Feedback problem (DD Detonator) on bass

KnightOfNeon

New member
Hey everyone.

So, cutting right to the chase. I've installed a duncan designed detonator (awesome pickups, by the way) in my jazz bass. Yeah yeah, unorthodox but surprisingly, sounds awesome. The problem is, I have a terrible feedback/whale song problem. Touching the strings does not stop it and moving around changes little to nothing, bass keeps squealing (not a high pitched squeal, mind you but... well, feedback!).
The gain I was using wasn't too much and it was the bass amp gain, so no "real" distortion there. Volume was quite high, however, since I have to compete with two loud guitarists so turning down is definitely not an option!

The pickup's also hidden underneath the pickguard. I should note that I'd put a ceramic bar magnet on top of the pickup so as to "expand" the magnetic field and it does do the trick, but it also introduces a whole lot more feedback when on there. When I removed it, the feedback went considerably down (still there though) but down also went the better response it gave the pickup so I'd really like it to remain there, if at all possible.

Now, at first, I had terrible noise when I first installed the pickup, and I discovered that, that was because the poles were touching the shielding underneath the pickguard. A piece of paper between them put an end to that easily enough. Also, I shielded the humbucker's cavity but that seemed to really piss off the detonator and also introduced A LOT more noise. So, out that went as well.

Not to toot my own horn but wiring and grounding is not an issue. The wiring on the bass goes as follows. The two J pickups that were originally on the bass are hardwired in series (acting as a unit). A 500k vol. pot for the twin J's and a 500k vol. pot for the detonator. No switch, wired in parallel, just like on a standard jazz bass. There's a DPDT switch to go from parallel to series, so all three work together (with a massive reading of 19.6k, by the way!). No tone pot. Again, the wiring's not the problem. I checked, checked with a multimeter, double, triple and quadruple checked, soldered and desoldered and resoldered to test, everything works as it should. And in any case, it's only the detonator that's screaming, when turned off (or significantly down, I have an audio taper pot for it for exactly that reason) the twin J's are quiet.

At my place, playing through the usb interface and vst, bass is dead quiet. No feedback. So I'm assuming it's the volume that causes it. I'm not quite sure if the pickup's microphonic. Shouldn't be but it may have become microphonic in the years I've had it stored and unused. It originally was on a 2000something Jackson KE3. I do remember, however, having feedback/squealing issues with that guitar too, back then, with the same pickups. So, perhaps, the nature of the beast...? Hopefully not.

Anyway, sorry for the long-winded post, I wanted to give as much info as I could, so as to find a solution (if possible) faster.

Any ideas?

Many thanks in advance!
 
Re: Feedback problem (DD Detonator) on bass

You are absolutely convinced that your wiring is all correct (and I assume you're also sure there are no cold solder joints) because you say..."Not to toot my own horn but wiring and grounding is not an issue"..."I checked, checked with a multimeter, double, triple and quadruple checked, soldered and desoldered and resoldered to test, everything works as it should".

So if your wiring is correct and "everything works as it should", there is no problem and you're good to go, right?

But then you say..."Also, I shielded the humbucker's cavity but that seemed to really piss off the detonator and also introduced A LOT more noise", which tells me that there IS a problem with your wiring because shielding the pup cavity will not do that unless your wiring is incorrect and you have reversed your hot and ground wires.

You make some other interesting statements..."but it may have become microphonic in the years I've had it stored and unused". Pickups don't magically become microphonic from non-use. Otherwise every pup you buy that has been sitting on a shelf at the retailer's store and at the warehouse would be microphonic.

You..."have an audio taper pot for (the Detonantor) for exactly THAT reason" (to prevent the screaming)?!?

Normally I'd ask you to take and post some clear photos of your wiring and all the connections to help us diagnose what's wrong, but I don't think you would understand what we want. So my suggestion is that you take your instrument to a competent luthier and have him check out and fix your instrument.
 
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Re: Feedback problem (DD Detonator) on bass

You are absolutely convinced that your wiring is all correct (and I assume you're also sure there are no cold solder joints) because you say..."Not to toot my own horn but wiring and grounding is not an issue"..."I checked, checked with a multimeter, double, triple and quadruple checked, soldered and desoldered and resoldered to test, everything works as it should".

So if your wiring is correct and "everything works as it should", there is no problem and you're good to go, right?

But then you say..."Also, I shielded the humbucker's cavity but that seemed to really piss off the detonator and also introduced A LOT more noise", which tells me that there IS a problem with your wiring because shielding the pup cavity will not do that unless your wiring is incorrect and you have reversed your hot and ground wires.

You make some other interesting statements..."but it may have become microphonic in the years I've had it stored and unused". Pickups don't magically become microphonic from non-use. Otherwise every pup you buy that has been sitting on a shelf at the retailer's store and at the warehouse would be microphonic.

You..."have an audio taper pot for (the Detonantor) for exactly THAT reason" (to prevent the screaming)?!

Normally I'd ask you to take and post some clear photos of your wiring and all the connections to help us diagnose what's wrong, but I don't think you would understand what we want. So my suggestion is that you take your instrument to a competent luthier and have him check out and fix your instrument.

The wiring is correct and I am indeed certain of it. I tried the humbucker on other guitars as well, shielded and non shielded, same behaviour when volume levels rise. So I'm assuming the wiring's not at fault here.

The humbucker cavity shielding made contact with the humbucker's baseplate (the "ears" were cut off) and introduced noise. Foam under the pickup did not help anyway. Removing the shielding, however, did. Same happened when installed on other shielded guitars. I admit, I don't understand why. Other pickups worked just fine.

