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Jazz Shielding Pictorial (Big Images Warning)
- Thread starter Lyle Caldwell
- Start date
Sorry Vic, I strongly disagree. The whole point of removing a ground loop is to prevent the signal ground from running through the equipment ground. If you put the pup grounds on the cavity ground lug, then you must bring ALL of the signal grounds there to achieve star grounding, including wires from those pot legs that used to soldered to the shell. Joining all the signal ground wires together (as in the drawing)is star grounding, without connecting them to the equipment ground.
This works, and the drawing is reasonably accurate. (By the way, the red X's in the drawing mean to cut or remove those connections.)
Not sure I understand what you're trying to say here, as there's no way to prevent it simply because instrument cables short the two together whether you like it or not.
Yeah, I understand the drawing.
You're missing something. I qualified my response due to the fact that the drawing shows a jazz plate, which effectively defeats a true star ground whether you want it to or not. I also said if you have a pickguard then the story is different.
If you REALLY want to isolate the shield can from the signal return then you have to do more work... you have to either use an insulating jack (with a metal plate, like on a J) or cut any shield foil around the jack to open the circuit there (with a pickguard). You didn't mention any of this, so I have to assume there's a short circuit there (which is typical).
I also strongly maintain, and challenge you to contest with data, that, if you have .0x ohms of DC resistance, you "effectively" don't have a ground loop. Period. Because for any significant voltage potential to develop over such a small resistance, the overall circuit voltage would have to be massive... enough to injure someone.
In fact, I think this is dealt with earlier in the thread as well... the whole ground loop thing is so incredibly insignificant, I seriously doubt it'd ever be audible.
You know what a ground loop is, right? It's where you have more than one "reference" and they're electrically DIFFERENT from each other, which means a potential (voltage) can be measured from one to the other. If you don't believe me, look it up. If you've got all reference points in the circuit a fraction of an ohm away from each other, at best (or worst as it were), it's just not going to be an issue. Period. White elephant, red herring, waste of time frettin' over, take yer pick.
Allright guys, my buzzing has been fixed, either pickup is almost noisless when soloed, and completly silent when equal volume, using the Fender diagram I posted with one adition,
I soldered a wire from bridge pickup cavity to the bridge volume pot, thaks for all the help.
I soldered a wire from bridge pickup cavity to the bridge volume pot, thaks for all the help.
Great! Thanks for the update, and enjoy!Allright guys, my buzzing has been fixed, either pickup is almost noisless when soloed, and completly silent when equal volume, using the Fender diagram I posted with one adition,
I soldered a wire from bridge pickup cavity to the bridge volume pot, thaks for all the help.
I'm with Vic on this one. It technically IS a ground loop, but it's so miniscule that it doesn't matter one bit. Most star grounds forget that the metal control plate/foil on the guard effectively create ground loops of their own. No biggie!
Guys, guys, guys. If you have any signal running through the control plate/foil, then you have not successfully star grounded. That's why you need to bust out those bent back pot arms. Just try it - it's not a lot of work. Less work than reading these emails I bet.
Ok, here's the short version then.Guys, guys, guys. If you have any signal running through the control plate/foil, then you have not successfully star grounded. That's why you need to bust out those bent back pot arms. Just try it - it's not a lot of work. Less work than reading these emails I bet.
1.) Unless you insulate the jack from the plate, you can't do a true star ground anyway, so desoldering and bending those legs back is a waste of time. Even then, it's shorted by the cord anyway, so no matter what you do, you're still defeated on the whole return isolated from shield thing.
2.) That said, again, I strongly maintain the whole ground loop thing is just simply not a significant concern anyway, so the importance of a true star ground is also not significant in these applications.
3.) The primary concerns are simply these; A contiguous shield can around everything, and making sure all grounds and returns are commonly connected, and connected to the can.
It doesn't need to get any more complicated than that.
Oh, also, to be fair, I have tried it in the past and not had any noticeable results, so I'm not just being contrary.
w00t! Fixed my neck pickup hum issue - guess who forgot to connect the back of the pickguard to the rest of the shielding? I put an inch long strip of copper tape under the pickguard & control plate where they adjoin, there's practically no hum at all now.
First off I just want to say a great big thank you to everyone who has contributed to this thread. My understanding of shielding has been increased dramatically and the instructions have helped me shield both my main basses within an inch of their lives.
However...there's one thing I can't seem to get rid of and that's a persistent buzz in my Warwick Streamer LX5. I replaced the stock electronics with Bartolini humbuckers and an Aguilar OBP-3. I've also shielded the control cavity but haven't yet gotten to the pickup routs or the wiring routs between pickup and control cavities.
The buzz is associated directly with how high I'm running the treble on the OBP-3. Anything above the center detent and I get noise regardless of the pickup blend. I'm not sure if it's a ground issue, an interference issue (from flourescent lights, perhaps?) or an issue with the treble boost on the preamp just being hissy.
Here's how I currently have it wired / shielded:
1. grounds from both pickups run to a lug screwed into the wall of the control cavity.
