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Distortion after swapping out to EMG BQC System

Discussion in 'Pickups & Electronics [BG]' started by lokikallas, Apr 14, 2011.


  1. lokikallas

    lokikallas Supporting Member

    Aug 15, 2010
    los angeles
    So I went ahead and replaced the old pots in my bass, a pair of 25K vols, a tone, and a blend pot with the BQC system from EMG. I have a set of 90's EMG P-J pups in the bass. I have everything wired up, added a 2nd 9v in series, and plugged it in. Everything works as far as bass, treble, mid, blend and vol, but with an overdriven signal. I noticed that the BQC system vol was a 50k, but my understanding is that is fine for actives.
    The old set up worked, but the blend was funky, and I wanted to expand my tone controls. The tone control was previously just a 25k pot with a capacitor to roll of highs. Any ideas why I might be overdriving now? I'm fairly competent at soldering, so I don't think I fried anything, and I even tried soldering back in one of the 25k pots for volume instead of the 50k that the BQC uses. The BQC system comes all wired together to basically just solder the pup's to, the battery, and input jack.
     
  2. walterw

    walterw Supportive Fender Commercial User

    Feb 20, 2009
    alpha-music.com
    look for a simple, goofy error, like having the wires wrong on the output jack, or a 1/4" plug that won't fit all the way in.

    otherwise, it's rare, but possible, that you just have a bad preamp card.
     
  3. FunkMetalBass

    FunkMetalBass

    Aug 5, 2005
    Phoenix, Arizona 85029
    Endorsing Artist: J.C. Basses
    Is it the bass or the amp that's causing the overdriven sound?
     
  4. lokikallas

    lokikallas Supporting Member

    Aug 15, 2010
    los angeles
    It's definitely the bass. The gain from the amp can be very low, and still overdrive. The output of the bass volume starts to distort around the 50% mark and gets worse as you reach wide open. The bqc system is mostly prewired. All you have to solder is the battery clip, the pups to the input card, and the 1/4" jack. I hope it's as simple as a bad OOTB card. I'm calling EMG support today.
     
  5. lokikallas

    lokikallas Supporting Member

    Aug 15, 2010
    los angeles
    EMG tech suggested I try lowering the pickups... I'll try this tonight, but I'm a little skeptical. I'll take some pics to email him too, maybe try to post them here.
     
  6. FunkMetalBass

    FunkMetalBass

    Aug 5, 2005
    Phoenix, Arizona 85029
    Endorsing Artist: J.C. Basses
    His thought is the same as mine - your pickups are too hot and they are over driving the opamp in the preamp.

    If your volume control is before the preamp in the chain, you might be able to try a 25k pot.
     
  7. walterw

    walterw Supportive Fender Commercial User

    Feb 20, 2009
    alpha-music.com
    that's bogus.

    EMG J pickups are not gonna turn an EMG preamp into a fuzzbox. neither is a 50k volume pot. there's something actually wrong with the circuit.
     
  8. Chrisk-K

    Chrisk-K

    Jan 20, 2010
    AZ, USA
    I don't think the EMG tech is correct. The BQC system works only with EMG pickups and the EMG PJ pickups are not hot at all compared with some other EMG pickups. Perhaps, the preamp board is damaged.
     
  9. THand

    THand

    Jun 9, 2008
    Agreed. I have the same set-up on one of my basses and it doesn't do this no matter how close the pups are.

    Get a replacement.
     
  10. lokikallas

    lokikallas Supporting Member

    Aug 15, 2010
    los angeles
    Yeah, I most likely will end up sending em back. What a pain in the ass. I tried the 25k volume pot that I had in the bass before the swap. No difference. The pickups go to an emg blend before going to the volume, then the eq board, then the output jack with the bqc system. I would guess there's something up with the eq board.
     
  11. lokikallas

    lokikallas Supporting Member

    Aug 15, 2010
    los angeles
    Problem solved! So, I took the electronics out of the cavity to give it a once over and take some pics, and for kicks, I Plugged it in again. It sounded fine. So I started putting stuff back in to see what the problem was. As I put in the EQ circuit board, I heard crackling. I checked it out and sure enough, when the circuit board made a little contact with the inside walls of the cavity, the sound would be effected. If I pressed on it just right, and certain contact points on the back side of the board were touching the wood, then it would work, but with distortion. A little bit of E tape later and I'm all set. I always thought that wood wasn't conductive unless wet, but I guess it is conductive enough to effect the electronics.
    The problem is, the bass is an old Alvarez Dana "Offset Fretless Four String". Cool little cheap bass, but the offset also means very small electronics cavity. I barely fit the BQC circuits in, let alone the 2nd 9volt in. The cover plate basically holds the 2nd battery in place.
    I appreciate the feedback. I am enjoying the BQC, it isn't the be all, end all, but it certainly opens up the bass over all. The new blend is really nice, and I think I like a mix of 60% bridge J and 40% neck P. The bass and treble will most likely stay at 0 for the most part, but I will play with the mid to add or cut just a bit.
     
  12. stflbn

    stflbn

    May 10, 2007
    Nashville
    I've just encountered the same issue with a new BQC system (with dual EMG 40DC's). All signal is completely distorted, and any time the volume knob is raised to 100% or lowered to 0% the signal pops and cuts out for a couple seconds then comes back on. Does it with the unit in the bass, or in my lap. Traced the wires according the the diagrams and one section was actually connected wrong from the factory, though changing it to how it is on the diagram and on the circuit boards doesn't fix this issue. Not to mention the new shrinkwrapped and uncut seal on box system was missing Nuts for the two larger Diameter Stacked pots (I happened to have 2 the right size)

    I've self-installed and soldered at least 4-5 OBP-3's, Glockenklangs, John Easts, etc with no problems, so I don't question my ability to follow a "plug this in here type diagram". I went with this BQC system because I needed a very quick solution and expected it to be brainless.

    So I'm also thinking there's something amiss somewhere...
     
  13. walterw

    walterw Supportive Fender Commercial User

    Feb 20, 2009
    alpha-music.com
    like i said, something simple and goofy.
    it's not the wood, it's (i'll bet you a quarter) the black paint inside the cavity, which is actually conductive graphite shielding paint.
     
  14. stflbn

    stflbn

    May 10, 2007
    Nashville
    My spector has shielding paint also, but this BQC system was doing the same exact thing when removed from the bass, only worse. The volume pot and connections themselves were noisy and cutting in and out.
     
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