Jazz Shielding Pictorial (Big Images Warning)

[00Funk]

I installed a John East U Retro pre in this Peavey Rudy Sarzo bass.
In short, something is seeping through. Its not hum, its not his, its like, .......well I really cant explain it. I only notice it when Im playing on my Pandora head phone amp. I can tell somethings not grounded right.
I connected all my grounds to the bare aluminum wire, coming from pickup cavities. I figured it would be grounded, since its running under the copper strip tape.
The John East instructions said NOT TO use sheilding paint, but to use foil.

My question is, should I maybe try putting a ground lug, right on top of the copper tape, and running all grounds there, or tearing it all down, and foiling the whole cavity.
Any advice would be much appreciated.

 

[pdeon99]

The John East instructions said NOT TO use sheilding paint, but to use foil.
My question is, should I maybe try putting a ground lug, right on top of the copper tape, and running all grounds there, or tearing it all down, and foiling the whole cavity.

I suggest two things. First is to eliminate ground loops. To do this, separate all your signal grounds from the equipment grounds. Don't let them touch the equipment ground except at one single point, preferably the ground lug of the cable jack. In mine, I just ran wires from any grounds that went to a pickup or a pot arm, soldered them all together, and ran one signal ground wire back to the jack. You can leave the equipment grounds where they are (bridge ground, etc). Be sure to move all pot arms away from the pot shells - unfortunately it is common practice to bend them back and solder them to a grounded shell instead of running a wire, but that creates a ground loop.

Second - yes, you might have to foil the whole cavity and the inside of the cover. A good clue for radiated noise pickup is that it changes as you point your guitar around like an antenna. I also shielded my vintage pickups, and it was worth it because now it is dead frickin' silent whereas it used to be the noisiest guitar I had heard.

 

[00Funk]

I suggest two things. First is to eliminate ground loops. To do this, separate all your signal grounds from the equipment grounds. Don't let them touch the equipment ground except at one single point, preferably the ground lug of the cable jack. In mine, I just ran wires from any grounds that went to a pickup or a pot arm, soldered them all together, and ran one signal ground wire back to the jack. You can leave the equipment grounds where they are (bridge ground, etc). Be sure to move all pot arms away from the pot shells - unfortunately it is common practice to bend them back and solder them to a grounded shell instead of running a wire, but that creates a ground loop.

Second - yes, you might have to foil the whole cavity and the inside of the cover. A good clue for radiated noise pickup is that it changes as you point your guitar around like an antenna. I also shielded my vintage pickups, and it was worth it because now it is dead frickin' silent whereas it used to be the noisiest guitar I had heard.

Thats EXACTLY what it sounds like. A ground loop.
Could you please be specific, in telling me what consist, of equipment grounds ? Is it just the bridge and pickup cavity grounds ?

I dont have much experience at this. The 2 Audere preamps I installed work perfectly. This one has a few bugs though

What are all the signal grounds ? Is it the pickup ground, input jack, and pots ?

 

[pdeon99]

Thats EXACTLY what it sounds like. A ground loop.
Could you please be specific, in telling me what consist, of equipment grounds ? Is it just the bridge and pickup cavity grounds ?

What are all the signal grounds ? Is it the pickup ground, input jack, and pots ?

Yep, you got it. One very important note is that the battery ground wire goes to the ring terminal of the cable jack - leave that part alone. This is so that it gets connected to signal ground (ie, is"on") only when your cable is plugged in.

So now, for the signal grounds, all you need to do is identify all the wires on the various pots, pickups, switches, jack, and the pre-amps that are connected directly to ground in some fashion - including bent-back pot arms soldered to shells. From each of these you are going to remove the old wire from its grounding point and bring them all together, like you did in the picture with the twist cap, but I recommend soldering. (If you have bent-back tabs, you'll need to free them up and attach a wire that you can run to join the others.) That should be it. Good luck.

 

[bgavin]

If one was going to be anal about star grounding, shouldn't the leads from each pot go to the lug, and not the shield side of the jack?

Sid, that is a great drawing. Very clear and concise.

 

[00Funk]

See the bare clear sheath, aluminum wire, on each pickup ? I have that tied in with the pickup cavity ground.
Im going to try seperating those first, and see what happens. My first thought is, thats where the ground loop is

 

[pdeon99]

See the bare clear sheath, aluminum wire, on each pickup ?