2. ground from OPB-3 run to the same lug.
3. output jack is isolated from the shielding tape
4. left the ground from the bridge taped to the cavity wall with shielding.
5. removed ground wires connecting volume and blend pots (I think it was those two, I'm doing this from memory) but I think I left the ground from the volume and tacked that to the lug as well.
You can tell from that last step that this is where my knowledge gets kind of fuzzy. My question is, if I'm running the grounds from the pickups and pre to the lug, and the cavity is shielded, do I need any ground wires at all from the individual pots, since they're all in contact with the shielding already?
Thanks in advance for any help you can provide.
J.
However...there's one thing I can't seem to get rid of and that's a persistent buzz in my Warwick Streamer LX5. I replaced the stock electronics with Bartolini humbuckers and an Aguilar OBP-3. I've also shielded the control cavity but haven't yet gotten to the pickup routs or the wiring routs between pickup and control cavities.
The buzz is associated directly with how high I'm running the treble on the OBP-3. Anything above the center detent and I get noise regardless of the pickup blend. I'm not sure if it's a ground issue, an interference issue (from flourescent lights, perhaps?) or an issue with the treble boost on the preamp just being hissy.
Here's how I currently have it wired / shielded:
1. grounds from both pickups run to a lug screwed into the wall of the control cavity.
2. ground from OPB-3 run to the same lug.
3. output jack is isolated from the shielding tape
4. left the ground from the bridge taped to the cavity wall with shielding.
5. removed ground wires connecting volume and blend pots (I think it was those two, I'm doing this from memory) but I think I left the ground from the volume and tacked that to the lug as well.
You can tell from that last step that this is where my knowledge gets kind of fuzzy. My question is, if I'm running the grounds from the pickups and pre to the lug, and the cavity is shielded, do I need any ground wires at all from the individual pots, since they're all in contact with the shielding already?
Thanks in advance for any help you can provide.
J.
As it turns out, it does seem to be a shield problem, as the buss comes and goes as I turn the bass in different directions.
I also notice that if I tap on the neck pickup I don't hear anything, but if I tap on the bridge pickup I hear that little microphonic 'pok!' sound.
What should my next step be as far as tracing the shielding problem? Is there a usual suspect when it comes to such things?
Thanks.
J.
I think you said you tried to isolate the shield can from the signal ground. I suggest you tie them together at a common point. Yeah, I know I said the star ground doesn't make a big diff, but if you're gonna' do it, you might as well do it technically correctly.
When you have a shielding problem it's one of two things. Either the shield is not contiguous, or the shield is not tied to ground.
The way a shield can works is, it takes radiated energy (i.e. RF interference) and as that energy passes across that conductive layer, it's "shorted to ground", which is what kills it before it messes with your signal.
And, Justyn, if you don't have ALL of your signal grounds touching that ground plate/shield/can at ONLY ONE point, then some of that shorted-to-ground RF interference will get into your signal path. That's why it matters to lift those pot lugs away from the shell, join all your signal ground wires together, and connect them to ground only at one place - preferrably at the output jack - that way you don't need to isolate the body of your output jack from the shield. I can't tell from your description if you have done that yet.
Thanks gents. I'll do an exhaustive inspection of my current shielding and report back soon.
But first, I grout! Gotta finish the tile floor in the new sunroom!
Strappin' on my kneepads,
J.
But first, I grout! Gotta finish the tile floor in the new sunroom!
Strappin' on my kneepads,
J.
I tried a little test tonight. I stripped a piece of copper wire and wrapped it around the threaded portion of the jack that protrudes into the body cavity. Then I pushed both ends under the jack where tension would keep them resting against the shielding. The idea was to see if tying the shielding to the jack would help without going in, unscrewing the jack, applying more shielding, and then tightening the nut on the jack again which is a bit of a cumbersome process.
No change. I still get directional hum which becomes noticeable when I turn up the treble control on my OBP-3. It's possible my little experiment just used flawed logic, so correct me if I was in error there.
Other information which may prove helpful:
1. When I bypass the preamp and run the bass passive I get no noise.
2. The pickup cavities have not been shielded yet.
Question: If I've got a pot touching the shielding tape, and there's also a wire from the pot running to the common grounding lug, could that cause noise? I *think* I've gotten rid of any spots where I had a pot both shielded and wired, but I need to go back and make sure. Maybe tomorrow I'll take pictures.
Thanks again for all the help,
J.
No change. I still get directional hum which becomes noticeable when I turn up the treble control on my OBP-3. It's possible my little experiment just used flawed logic, so correct me if I was in error there.
Other information which may prove helpful:
1. When I bypass the preamp and run the bass passive I get no noise.
2. The pickup cavities have not been shielded yet.
Question: If I've got a pot touching the shielding tape, and there's also a wire from the pot running to the common grounding lug, could that cause noise? I *think* I've gotten rid of any spots where I had a pot both shielded and wired, but I need to go back and make sure. Maybe tomorrow I'll take pictures.
Thanks again for all the help,
J.
