Quieting the Jazz Bass with metal cover/guard

[sthayashi]

I've read the original Guitar nuts site many years ago, and I revisited it recently and thought: Man, I should do something to make my bass guitar quieter. Some notes if you're not familiar with the Jazz bass, they look like any of the two pickup basses here. Note the metal plate that the controls are on.

So this past weekend, I took apart the control panel and did some experimenting. First, I put some aluminum foil in the cavity. I didn't glue it down since I didn't want to fully commit to the shielding, but it did wrap all the way around the cavity and came up over the top where I screwed the cover down. I figured that it should do the job (maybe?) in a controlled setup, i.e. my living room, and if it worked, I could cement it down easily. Sadly, no such luck. It did nothing to the buzz.

Next, I looked carefully at the wiring, and I'm not sure that there are any ground loops I can remove. The metal plate acts like a ground plane for the pots. Each pickup ground is connected to the shell of the volume pots, and the bridge ground is connected to the tone pot shell.

The Output jack's ground line isn't even wired up! It uses the metal plate to connect to the ground.

My questions on it are as follows:

Would it still be a good idea for me to consolidate the pickup and bridge wires? Or is it sufficiently "star" grounded?

Should I reexamine shielding again and try and do a proper job?

Or should I wait until I can afford newer/nicer pickups that are less prone to buzzing?

FWIW, I'm not doing the blocking cap protection. It doesn't really seem worth it until I at least get an isolated output jack.

[ashcatlt]

Well, some of those two pickup basses on that page are Jazz/Precision hybrids. Is yours a more standard Jazz with the two SC pickups?

Anyway, most of the noise comes from the big long antenna that's coiled around each of the pickups. It's a good idea to shield the control cavity, but I wouldn't expect it to do much unless you're also shielding the pickup cavities as well. Should be easy to get some foil in behind the neckmost pickup under the pickguard. I don't know what's under that bridge pickup or what it would take to shield that area.

We usually don't worry about ground loops around here. Your system (as described) should be fine, though ChrisK used to warn against using a shield (the metal control plate) as a signal conductor, mostly for "best practices" reasons.

[newey]

Ash is right, job #1 is to shield the pickup cavities, insofar as you can on a JB.

The use of the Control Plate as a ground was the standard Fender wiring back in the day- and may still be, for all I know.

support.fender.com/diagrams/basses/0131800A/SD0131800APg2.pdf

Notice that there's no negative jack wire . . .

I've never noticed JBs to be particularly noisy, so yours sounds out of spec, noise-wise. If it's noticeable enough to bug you, it's a problem.

While, electrically speaking, it may just be a matter of "best practices" to not use the plate as a signal carrier, this assumes one is getting a good signal ground through the plate. If not, that could explain added noise.

Over time, things corrode, get finger oils on them- and the pot shafts may have been only marginally connected to the plate to start with.

It's easy enough to run a separate ground wire from the outjack neg. to any of your pot shells (or to a star grounding point if that's what you're doing.). Probably worth a try.

And, as Ash noted, don't worry that this creates a ground loop- if a questionable ground is the problem, this ought to solve it.

EDIT: And I almost forgot . . .

sthayashi-

Hello and Welcome to G-Nutz2!

[sthayashi]

Ash,

The bass guitar is a standard Jazz bass (it actually IS a Fender Jazz bass).

Newey, that diagram is exactly how my setup looks. I took it apart to look at it and work out how to best shield it and remove any ground loops and as you can see, there are none.

I think Ash is right about the antenna part though. The buzz is dependent on where I'm standing and where I'm facing. The turning down the tone reduces the buzzing (or at least the HF parts), but moving around does a better job. Of course, I'd rather fix the problem rather than just work around it.

Shielding the pickup cavities sounds like it's the best thing to do. Of course it's a little more involved than removing the controls since I'll have to remove the strings as well. I'll probably also buy some copper tape to make life easier since I'm not a fan of cement or spray glue.

I'm also kicking around the idea of switching my pickups to the Alumitones. Is this a good idea/bad idea from a buzz killing perspective?

Thank you for the helpful advice and the warm welcome.

[ashcatlt]

I'd probably take the jack sleeve to the "grounded" lug of the V pot, but I'd like to make sure the strings/bridge conducted to that point as well.