I suspect the bare wire is an equipment ground (shielding on the pups, perhaps, or grounding for metal pup covers perhaps - I can't see what's on the other side). If so, that is not likely the cause of a ground loop.

 

[00Funk]

I B confused

I should have never tried tackling this.
It sounds fine through a regular amp and cab. I dont hear the ground loop. Only when Im using headphones, and the Pandora do I hear the ground loop.

Im going to try.........taking the equipment grounds..........

I dont know what Im going to try, Im too confused.

I read what you said over and over, but I cant understand, how you seperate the grounds, when they all end up at the same place anyway.

Maybe if you just switch them around, that will fix it.

I had a ground loop in my effects chain Sunday, and I tore everything down, and reconnected it a little differntly, and the ground loop was gone.

Only logical thing to do now, is sink another 200 bucks to a professioal, who can figure it out corectly. Im just guessing, if I mess with it.

Anyone know a good tech in Dallas ?
Thanks pdeon99 for your help, Im just not grasping what your saying

 

[pdeon99]

Yeah I know it is confusing. Wish I could do a better job of explaining it.

It's strange that you hear it only through the Pandora/headphones setup. I use the same rig for practice. Try using your headphones on the amp output, just to make sure that the difference is not simply the ability to hear it. Then try switching cables. Even very low resistances will have an effect - notably the contact between the cable and the jack.

Don't eliminate the possibility that you need to shield your control cavity on all sides. If that copper strip is the only shielding, then that's not really shielding.

Good luck!

I'll take one more shot at an explanation:
Think of it this way - there are some metal parts that the music signal should not ever travel through - the bridge and strings and shielding. Then there's the low side of the music signal path. Typically you will find a pickup grounded at one place, and the preamp grounded somewhere else - but electrical noise current is flowing through ground circuit too, and some of that also flows through signal path because it is connected at 2 points (= noise). But if the signal grounds were connected to the equipment ground at only one place, then there is no way that any noise current can flow through the signal path. So that's all we're doing - simply gathering together all the signal grounds and letting them touch the main (equipment) ground only at one point.

 

[00Funk]

Thanks again for your patience and explanation. I have everything connected at one point. The Bare aluminum pickup cavity ground. See it in the pic ? Its the one going under the peice of copper strip tape. The reason why you see 2 wire nuts, is because i was just extending the bridge ground, because it was too short.

Well on second look at the pic, I think I put the pickup ground with that to.
That might be the problem. I need to put both pickup grounds under that top wire nut. The top wire nut, is my main lug. Its going under the coper tape, so that , should ground everything.

Im pretty sure, that is epoxy sheilding paint in that controle cavity.

Im going to try moving that bottom pickup ground to the top wire nut, and see if that fixes it.

John East did say, dont use sheilding paint. Maybe He knows something I bet he does

 

[00Funk]

OK I know exactly what the problem is now. I took the cover off, and all grounds are going to one point. It just looked different in the pic.
The preamp has no ground except the pots. THATS WHY it has to be foil and not paint.
Im going to tear it all down, Pay a professional to copper sheild the cavity. Then I'll put it back together myself. This time with an actual ground lug, and I will solder all joints, instead of wire nuts.

 

[Jherrera]

First off I searched all over this board and read everything to do with shielding but I still have some questions, (this is more than likely things that have been addressed as common knowledge and since I am totally new to this I just didn't get it.)

I'm playing a MIM Jazz bass.

1st I should cover the insides of the control cavity and pickup cavities with copper tape or shielding paint. correct?

The tape should overlap the edge a bit? correct?

I should use a screw and attach that black wire that is misteriously attached to my controls to that screw. correct?

My pickups each have two wires, if used in conjunction with an Audere Preamp should they just go into the four ports there or should I only attach the hots and take the commons to the ground lug screw thing?

I should run conductive wiring from the control cavity to both pick up cavities? correct?

Since its a MIM and has that routing on the surface of the bass should I use copper foil on that to connect both the neck pickup cavity and the control cavity?

Do i need to ever remove the bridge of my bass and do anything there?

Is there a better photo-step by step guide that utilizes an MIM bass?

Should I put copper foil on the underside of my pickgaurd?

Thanks guys, I really need people to simpifly this stuff for me.

-Julian
Edit/Delete Message

 

[pdeon99]

(1) 1st I should cover the insides of the control cavity and pickup cavities with copper tape or shielding paint. correct?

(2) The tape should overlap the edge a bit? correct?

