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Anybody Work with Dummies?

Discussion in 'Pickups & Electronics [BG]' started by bassbenj, Jan 14, 2012.

  1. bassbenj


    Aug 11, 2009
    I'm sick and tired of single coil hum! Yeah, running my JAZZ SX basses with both pickups full on is great, but I'm wanting to actually USE mixed variations of the two pickups.

    Since we are talking SX basses here I'm not about to spring for a bunch of Nordies for them to fix the hum. So what to do?

    Well, In an Alembic thread there were quotes from Mica talking about dummy coils used in Alembics to solve the problem! That got me thinking.

    What about simply adding a dummy coil to the SXs? I can easily rout a place under the pickguard for it without worry about ruining looks. So I began to experiment. It's a bit tricky, if you haven't tried this because of the reverse wind between the two pickups that makes them humbuckers when both are on full. This means that the dummy coil has to be out of the circuit when both pickups are on and be in the circuit when you have neck or bridge dimed. And even worse, the dummy must reverse phase as you switch from neck to bridge. Not so simple!

    Well eventually I came up with wiring the coil between the two sliders on the vol/vol pots. This seems to almost do the job. To try it out (since I don't have a true dummy coil yet) I simply took an old jazz pickup to use as a dummy (keeping it away from the strings for now). Works great EXCEPT that the added parallel inductance (dummy is added in parallel) really kills the volume of the bridge pickup a lot. But the hum is definitely under control!

    further experimenting showed that if I could somehow use a SERIES connection for the dummy it would work much better. But I can't figure out how to wire one series dummy coil for two pickups!

    Does anyone have a wiring diagram for a single dummy coil with two pickups that is a series connection? Anyone have an alembic wiring diagram that might give me a hint. I'm SO close to this working now!

  2. Mike M.

    Mike M.

    Feb 14, 2010
    I've never tried a dummy coil. But as a thought, have you thought about a good proper shielding of the pickup and control cavities?

    I bought a Squire VM fretless Jazz bass and wow, did that thing ever hum when ever I turned either one of the pickups down. Hell, it was worse when I turned both pickups all the way down!! Took it to the tech I go to, he shielded it and now it's nice and quite.

    I have another Jazz bass that has Seymour Duncan Antiquity II pickups in it. While I was waiting for the pickups to arrive I read how some folks said they had them, then took them out due to the noise. When the pickups arrived I told the tech to give it a good shielding before installing the pickups. I have never had any problems with noise with that bass.

    Some will say that it won't get rid of all noise due to lights or whatever else. Sorry, don't know what to tell you but I haven't had any issues with my basses shielded.

    Just a thought.
  3. SGD Lutherie

    SGD Lutherie Banned Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    OK, so since you started the post with Alembic, note that their system is active. They use a single dummy coil and actively sum that with the other two single coils. It works with both pickups because they are the same polarity, and it's active.

    That's for the series I and II basses.

    Now if you want a series dummy coil to work with both pickups, you need one for each. Then you end up with what Alembic does for their newer AXY pickups, they are stacks. Stacks tens to have low output, but of course in the case of Alembic, once again they are active basses. Alembic has the bottom dummy coil wired in series with the top coil.

    Another actively summed stack is the EMG J.

    Now if you want to try it passive with one coil, you would need the two pickups to be the same polarity, and not set up to hum cancel. So the magnets in both pickups have to be the same. Does the SX use ceramic magnets under the pickup like they do on their guitar single coils? If they do, it's a simple matter of prying off the magnet (be careful to to break it) and flipping it over.

    Then you would connect the ground sides of both pickups together, and then through the dummy coil with the other end of the dummy to ground. I haven't tried this, but it should work.

    The big problem with dummy coils is the affect on the tone of the pickup.
  4. bassbenj


    Aug 11, 2009
    You are right! I completely forgot about Alembic dummy coils being added in actively! I really do want to try to keep the SX basses passive and simple!

    And yes, SX pickups do have the ceramic magnet underneath and I love your idea of using two pickups of the SAME polarity rather than the usual cancelling ones. There certainly might be some progress hiding in that idea! I was thinking strictly in terms of the existing polarities up to now and that causes the coil to need to be reversed when you go from one pickup to the other.

    And yes the big problem is change in tone. And I really don't want to do the stacked coil thing because my Fender has that and the tone leaves a LOT to be desired! Side by side pickups are great but expensive and I really am looking for something cheap here (like a coil of wire I can make myself). Of course I can make two coils of wire but that is just the stacked coil option even if I don't stack them!

    But so far my experiments showed that a coil in parallel or in series with the neck pickup sounds pretty good! But the coil in parallel with the bridge pickup really shunts signal to ground. The coil in series, on the other hand doesn't sound half bad even though it still blocks some signal and highs.

