Insertion Loss?

Discussion in 'Pickups & Electronics [BG]' started by R. Laevinus, Jul 29, 2009.

  1. EMG claims there's a thing called 'insertion loss' or somesuch, which means that when two signals of similar amplitude are mixed, an overall drop in amplitude occurs. I think they're just trying to sell me a new blend pot, but nonetheless, I HAVE a fairly major problem on one of my basses.

    The bass is a Traben, and I've converted her to passive (no disrespect to all you active types, but I can't stand that stuff), and when I switch both pickups on at once (via a Gibson-style 3-position toggle) - the output, and tone, drops to basically nothing.

    She's mounting a Rockfield J and MM, and I have no idea what's going on or how to fix it. Both pickups are humbuckers, both are still wired in their factory config. I've tried coil-tapping the MM, but that didn't help at all. The only other controls (that matter) are a master volume and a master tone.

    The only thing I've found that might help is the Villex booster, but it seems too good to be true:

    From the Villex Website -
    "Gain equalization for multiple pickups

    Villex boosters automatically raise gain levels for two pickup selector positions, such as positions 2 and 4 on a Stratocaster, to make them level with one pickup selector positions. This improves the sound of the positions 2 and 4, making them sound as loud as positions 1, 3 and 5. Since positions 2 and 4 have humbucking properties, they can be used in a high electromagnetic hum environment."

    I have no idea how this could be possible, and I'm fairly good with electronics, but there it is.

    If you've experienced this, let me know how you dealt with it - or even if you haven't, let me know how you would! Solutions that don't involve buying things are preferred, but I'll do what I have to do.

  2. TrooperFarva


    Nov 25, 2004
    New City, NY
    Your pickups might be out of phase
  3. StephenR


    May 21, 2009
    SF Bay Area
    If the bass is wired properly there should be no need for an external booster in order to use both pickups simultaneously. The volume drop shouldn't be that severe. From the description it sounds like your pickups may be out-of-phase. Have you tried reversing the polarity on one pickup?

    must learn to type quicker... what he said above!
  4. I have not tried that, no. How would I go about it? Excuse me a moment while I search the forums...
  5. Angus

    Angus Supporting Member

    Apr 16, 2000
    Palo Alto, CA
    Swap the hot/gnd on one pickup.
  6. It's that simple?

    Just switch out the red for the black?

    Okay, I''l try that tonight and let you guys know how it goes.

    By the way, thanks for making TB such a great spot... my questions answered in under 60 minutes. Amazing.
  7. bongomania

    bongomania Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    For a somewhat contrary view ;), "insertion loss" is very very real and well documented. However if your pickups are correctly wired (phase, grounding, etc.) the drop in level when two pups are passively blended equally should not be all that bad. Noticeable, real, but not significant.

    The Villex boost works by robbing energy from one frequency range, and using that energy to boost another range.
  8. Thanks for the info, Bongo! That's very interesting, and potentially very useful... I'll file that away in my head.

    As for the Villex, though - it's a mid-boost, right? So which frequency does it steal from, do you know?
  9. bongomania

    bongomania Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    I think (speculation only) that it takes from the highs, and exaggerates the resonant peak at the corner frequency where the highs begin to roll off.
  10. SGD Lutherie

    SGD Lutherie Inactive Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    Insertion loss is different from impedance loading, which is what's going on when you mix two pickups.

    Insertion loss is when you send you signal to a passive tone stack (bass/treble controls), and there is usually a gain recovery state to make up for that loss.

    If the output drops to almost nothing, with very little low end when two pickups are mixed, they are out-of-phase with each other. As others have said, just reverse the polarity of one of the pickups.

    What I think Villex is doing is using transformer type circuits to achieve a resonant boost system. You can get small boosts from a passive system, and that's exactly what happens when you turn a passive treble cut tone control all the way off.
  11. SGD Lutherie

    SGD Lutherie Inactive Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    I agree. I also think he uses transformers to boost the level of lower impedance coils. I base that idea on the fact that he invented the Lace Transsensor and Alumitone pickups, and that's how they work.
  12. That's VERY interesting - I've been wondering about the Alumitones. Thanks!
  13. Yep...the pickup is primarily and inductor (L)...and the tone control rolled completely off is essentially a capacitor (C)...when you combine an inductor and a capacitor in this way, you get an LC resonant circuit. If you knew the effective inductance of your pickup(s) and the value of your tone capacitor, you can pretty accurately calculate the frequency of your resonant peak. Fr = 1 / (2 pi L C)
  14. SGD Lutherie

    SGD Lutherie Inactive Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    Alumitones, and the Transsensors, both use a single loop coil. The Transsesnsors used a copper loop. This becomes a very low impedance coil, but with higher current.

    Then they have built in stepup transformers to get the level and impedance to match high impedance amps.

    If you want to look up the patents, they are 5767431 and 5831196. It's a really clever design.

    People forget about the Transsensors because they look very "normal" compared to the Alumitones, but they sound very good.

    Attached Files:

  15. Stealth


    Feb 5, 2008
    Zagreb, Croatia
    So in other words, Lace Sensors are low-noise, low-impedance and low voltage coils but generate a high current so the transformer can then bring the voltage up to nominal value?
  16. SGD Lutherie

    SGD Lutherie Inactive Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    Not Lace Sensors, just the Lace Alumitone and Transsensor pickups.

    The Lace Sensors are high impedance pickups.
  17. Stealth


    Feb 5, 2008
    Zagreb, Croatia
    My bad, misread it. :oops: Thanks for clearing it up, really interesting stuff.
  18. Fascinating... thanks for the info! Now I'm GASsing for a set for my six-string.

    But anyway, I flipped the phase of my bridge pup last night, and now she sounds just fine. Thanks!
  19. jesterbass


    Apr 20, 2007
    So, thread necromancy.

    I'm about to wire up my Ibanez SR605 with a pair of Nordstrand Dual Coils. I have two options for blending, an ungrounded MN500K blend pot, but I also have an EMG ABC active blend. It would be nice to keep the bass all passive and not requiring a battery (for the active control), but then again this insertion loss thing... I would like to maintain all my top end intact. If I use the ABC control I will also be able to use two individual passive tone controls between each pickup and the ABC blend's buffers. I was thinking of what to do with the available holes after removing the preamp and thought of that possibility, not sure how much fun dual tone will be in practice. What would you guys do, passive blend or active blend against insertion loss?
    Last edited: May 21, 2019
  20. ex-tension


    Jun 11, 2009
    I would try both options and keep what I like.