(3) I should use a screw and attach that black wire that is misteriously attached to my controls to that screw. correct?

(4) My pickups each have two wires, if used in conjunction with an Audere Preamp should they just go into the four ports there or should I only attach the hots and take the commons to the ground lug screw thing?

(5) I should run conductive wiring from the control cavity to both pick up cavities? correct?

(6) Since its a MIM and has that routing on the surface of the bass should I use copper foil on that to connect both the neck pickup cavity and the control cavity?

(7) Do i need to ever remove the bridge of my bass and do anything there?

(8) Is there a better photo-step by step guide that utilizes an MIM bass?

(9) Should I put copper foil on the underside of my pickgaurd?

Let me take a crack at answering. I numbered your questions above for convenience.

(1) Yes. You can find detailed instructions on guitarnuts.com NOTE: You will not need to shield the pickup cavities if your pickups themsleves are shielded, or if they are "noiseless" by design.

(2) If you mean "up over the edge onto the top of the guitar", then yes, this is in order to bond the cavity lining to the foil on the back of the pickguard when installed.

(3) Probably. The screw just secures the wire to the foil for a good mechanical bond. Solder the wire to a ring terminal first, or use a washer under the screw head. However, the wire probably is there just to bond the controls to the cavity shielding. If you wrap the cavity foil up over the edge and put foil on the back of the pickguard, that wire will be redundant and not needed.

(4) By all means use your preamp mfr's instructions. If your preamp has hot and cold (+/-, or white/black, or whatever) inputs for each coil, I would think you should not be grounding the low side unless they tell you to.

(5) The added wire to the control cavities is only to ground the copper shielding if you wrap your pickups. Not all pickups need that extra shielding - it just happened that mine were vintage pickups that did need the shielding.

(6) You could do that, or you could replace the wire with twisted pair shielded wire, where the wire shield replaces the foil lining you would otherwise have added. Might be easier.

(7) There should already be a simple grounding wire coming from under your bridge. (You can check for continuity to your strings with an ohm meter.) If it's not there, you should add it.

(8) Not that I have seen, but that's not saying one doesn't exist.

(9) Yes. (See (2).

 

[Jherrera]

Thank you thank you thank you thank you

 

[Vic]

Let me take a crack at answering. I numbered your questions above for convenience....

Well done!

+1

 

[pdeon99]

Glad you're finding this helpful, Jherrera. Please check my previous post again - because I just now refined my answers to #1 and #3 above.
Good luck!

 

[Jherrera]

anyone done shielding with an Audere? do the commons go to the ground lug or to the predesignated spots on the preamp's board?

 

[Audere]

Pickups commons go to the connector (JZx) or green/white wire (3Bx).

The shields go to the grey/white wire.

(1) ... NOTE: You will not need to shield the pickup cavities if your pickups themsleves are shielded, or if they are "noiseless" by design.

Most noiseless pickups are humbuckers. With all humbuckers is as the frequency rises the 2 coils look less identical to each other from the perspective of an external noise source so the cancellation of noise decreases as the frequency increases.

I have scanned many humbucking pickups and the cancellation at 1 KHz runs from 6 dB to 40 dB. Lots of pickups have come in below 20 dB.

So you might want to shield the pickup cavities.

 

[00Funk]

Pickups commons go to the connector (JZx) or green/white wire (3Bx).

The shields go to the grey/white wire.



Most noiseless pickups are humbuckers. With all humbuckers is as the frequency rises the 2 coils look less identical to each other from the perspective of an external noise source so the cancellation of noise decreases as the frequency increases.

I have scanned many humbucking pickups and the cancellation at 1 KHz runs from 6 dB to 40 dB. Lots of pickups have come in below 20 dB.

So you might want to shield the pickup cavities.

Can I please trade in my U Retro for a free Audere pre ?
My other 2 Audere basses, are completely silent. I guess they dont require the extreme grounding as the U Retro.
I'll probly attempt, to sheild this myself.
How do you get the copper foil to stick to the cavity ? Spray glue or something ?
Can anyone provide a UTube link or something, of a teaching video, on installing copper sheilding ?

 

[luknfur]

...With all humbuckers is as the frequency rises the 2 coils look less identical to each other from the perspective of an external noise source so the cancellation of noise decreases as the frequency increases.
...

BOOyaw

Always a plus to run across a technical tidbit that helps to explain a reality experienced.