Do you have a meter? It's worth at least checking the resistance between the strings/bridge and the output jack. You are the closest EMI/RFI noise source and the "string ground" helps to take you out of the picture.

I've never taken a Jazz bass apart, but it seems like those must be plastic covers over the actual pickup coil, no? If nothing else, you could jam some foil up in there and make sure it gets grounded (connected to jack sleeve) someway.

And then you reminded me that I was going to ask if anybody had any experience with the Alumitones. I haven't heard anything around here, and haven't looked far enough into it. How do they work?

[gumbo]

...both my JB-s hum a little...never enough to be a problem on stage, and since the main guy who complains about it at rehearsals actually plays a banjo, I ignore it.... ;D

...thought about changing pickups, but never got around to putting it on the (vast) schedule of things to do..

[newey]

And then you reminded me that I was going to ask if anybody had any experience with the Alumitones. I haven't heard anything around here, and haven't looked far enough into it. How do they work?

Lace is (I suspect purposefully) vague about how they actually work. They claim that it is a "current driven" technology rather than the voltage-driven standard pickup.

All I could gather is that the aluminum "face" of the thing functions like a single winding with really big wire. It produces a low-impedance (yet passive) signal which is then inductively coupled to a high impedance coil underneath the face, which is still much smaller than the windings on a regular coil. This is said to produce a "Lo-Hi" impedance pickup.

They claim broader frequency response, 95% less copper wire ("green"), half the weight, and general all-around goodness . . .

If you search back far enough, we have had some discussion of these. ChrisK said he put a set in a Strat, and they lasted only about half an hour before he took them back out and stored them in a box. He didn't like the tone as compared to noiseless SCs. Others have lamented the tone as well.

What I drew from this was they're a "love 'em or hate 'em" proposition tone-wise. They should be virtually noiseless, however.

All of the discussion, as I recall, related to the Strat version, and compared them to Strat SCs. And for Strats, it's all about that SC "sparkle". The bass versions might be a different story altogether, since Lace claims an improved low-end response, and the high-end tone Strat players seek isn't so much of an issue.

[Yew]

If you want to stop the hum on a Single coil, couldnt you use a dummy coil?

[sthayashi]

From various youtube videos of the Lace Helix Basses, I think I'll be happy with the alumitone's tone. So no worries there, I just need to find room in the budget for them after Christmas presents have been paid for.

Ash, I do have a meter and I'll measure the resistance of of the strings to the output jack. I expect it should be as close to 0 as my meter gets.

Yew, can you elaborate on the dummy coil?

[newey]

Here's a link to Gunther's dummy coil experiments of several years ago:

guitarnuts2.proboards.com/index.cgi?board=wiring&action=display&thread=1693

If you are set on a pickup swap to noiseless pickups, there's no point to pursuing the dummy coil idea.

Basically, it works just like those "stacked" HBs, where only 1 coil senses the string movement, the other coil is only there to buck the hum. By removing the magnet from a coil, it no longer will have a signal induced in it from the string motion, but the coil will still help cancel hum when the dummy is RW with the original.

The real issue is whether the added dummy coil sucks tone from the string-sensing coil. Gunther did this to a Jazz bass (coincidentally . . .) and reported no change in tone, but with a SC Strat pickup, he reports an undesirable difference. YMMV, of course . . .

[sumgai]

yew,

Not to mention, that even if the dummy coil were a viable idea from the standpoint of hum reduction, there's the little issue of inserting it into the guitar's body. In a Strat, there's room galore, in the pickup cavity or the springs cavity. In a bass, there's no prexisting cavity, so one would have to drag out the router, set up a jig, don his safety googles, etc. etc. yadda yadda.... A true Nut would do this in a heartbeat, but some folks do have a penchant for considering the 'return on investment'.


But that brings up another point....

st, does your bass hum when both pups are turned up to max volume? I also have a JB (but fretless), and it's quiet as a mouse when both pups are on. When I go out to play, I've found only one venue where it does hum, and I've isolated that to the cord/amp supplied by the host band at a local jam session (where I can't bring in my own amp and stuff).

Have you tried other cords, other amps, playing in other locations, etc?


