I had a black trim bass that had so much paint (or whatever it was) on the tailpiece that the allen screws from the bridge weren't making contact with the tailpiece itself which is the way it grounds.
We've also seen some dissimilar metal problems (in high humidity) where the plain steel height screw contacts the tailpiece. For this reason, we recently changed the screw to stainless steel with a cone point which will continue to make better contact over time.
In testing, we've not had good results with aluminum tape used like this, as compared to copper, which also has the benefit of being able to be soldered.
The main area that is problematic as far as ground loops (73's Bob, WD6GDL here . . . ) is the back of the pickguard. First, the pots already have a ground lead; if you allow them to make contact at the mounting bushings you get a loop. Second, the edges can make irregular, intermittent contact with the foil in the pocket; this can be avoided by keeping the foil slightly away from the top surface of the instrument. Finally, if any of the pots, pickup shells, or shielding from the wiring inadvertently touches the pocket foil, you have the potential(!) for problems.
Lastly- and I know you already know this, John- DC resistance is not the end-all indicator here, as you're trying to keep RFI and ESI out at much higher frequencies. Those overlapped aluminum foil edges with adhesive between them are nice little capacitors! Then there's the point that neither copper nor aluminum is going to block EMI, which is very commonly the source of noise due to amplifier power transformers. Time to break out the mu-metal!
Any experience with shielding your pickups?
Moderators: rickenbrother, ajish4
Could you not just wire in a coil that is reverse wound , with no magnets and wire that into the circuit in series ? Wouldn't that stop the 60 cycle hum ?
That is what I was refering to in my post about the "Alembic Way". They do that in their Series I and II electronics with a dummy coil between the two single coil pickups.
UPDATE:
Well, sort of. I still haven't picked up the bass yet. The luthier is working out "some minor glitches". I don't like the sound of that!
I'll pick up the bass tomorrow morning and test her out on Sunday. The bass was always quiet here at home. One of the sound guys pointed out that BOTH of the churches I play at have an airport tower located about 1/3 of a mile away. COULD that actually cause a problem so far away?
Good old Grumman!
Well, sort of. I still haven't picked up the bass yet. The luthier is working out "some minor glitches". I don't like the sound of that!
I'll pick up the bass tomorrow morning and test her out on Sunday. The bass was always quiet here at home. One of the sound guys pointed out that BOTH of the churches I play at have an airport tower located about 1/3 of a mile away. COULD that actually cause a problem so far away?
Good old Grumman!
"Freedom of expression is important, but I have learned that people want to know how much you care before they care how much you know."
The only time a bass player gets noticed is when he stops playing.
The only time a bass player gets noticed is when he stops playing.
-
lyle_from_minneapolis
- Advanced Member
- Posts: 2530
- Joined: Sun Nov 19, 2006 7:13 pm
I once received this advice about finding and using copper tape for shielding from a friendly member of the RIC forum:
"Stewart-MacDonald Guitar Shop Supply, part #0028, 2" wide by 180" long. Only $8.79 a roll; call 1-800-848-2273, they'll send you a catalog. Or,you can check out stewmac.com, their web site is excellent. And I overlap the tape by 1/8"; the adhesive is conductive, as well. BUT...be careful; this stuff is as sharp as a razor blade!"
"Stewart-MacDonald Guitar Shop Supply, part #0028, 2" wide by 180" long. Only $8.79 a roll; call 1-800-848-2273, they'll send you a catalog. Or,you can check out stewmac.com, their web site is excellent. And I overlap the tape by 1/8"; the adhesive is conductive, as well. BUT...be careful; this stuff is as sharp as a razor blade!"
Here is where I hide my music:
http://www.soundclick.com/MarkKaufman
http://www.soundclick.com/MarkKaufman
Could you not just wire in a coil that is reverse wound , with no magnets and wire that into the circuit in series ? Wouldn't that stop the 60 cycle hum ?
It helps a little if it's placed close enough to the active pickup. But which pickup do you place it near?
Then there's the problem of an extra winding- a non-productive one at that- changing the sound. John Suhr offers the "Backplate Silent Single Coil (BPSSC) System" for Fenderesque guitars but that works because of the close proximity of all the pickups to the back of the guitar.
