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Post subject: Jazz bass wiring buzz.
Posted: Fri Nov 27, 2009 12:09 pm
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Aspiring Musician
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Hello all,
I have 2000 MIA Jazz bass that I'm using in the studio, and when I only use one of the two pickups, there is a buzzing noise. I'm more of guitar player, so this usually means a wiring issue, correct?

TIA

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Posted: Fri Nov 27, 2009 12:37 pm
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My understanding is that this is typical for a Jazz bass. I believe The pups are wired out of phase in order to get a hum-cancelling effect, but you only get that humbucking effect when both pups are at the same volume level. In effect it is a wiring issue, but it's inherent in the design.


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Posted: Fri Nov 27, 2009 8:22 pm
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interesting, guess I'll leave that way until I find a decent mod.

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Posted: Sat Nov 28, 2009 12:00 am
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If the body cavity is properly shielded, and you get the right humbucking/noiseless pickups, you should be able to lessen if not get rid of the noise. The only thing is, from my understanding (i.e.take this with a grain of salt) such noiseless pickups usually don't have as good a tone. That of course, is likely to be a matter of opinion, depending on who you ask. Myself, unless it gets really annoying at some point, I'll probably leave my Jazz alone.

As an additional thought, interference from sources like flourescent lights and other electronic devices might exacerbate the problem, you may want to look into your environment.


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Posted: Sat Nov 28, 2009 8:05 am
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Bathead wrote:
If the body cavity is properly shielded, and you get the right humbucking/noiseless pickups, you should be able to lessen if not get rid of the noise. The only thing is, from my understanding (i.e.take this with a grain of salt) such noiseless pickups usually don't have as good a tone. That of course, is likely to be a matter of opinion, depending on who you ask. Myself, unless it gets really annoying at some point, I'll probably leave my Jazz alone.

As an additional thought, interference from sources like flourescent lights and other electronic devices might exacerbate the problem, you may want to look into your environment.


I find often noisless pickups have less midrange than their noise'd counterparts. Some people like that, but I personally like heavy midrange in my pickups.

Shielding the pickup and control cavities can greatly reduce the hum.


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Posted: Sat Nov 28, 2009 10:36 am
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The standard Jazz pickup is a single coil. All single coil pickups hum. Wiring two of them out of phase reduces the hum which is the basic Jazz Bass circuit. When soloed there is no humbucking so you get more noise. Anubis is correct, the "Noiseless" pickups don't sound as good.

Even the custom made split coil Jazz Bass pickups by the popular custom ships like Lindy Fralin, Curtis Novak, Jason Lollar, Rio Grande and others don't sound exactly like a single coil, but they do totally eliminate the hum, buzz and RFI. Neon signs drive most single coil pickups nuts and so do light dimmers.

I agree with what Bathead says about shielding helping out. It doesn't completely eliminate it but it does help and is a very cost effective upgrade since you are looking at about $10 worth of copper sheeting and tape. Doing the shielding job requires some partial disassembly of the body components, but if you can undo some screws and make three solder connections you can do this easily in a few hours. You can order copper shielding supplies from http://guitarpartsresource.com/middle_bass.htm and I think you'll find it beneficial on just about any passive bass. Since it doesn't cost much money the ONLY reason not to do a shielding job is if you have a vintage bass with collector value.

I wouldn't recommend doing a star grounding/shield job on a vintage instrument as it is considered a modification.

Helpful links about shielding, the second has good photos & directions too:
http://www.basssessions.com/oct04/shield.html
http://www.artandtechnology.com.au/guitar/shielding-strat.html
Even though a Stratocaster is pictured, the principals are the same.


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Posted: Sat Nov 28, 2009 3:47 pm
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Just wondering, Is my 2009 AmStd Jazz bass possibly shielded? I ask because I discovered that my 2009 MIM Strat is fully shielded from the factory, and I would think if the MIMs are, then so should the AmStds. All I know is so far it seems relatively quiet, but I haven't had the chance to turn it up past aparment level volumes.


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Posted: Sat Nov 28, 2009 5:14 pm
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Bathead wrote:
Just wondering, Is my 2009 AmStd Jazz bass possibly shielded? I ask because I discovered that my 2009 MIM Strat is fully shielded from the factory, and I would think if the MIMs are, then so should the AmStds. All I know is so far it seems relatively quiet, but I haven't had the chance to turn it up past aparment level volumes.


I have a 2008 AmStd and it is NOT shielded. I don't know about the 2009 models. Just take off the control plate to check, no harm will come from it.


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Posted: Sat Nov 28, 2009 5:28 pm
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I did have the pickguard off when I changed it out, I think the pup cavities might have been shielded, but I'm not sure, it was hard to tell. Maybe I'll do that and check under the plate.
As I said, I can't see Fender shielding their "economy" MIM instruments, but not their MIA ones.


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Posted: Sat Nov 28, 2009 6:33 pm
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Bathead wrote:
I did have the pickguard off when I changed it out, I think the pup cavities might have been shielded, but I'm not sure, it was hard to tell. Maybe I'll do that and check under the plate.
As I said, I can't see Fender shielding their "economy" MIM instruments, but not their MIA ones.