HTH



And since I've been remiss lately, I'll say only this:

Hi, and to the NutzHouse!




sumgai

[cynical1]

To expand on SG's thought, years ago I had a Fender Jazz, and I distinctly recall that if I turned the volume completely off for either the neck or bridge pickup, essentially selecting only one pickup, I had noise. If I brought up the aforementioned de-selected pickup volume up to around 3 the noise dissipated.

I had a noise issue similar on my Peavey bass, and this cured the noise problem as well.

Sound familiar to anybody else?

HTC1

[4real]

Dec 8, 2010 15:58:08 GMT -5 cynical1 said:

To expand on SG's thought, years ago I had a Fender Jazz, and I distinctly recall that if I turned the volume completely off for either the neck or bridge pickup, essentially selecting only one pickup, I had noise. If I brought up the aforementioned de-selected pickup volume up to around 3 the noise dissipated.

I had a noise issue similar on my Peavey bass, and this cured the noise problem as well.

Sound familiar to anybody else?

HTC1

Yes...my bass player plays a vintage Jazz and it will make noise unless both pickups are on. These Pups are giant SC picups like a strat or any other fender and sufers the same problems, possibly more so because they are so big...run two and they are generally humbucking.

A cover plate doesn't really help as a rule, hardly ever see a tele player with the ashtray on for instance and the chrome cover on a tele neck pup does nothing much either!

The "cover" though was useful for soem players who would sometimes put rubber 'erasers' under there to get a dull thuddy more upright sound or response...good for some of that "Motown sound"...but then you lose 'sustain' and a good player can mute with their fingers for a similar effect.

There are probably noiseless pickups available, likely stacked HB's like fender SCn's or something...but just new but standard SC pups to the same design are not going to do anything in that regard...it's somewhat the nature of SC pickups.

My bass is a kind of musicman type clone, very funky sound with a giant single HB format pickup and a jazz kind of wiring with dual vols for each coil for mixing the coil split..so effectively two single coils...and same thing, got to have a bit of a mix of both coils to be quiet...or stay well away from TV's monitors, fluro bulbs and transformers (possibly in your amp) and anything else that might set them off if you really have to use just one pup at a time.

Unfortunately in this world it can be near impossible to avoid some kind of noise...even with my HB quiet guitars...I often have my mobile phone in my pocket and I can hear it searching for reception every 15mins or so through the pups.

I know that sometimes wiring can go wrong though, so perhaps check it out...I suspect my bass player could do with a rewire and perhaps some new pots as there is a bit of crackling there. If you are after a more funky sound than on offer from the combination of pups...I wounder what some kind of phases switch might offer in a push pull pot, maybe with a cap to taste to get a brighter sound yet still being humbucking...hmmm

[sthayashi]

Wow, so many people posting suggestions. Here's the update.

Ash, I checked out the resistance of the bridge to the jack. My POS meter claims 6 Ohms, but the meter itself claims 4 Ohms for shorted leads. Time to save money for a Fluke?

SG & Cynical, no such luck with going full volume or not. The buzzing is definitely still there. And yeah, I tried other settings as well. The tone knob really seems to affect it the most.
BTW, your description of the basses you've used sound like the two pickups were acting like a sort of poor man's HB. But I presume and digress.

SG, I have not tried different cable/amp/location. I don't have a lot of amp options nor location options. I'm certain location has something to do with it. Moving around or even turning my body from one direction to another can greatly affect the noise I get.

4real, my noise source speculation is that it comes from the CFLs I have in the house. I have almost no incandescent bulbs around anywhere anymore.

[ashcatlt]

Yeah, the two pickups should be RWRP from one another, exactly like the coils in an HB.  Does your noise get louder with both volumes all the way up?  That would indicate they are not RWRP, and unless it's been "modified" somebody at Fender's QA dept screwed up. 

You were likely correct in your first post that the Tone seems to help by attenuating the more annoying high frequency harmonics in the buzz.  A bigger cap would have an even stronger reduction, but you're throwing the baby out with the bathwater.

I wouldn't think that 2Ω -or even 6 - wold be a deal breaker.  You could try clipping a wire between the bridge and the jack or cable and see if that helps.  Actually, you could just touch the metal barrel of the cable!  If this helps, you might need to make the internal bridge ground more efficient.  

Speaking of cables, have you tried more than one?  How bout the amp?  Do you have another to try?  Can you plug it in somewhere else and try it?