Airport tower transmissions usually aren't much of an issue as they don't use a bunch of power; they use VHF AM which is more or less line of sight since airplanes are either in the air or nearby the tower.
Radar is a 'nother issue altogether.
Awhile ago we were bothered in the studio on stormy or foggy nights with a noise that swept by every six seconds. I finally figured out it was ship's radar as our location on a hill overlooking the Pacific shipping lanes was directly line-of-sight. The solution was an extra cord stuffed into the underwear band making skin contact and plugged into a spare jack for the sleeve ground connection. Neither the foot nor the hand worked near as well as the waist, and it was a subject of great mirth as well when we handed someone a cord and told them where to stick it!
It helps a little if it's placed close enough to the active pickup. But which pickup do you place it near?
Then there's the problem of an extra winding- a non-productive one at that- changing the sound. John Suhr offers the "Backplate Silent Single Coil (BPSSC) System" for Fenderesque guitars but that works because of the close proximity of all the pickups to the back of the guitar.
Airport tower transmissions usually aren't much of an issue as they don't use a bunch of power; they use VHF AM which is more or less line of sight since airplanes are either in the air or nearby the tower.
Radar is a 'nother issue altogether.
Awhile ago we were bothered in the studio on stormy or foggy nights with a noise that swept by every six seconds. I finally figured out it was ship's radar as our location on a hill overlooking the Pacific shipping lanes was directly line-of-sight. The solution was an extra cord stuffed into the underwear band making skin contact and plugged into a spare jack for the sleeve ground connection. Neither the foot nor the hand worked near as well as the waist, and it was a subject of great mirth as well when we handed someone a cord and told them where to stick it!
Great story, John. Simple solution too!
Yes, I am aware DC resistance is not the only criteria for this problem (your stated RFI, and to a lesser extent ESI) but a basic requirement, and that aluminum is not (by far) the best because it won't take solder, but Kalamazoo is not a big metropolitan area so RFI is not a concern around here. My main problems were neon and florescent lighting, dimmers, ANY computerized device, and monitor/tv displays. In my practice room, the TV on the other side of the wall 8 feet away caused loud interference! My efforts solved those problems, but I highly recommend getting the copper tape from Stew-Mac and soldering as Bob did.
Mu-metal! Finding and affording it is the challenge there! And other than NYC or LA, etc., probably overkill.
Yes, I am aware DC resistance is not the only criteria for this problem (your stated RFI, and to a lesser extent ESI) but a basic requirement, and that aluminum is not (by far) the best because it won't take solder, but Kalamazoo is not a big metropolitan area so RFI is not a concern around here. My main problems were neon and florescent lighting, dimmers, ANY computerized device, and monitor/tv displays. In my practice room, the TV on the other side of the wall 8 feet away caused loud interference! My efforts solved those problems, but I highly recommend getting the copper tape from Stew-Mac and soldering as Bob did.
Mu-metal! Finding and affording it is the challenge there! And other than NYC or LA, etc., probably overkill.
We could get into the FCCs huge fiasco putting DTV allocations on the VHF-Lo band (ch. 2-6) with their susceptibility to noise! Remember AM radio on a day a thunderstorm moved through? That noise has significant energy in the VHF-Lo band and to a digital tv receiver, the impulse noises (lightning, bad AC pole insulators, noisy neon lights, any bad AC connection, dimmers, florescent lights, arc welders in the neighborhood, and on and on....) look like digital data and totally screw up the decoding of the broadcast signal. So when a bad storm is moving through and you need to get pertinent weather info to your audience, your digital signal is wiped out by the storm you need to warn them about!!! Of course, it has been decades since the FCC was run by engineers instead of appointed polititians....
Solution? After analog dies, spend more millions buying a new digital transmitter and antenna to move to a VHF-Hi allocation where the energy from those sources is not significant enough to interfere. Conversion costs x 2!!!
Solution? After analog dies, spend more millions buying a new digital transmitter and antenna to move to a VHF-Hi allocation where the energy from those sources is not significant enough to interfere. Conversion costs x 2!!!