    Anyway, my original idea was to leave my two pickups series and parallel as is (which naturally buck hum) and then switch in a dummy coil for neck-only and bridge-only settings (most of my SX basses are wired with a neck,series, parallel, bridge rotary selector switch). It seems like with enough switch poles I ought to be able to come up with SOME way to do this with a single coil and not worry about any blending thing.

    But it's a pretty complicated deal! But thanks for some more ideas! TB always seems to come through! Putting thinking cap back on!

    Thanks David!
  5. SGD Lutherie

    SGD Lutherie Banned Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products

    Technically that's what you are doing! Only without the lower frequency phase cancelation.

    EMG Selects are pretty cheap, and they don't sound bad either. They are split humbuckers.

    Some of the newer stacks are sounding pretty good, at least on guitar. The DiMarzio Virtual Vintage series really sound like single coils. I guess it doesn't work as well on bass since they haven't gone in that direction. Interestingly, Fender just released the "Super 55" split coil pickups for Strats and Telles. So I guess that method is gaining traction.
  6. SGD Lutherie

    SGD Lutherie Banned Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    Single coils pick up two kinds of interference. One is 60/120 Hz hum. That's magnetic field noise. The second is the high pitched electrostatic noise, the kind that goes away when you touch the strings. That's electrical field noise.

    Shielding only helps with electrical field noise. To get rid of hum, you either need a hum canceling pickup of some kind, or something like what Lace does with their Sensors. They have a sort of magnetic shield around the pickup.
  7. cnltb


    May 28, 2005
    Sorry - it has been aluded to earlier...some stacked humbuckers don't sound so good it seems...

    What was the reason for that again?:)
  8. I have a custom J bass with older DiMarzio stacked hum buckers that sound awesome,check into them.
  9. SGD Lutherie

    SGD Lutherie Banned Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    I don't think DiMarzio ever made stacks. They have all been split coil inline humbuckers with a coil under each pair of strings.
  10. Avalon


    Feb 28, 2009
    Not to derail, but I was about to join a rant about my job. Nevermind. Please carry on.
  11. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    a set of dimarzio area Js sells for like $150;

    the whole dummy coil thing has been thoroughly explored, as david is alluding to.

    it's not more popular because while it works, it sucks tone, whether series or parallel. (that's why successful designs, including stacked pickups, usually specify or include preamps.)

    the more promising avenue of exploration is with the ilitch wide-coil stuff; by creating a huge coil with only a few turns of wire, significant "anti-hum" is generated at the cost of almost no added inductance, resistance, or whatever, so no tone change.

    suhr guitars has used this system for years to great success, and have just parted ways with ilitch to start using their own version, which rumor has it will be able to be installed in a control cavity easily.
  12. Meddle


    Jul 27, 2009
    I'm curious as to the viability of dummy coils since I learned about Alembic basses having them. I have a cheap Strat copy at home that I rigged with a dummy coil, so that there was only one master tone control and the second tone control dialed a dummy coil in and out of the signal. I used a strat pickup with the magnet removed.

    I think the first thing I should say is, it didn't exactly work. There is a reduction in overall hum, but I use a clean power supply anyway so I don't get a lot of hum and noise. Secondly, it shaped the EQ. Dialing in the dummy coil rolled off the treble and seemed to compress the signal. It was a flatter more 'normalised' output with a slightly different placing of the mid frequencies. Not an unpleasant tone and actually good for removing some of the personality-less icepick tone coming off the strat pickups I was using.

    My worry with replicating the effects with a bass would be a total loss of low frequency or a different shift in the EQ without predictable consequences. I understand the dummy coil has to have a similar output to the pickups you use, so perhaps my dummy coil was slightly hotter.
  13. SGD Lutherie

    SGD Lutherie Banned Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    One thing you should do is if you remove the magnets, replace them with steel rods, or even screws. Removing the magnets lowers the sensitivity of the coil to pick up hum.

    What Dimarzio, Kinman and Duncan are doing in their newer stacks is to have extra steel in the bottom coil, and less windings with slightly larger diameter wire. Then they shield the top coil from the bottom with a steel U channel.

    Another development is the Chiliachki/Suhr dummy coil system. They use a large area coil wound with larger diameter wire and less turns than the pickup. You can look this up in patent application # 20050204905. They haven't made any for basses, but it seems to work very well on guitars with single coils.

    [edit] I just saw that Walter mentioned this. Seems that Chiliachki shortened his name.

    But as with all the other methods, there is a slight change in tone.