Yes, those CFLs could be part of your problem.  They're a lot more efficient, but the devil when it comes to audio.  High impedance and long wires just make it that much worse.  Time to switch to LEDs!

[sthayashi]

Is there a good way to verify whether a pickup is RWRP? Use a fridge magnet and see that one pickup attracts and the other repels? What about the winding?

I think the noise gets a little louder when both are at full volume. It doesn't seem to make that much of a difference. I'll try and record sound or a video of what the noise looks like and what different pot settings sound like.

The bass itself is over 16 years old and Made in Mexico at that. It's very possible that Fender QA screwed up.

I'll try different amps and cables tonight and see what I get. I'm not holding out much hope since I figure noise coming from cable or amps would not be affected by the potentiometers. I might see about how much noise an open cable makes.

CFLs are going to stay in my house. I just hope that noiseless pickups are. :-)

[cynical1]

Dec 9, 2010 15:14:37 GMT -5 sthayashi said:

Is there a good way to verify whether a pickup is RWRP?

Well, the simple test for a Strat set, as I recall, is to put them pole to pole. Of the three, the one that attracts the other two is RP. This does not verify RW, but generally the two go hand in hand.

HTC1

[newey]

Is there a good way to verify whether a pickup is RWRP? Use a fridge magnet and see that one pickup attracts and the other repels? What about the winding?

You don't need to worry about the reverse winding, since if the polarities were the same but the windings reversed, they'd be out-of -phase and you'd certainly hear that. If one is reverse wound, it will also be reverse polarity and vice versa.

With only two pickups to check, a fridge magnet will do the trick- so long as you don't flip the magnet while doing the testing. If the magnet attracts one and repels the other, the 2 are RP with respect to each other; if the magnet attract both or repels both, then they're not.

[sthayashi]

As I might have expected upon reading some of this thread's Jazz Bazz owners... My pickups do not appear to be reverse polarity. A fridge magnet appeared to attract to both of them. Given that I have not heard a reduction in hum when both are on full volume, that really is to be expected.

I don't know that there's any easy way to fix this (rewinding the pickup is NOT an option).

Oh, still haven't tried different wires or amps, but it seems obvious where the problems lie.

[4real]

Be careful with "fridge magnets"...those thing rubberized ones for instance are magnetized in alternate strips...so both polarities on both sides and will stick to anything~!

Depends on the pickups...it seems that this must be a "copy" and not an original fender...but it seems strange that any manufacturer would miss the opportunity to have them RWRP.

They wouldn't need to be rewound, just the wires switched to be "reverse wound" but to avoid being OoP you would need to reverse the magnets...this may be possible but depends very much on the way they are wound and what you are up for.

A replacement set could help...but again only with both pickups on for an HB effect...but really, sounds like you are operating in a really noisy environment there....noise could also be getting in through the wiring and cables and amp...changing the light bulbs at least in the area you play most is probably a good idea...those CFL's give me a headache anyway...LED lights perhaps or there seem to be other alternatives. Perhaps turn off all these sources of noise (lights, computers, etc) and see if that makes a difference

[sthayashi]

I just checked again with a magnet that came unglued from one of our refrigerator magnets. It attracts on one side and repelled with the other. But it was the same for both pickups.

Dunno if this is a "copy" or not, but it's damn good copy if it is. It says Fender, made in mexico, and it has a serial number. I'm not 100%, but I believe I bought this in a music store in Akron about 13-14 years ago.

I tried turning out all the lights and it still made the same amount of noise.

I'm really tempted to record a video for you all to show everyone here the type of buzzing I'm getting.

[newey]

If you've had it for 13 or 14 years, and it says "Fender" then that's probably what it is. And it's highly unlikely that it came from the factory without a RWRP pickup. If you didn't buy it new, it is of course possible that someone may have replaced one or both pickups, and perhaps didn't use a RWRP one.

If they're original, I'd suspect your test to be the problem moreso than the pickups. As Cyn mentioned, the best test is to oppose the 2 pickups themselves, assuming you're going to be dismembering it.

But more basically, if we are talking about inordinate amounts of hum in all switch positions, then there's a noise issue apart from just the question of whether the 2 pups are hum-canceling when combined.

Your environment may be unduly noisy, so trying a different environment, eliminating CFLs and other potential noise sources, different cables, etc are all good suggestions.

And a good shielding job may also help.