Could you repeat that last sentence for the hard of hearing? Just the last sentence please?

AFAIK Fender does not fully shield any pickup cavities nor control cavities on even Custom Shop stuff. It is far too labor intensive a thing. It can take 8 hours or more to fully shield a Strat. It takes about 3 to 4 hours on a P-Bass since there is only one pickup cavity. 4 to 5 hours on a Jazz. (Well worth the time too.) If it was fully shielded you would have seen the copper lining in the control cavity and the ground wires running from the shielding to the control ground.

The only thing I leave unencased by copper is the fronts of the pickups. I ground the copper lining of the pickup cavities and the control cavities to ground of the pots. I build a copper cage around everything but the front of the pickups. There is a semi conductive paint you can use too. Some Ibanez instruments have this paint, but still copper shielding works better.

You maybe are mistaking the tiny bit of aluminum foil (ungrounded) on the back of the pickguard that passes as "shielding" on Fender Strats and P-basses. That really isn't as effective as totally encasing all electronics in copper wired to ground with only exposing the fronts of the pickups naked. The ungrounded aluminum on the pickguard is roughly equivalent to using an umbrella against a nearby thermonuclear detonation. The umbrella is better than nothing but you are still gonna glow in the dark.

The aluminum foil you see on the pickguards helps about as much as peeing on a forest fire. Even the pickup baseplates on premium instruments are inadequate even when grounded because they don't protect the sides, just the back. I want to encase the entire pickup cavity and control cavity in grounded copper just as the photos show in the link in my previous post. Leaving only the front of the pickups bare is required of course. You have to ground all the shielding too which requires 2 extra ground wires on a P-Bass (one for the pickup cavity and one for the control cavity) and there are 4 extra ground wires required on most Strat shielding jobs.

If the pickguard fully surrounds the pickup cavity, you should overlap the copper over the edge of the control cavity and line the back to the pickguard with copper. Then when the pickguard is put in place the copper to copper contact shields the front of the instrument. On pickups like the bridge pickup on a Jazz, which isn't surrounded by a pickupgard, I bring the shielding up the side of the pickup cavity to near the top of the pickup. If a little shows tough.

Once done, check all your shielding connectivity to the bridge ground with an Ohmmeter. You should have flawless connectivity from every cavity to the bridge ground or it was a waste of time.


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Posted: Sun Nov 29, 2009 3:32 pm
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Well, I'm only going by the listing for the Standard Strat on Sweetwater.com, where they claim the pup cavities are shielded. I can only go by a number of reccomendations for Sweetwater that claim they are fairly knowledgable, still I suppose it's likley they could be mistaken, I don't really know. I've never had my pickguard off my Strat yet, so I can't tell if they are right or not. All I know is the pup cavities in my jazz looked like they might have been painted with shielding paint, but it was really hard to tell, and I wasn't about to remove the pups just to look.
BTW, there was no foil of any kind on my Jazz's PG.

Update : I had started another thread earlier, which I forgot about, asking this same thing about the newest MIM Strats and shielding in the Stratocaster section of the forum, and I got an answer from forum member Martian, who, in my understanding, has a rep here for being quite knowledgable, and he replied that MIM Strats were indeed shielded, with paint in the body cavities and foil on the PG. So, that's at least two supposedly reliable sources that say they are shielded. And again I can't see them shielding the Mexican instruments and not the MIA's.


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Posted: Wed Dec 02, 2009 12:20 pm
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I had the same problem with my Road Worn Jazz Bass. I took it to the local shop and they shielded the cavity. It got about 90% of the buzz out. Cheers!


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Posted: Thu Dec 03, 2009 9:28 am
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Bathead wrote:
Well, I'm only going by the listing for the Standard Strat on Sweetwater.com, where they claim the pup cavities are shielded. I can only go by a number of reccomendations for Sweetwater that claim they are fairly knowledgable, still I suppose it's likley they could be mistaken, I don't really know. I've never had my pickguard off my Strat yet, so I can't tell if they are right or not. All I know is the pup cavities in my jazz looked like they might have been painted with shielding paint, but it was really hard to tell, and I wasn't about to remove the pups just to look.
BTW, there was no foil of any kind on my Jazz's PG.

Update : I had started another thread earlier, which I forgot about, asking this same thing about the newest MIM Strats and shielding in the Stratocaster section of the forum, and I got an answer from forum member Martian, who, in my understanding, has a rep here for being quite knowledgable, and he replied that MIM Strats were indeed shielded, with paint in the body cavities and foil on the PG. So, that's at least two supposedly reliable sources that say they are shielded. And again I can't see them shielding the Mexican instruments and not the MIA's.


Well seems you are right about the standard strats. Don't know how they are shielded. Says this is a new upgrade. Would like to see one to see what they are doing to it. Copper shielding and star grounding should cost about $150 minimum in labor to install on a Strat because it takes so long. So this must be paint like the paint Ibanez has been using for years.


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