    There really isn't a perfect way to do this with a passive system.
  14. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    "chiliachki", huh?

    i can confidently say, having played many suhr guitars with the system and having installed many of the backplate retro-fit kits, that the tonal effect is way less than any other hum-canceling method.

    lots of the suhrs come with push-pull knobs to defeat the hum-canceling coil, i guess to serve as a "demo switch" in the music store. with one in my hands, i could not tell any tonal difference that wasn't subtle enough to chalk up to placebo effect, since i knew whether it was switched in or out.

    i had a friend play one behind my back, through a clean amp and with the guitar oriented so that there was no audible hum either way, and he would switch back and forth without telling me (not double-blind, but the best we could do):

    i was barely able to tell a difference, in that there was slightly more high end without the coil engaged, but it was like hearing the difference between a good 10' cable and a good 20' cable! were it not for the immediate switching, i would have never been able to tell any difference.

    the trade-off here is that the hum-canceling is not as perfect as with a stack; with high gain, the strat singles had as much hum as a more noisy humbucker pickup.
  15. SGD Lutherie

    SGD Lutherie Banned Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    Yeah. That's like Villen Khanagov. Know who that is? I'll give you a hint, he makes very good bass pickups.

    I guess those names are hard for English speakers?

    All the demos I heard sounded very good.
  16. bassbenj


    Aug 11, 2009
    The reason for it is that you have a pickup and then you have what is essentially a second pickup without magnets. If it had magnets and was reversed it'd be a standard humbucker. But with the dummy coil, the second coil only picks up hum. Then in a passive mode you put that coil either in series or parallel with the original pickup to cancel the hum. And it does. But the problem is that you've either added inductance and resistance in series or in parallel with the original pickup which can drastically change the sound. The Active Alembic system adds in the negative hum electronically (like a mixer) so there is no change in the signal from the original pickup.

    While I am interested in some kind of system for guitar as well as bass, the current plan is to somehow get the hum out of my SX basses when singled in either neck or bridge mode.

    1. I Don't want to spend a fortune on killer split coil pickups. and since some of the SX basses are 6 strings and pickups have odd ear spacing, there are really none I could buy for those. I should also mention that my MIM Fender V has Stacked coil "Noiseless" pickups and tone leaves a bit to be desired. Dimarzios seem EXCELLENT at a great price! Too bad they decided not to make them in sizes that are direct replacements for Fenders! <sigh> (We've been through that loop here before) And let me add that I LOVE the tone of my single coil SX factory pickups and really don't want to change that.

    2. In the both pickups on full mode in series or parallel it already cancels hum fine. The question is just the two singled pickups.

    3. I've run some tests using an old 4-banger Jazz pickup as a "dummy coil" and it almost worked. Tonal change on the bridge pickup was worst.

    4. This and posts here got me to thinking about the "Large coil" idea. That lets you use fewer turns and gives lower resistance for the coil. The idea is to hide the dummy under the SX pickguard and there is lots of room under there for a bigger coil. I'd also do the same thing with my Strats. Strats are more complex because they have three pickups in various combinations and polarities.

    5. A variation of that I haven't tried is to use a larger coil with a ferrite core to reduce the number of turns still further. As David says, you can just use iron too. You don't want magnets though because you don't want it picking up the strings, only hum.

    6. Just wiring the dummy coil between the two volume sliders (center pins on pots) on a vol/vol/tone setup produced not TOO bad of results but when the bridge was singled the dummy coil impedance really seemed to load it down a lot!

    7. So I'm still trying things. I really like that "big coil" idea and I'll have to order some wire from StewMac and give one a try!

    I seem so close already, I'm SURE there has to be a sensible way to come up with a simple dummy coil wiring for a passive bass that will make the singled pickups if not hum-free at least with reduced hum.

    And I can add that all these basses have been totally copper foil shielded to remove as much electric hum as possible. They are AMAZINGLY quiet when both pickups are on full either in series or parallel. Which is why the loud hum when you single a pickup is so annoying!
  17. Suhr


    Dec 28, 2008
    No there is no real "easy" way to do it passively. It can be done though with excellent rejection across the complete bandwidth with very minimal change to the tone, far less than changing to even another single coil pickup. One way is Ilitches way and there are patent issue there. We have a new passive way that works great but due to patent application issues I can't discuss it. I've been working on it for a year with my good friend Jim Kelley who works at UCI in their lab.

    Combination of pickups unless all different outputs don't make it any more complicated. Doing it Ilitches way isn't easy either. You will spend years dialing it trying to guess at the physics.
    Lets not forget that people have been working on this issue for 30 years and recently only a few realized the answers.
    Also quite interesting is Bill Lawrence back in the 70's knew the answer and a local newspaper printed an article about it. It wasn't the only way to get there though.

    My best advise is unless you have tons of good test gear, ********* of time, a minor in physics, Hemholtz coils and complete access to wire, winding machines, fabrication etc..... Easiest solution for a bass is to build a differential opamp circuit, a matching coil to your pickups or a trimmer to adjust for difference and do not put the dummy under the strings.
    I did this before we went to side by sides at Fender for the Deluxe series. Worked great but cost $10 too much:rollno:


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