quote Originally Posted by David Schwab
    Then you have neos... which is a fuzzy bunny wrapped in barbed wire.

  4. #4
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    Quote Originally Posted by Stealth View Post
    Isn't that how a series wiring is supposed to work?
    They do not not need to be connected in series for that to happen.

    If the pots are connected with the slider going to the output (the normal way, rather than from the pickup), then when both pickups are switched on, the two sliders are connected together and turning down one pot grounds both sliders and you get nothing from either pickup.

  5. #5
    Pickup Maker David Schwab's Avatar
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    Each pickup has it's own volume control, and then they go to the switch. The output of the switch goes to the output jack. So when you select that pickup, you have switched the other volume control out of the circuit.

    That's how every guitar with a pickup selector switch and two volume controls works.

    http://www.emginc.com/content/wiring...0230-0014a.pdf

    3-way Switch Wiring Diagram
    It would be possible to describe everything scientifically, but it would make no sense; it would be without meaning, as if you described a Beethoven symphony as a variation of wave pressure. Albert Einstein

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  6. #6
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    Maybe these works.
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