Pickups do not "magically" become microphonic, true. There have been cases, however, that re-potting squealing pickups does work. Reasoning behind this is, the potting could have become "loose"(?). I don't know but I would assume this could potentially be one of those cases and worth a mention, although I'd like to start somewhere else first.

I chose an audio taper pot because I wanted more of a switch rather than a linear potentiometer and I had one available. So, the audio taper's range suits my needs fine. It had nothing to do with the "screaming", considering it was wired before I could actually test the bass in that configuration and especially in louder volumes.

I'm by no means an expert but I don't understand why your reply is so condescending, not to mention marginally offensive ("...I don't think you would understand what we want"), needlessly so. I don't think I offended you or anyone else with my post here. Guess I was wrong. In any case, have a nice day.
 
Re: Feedback problem (DD Detonator) on bass

Actually, it is ideal (if everything is wired correctly) if the cavity shielding contacts the baseplate.

Potting doesn't become loose. It is wax that has been melted throughout the winding wires inside the pup. But you could try re-potting it. There are many posts here and online that give instructions.

Audio vs linear taper only affects the rate of signal reduction as the knob is rotated. There is nothing similar to a "switch" affect. It is called "audio" because it sounds more linear to human ears. The term "linear" refers to the electrical affect.

I didn't mean to be condescending, I just thought that you would get better results from taking it to someone who could actually see and test what is happening. Didn't mean to offend you. From your statements about your wiring being correct, it sounded like you wouldn't be very open to our analyzing and correcting your wiring.

Sorry to have offended you. I just want you to get the help that you need without wasting too much time.

However, if you'd like to post some pics, we'll be glad to take a look and see what we can do to help.
 
Re: Feedback problem (DD Detonator) on bass

No, on the contrary, I'm WIDE open to suggestions, corrections, solutions, advice, anything. Once again, I'm by no means an expert or pretending to be one. I'm just saying I tried swapping wires, soldering and resoldering again and again and again (this can be seen in the mess of solder in the photos below!), I've tried it on other guitars and I'm pretty certain it's not the wiring that's at fault, considering the pickup had the same behaviour in other instruments as well. If it is, I'll swallow my own words no problem.

Here are the pics, I know it's a mess but my soldering iron's pretty much the size of a hammer and that's the best I can do at the moment. Hope everything's discernible, it's a real tight squeeze in that cavity.

jbwir1.jpg


jbwir2.jpg


The black cloth wire is the twin J's ground, the white cloth wire is their hot. The one's that's going to the leftmost pot's middle lug is the detonator's hot and the one's that's going to the lower middle lug on the DPDT is the detonator's bare and ground (originally braided together, DD's have the green as hot and black as ground). The DPDT is a center-off 3way.

Thanks again.
 
Re: Feedback problem (DD Detonator) on bass

I don't see the green wire from the Detonator. Where is it attached?
 
Re: Feedback problem (DD Detonator) on bass

I also can't see what wire is attached to the middle or the third lugs of the left vol pot.

Too many wires that are red+black. Please identify them.
 
Re: Feedback problem (DD Detonator) on bass

Left pot's middle is the detonator's hot (green) and the one's that's going to the lower middle lug on the DPDT is the detonator's bare and ground. I used what I had (the red/black wires) for "extensions" and other connections.
Lower lug is (looking at the lugs vertically, as they are in the pictures) is a wire that goes to the other pot's lower lug and from there to the jack's hot. Uppermost lug (left pot) is ground (to its casing) that goes to the uppermost lug on the right pot. This one's not grounded with the rest on the right pot and doesn't go to input's ground. Should it?


edit: it wasn't that. I connected that right pot's left to the common jack ground and no change. But, I did discover that pickup's indeed microphonic (I know it sounds silly but I never thought to actually *speak* on the pickup to find out...). So I'm guess it's probably the pickup's fault. I'll try another humbucker I've got lying around and see if anything changes.
 
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Re: Feedback problem (DD Detonator) on bass

Disconnect the Detonator's bare and black (ground) wires from each other. The bare wire has to go directly to a constant ground connection (back of pot). The Detonator's black wire goes to the bottom middle lug on the switch BY ITSELF...no other wires with it. When you're doing a series/parallel switch, you can't have the bare wire (pick up baseplate ground) involved or you will be introducing that ground into the hot/lead when in series. In series you only want to connect the output of one pup (the Jazz Bass pup in this case) to the input of the other pup (black wire of the Detonator in this case). So, if you try disconnecting the bare wire from the black wire and the switch, and only have it attach to the back of a pot, you should be fine.

Both of the third lugs of the vol pots are connected together by the red and black wire and to the back of their respective pots? (At least the third lug on the right pot needs to be connected to the back of that pot).

I assume that when you are in series only the Detonator's vol (left pot) is active. Correct?

Try it after the change I recommended and get back to us and let us know how it worked out.
 
Re: Feedback problem (DD Detonator) on bass

Thanks for the help, Doc, aprreciate it immensely. I did not know that, I assumed, since they were originally braided and soldered together, they should be... one! In any case, seeing as the pickup turned out to be microphonic and I was pretty sure that wouldn't help much, I swapped it out for another humbucker I had laying around. I dimed everything trying to make it squeal but it seems quiet, so far. I'm going to save my hurrahs for after I'll have had the chance to try it in the studio but for now, it seems the pickup was the problem.

Once again, many thanks for taking the time. Much appreciated.
 
Re: Feedback problem (DD Detonator) on bass

On the pup you just put in, do you still have the ground and bare wire connected?
 
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