Shielding - How do you know it will help?

[somebrains]

I just moved a preamp from a bass with GZR PJs to one with Nordstrand Bigmans.
I need to get a roll of 3M copper tape, degreaser, or rubbing alchohol.

The same preamp had been in a bass with a pair of SD Alnicos previously.
I thought that bass had noisy pickups, the Bigmans are worse when it comes to hum.

The hotter or bigger your passive pickups get, you find more reasons to upgrade your cavity shielding.
You also think about going back to active EMGs a lot bc they really are a simple solution + they come in more flavors now. This happens when things start to go wrong, but a copper job ain't helicopter engine rebuilding.

 

[BlueTalon]

Copper Foil Tape EMI Shield Single-side Conductive Adhesive Roll 12mm*50m | eBay

 

[Killed_by_Death]

The stuff I bought was 2" wide, 180" long, for $5.

 

[1958Bassman]

The thing about shielding is that people usually do this to the instrument, but don't concern themselves with the whole signal path from the instrument to the ground stake(s). I included the (s) because the NEC (National Electrical Code requires two stakes on new work, not more than 8' apart, on an unbroken conductor form the panel to the last stake. If the grounding (the green or bare wires) and/or grounded conductors (the neutral is usually white, but it can be other colors) in the building have resistance between the outlet and the panel or the neutral buss isn't making good contact with the ground in the panel, all of the shielding in the world won't help- the instrument will be shielded WRT the pickups to the jack, but the jack and cable(s) will still prevent the shielding to be grounded as well as they need to be (called 'at the same electrical potential') and this may result in less noise, but it won't be gone. It could even be worse.

Another thing that's needed- if the pickups have individual, unshielded + and - wires, the ends that aren't enclosed in a shielded space need to be twisted- telephone wires have been twisted for decades without shielding and they reject hum & noise well- look into CMRR (Common Mode Noise Rejection) for more info. Network cabling is twisted pairs, too- most of it is unshielded.

It's a good idea to have a few tools in the rig- pliers, screwdrivers and a circuit tester like this come in handy to find out if the circuit is wired correctly or if it has lifted neutral or ground- they're available all over and the price varies, but the cheap ones work as well as the more expensive ones.

http://static.davis.com/large_images/20021_22.jpg

 

[Killed_by_Death]

Yeah, I remember the acronym for LAN wire was/is UTP - Unshielded Twisted Pairs

 

[Killed_by_Death]

I agree it works. It will do nothing for 60hz single coil hum, but if you do it right and ground everything correctly it keeps RF out.

This is exactly why I started this thread. Isn't 60 Hz hum a thing of the past that came in through the power on amps that weren't properly isolating the "ripple" from the instrument?
Isn't all the noise today electromagnetic interference & not actually caused by the 60 Hz of the power grid?

Has anyone ever effectively shielded a single coil Precision bass?

Shielding worked for the noise I was experiencing here at home, but on a humbucker-equipped bass.
I'm not sure if it would do any good for the Big Singles in my current Ibanez.

I just cranked up the gain on my amp & soloed the bridge pickup.
Touching strings or bridge did nothing to quiet the noise.

 

[Rockin John]

I don’t know, on the bass I just finished building a couple months ago, I used foil, and the only solder points I have are where I connected the ground wire. I have consistent conductivity between all discrete pieces of foil, due only to the adhesive. I must get a good brand of foil.

The reason I suggested multiple solder points was it’s been shown that foil adhesive can be of variable quality. Also, to get a good electrical joint it requires excellent adhesion between foils and this is not always possible around the contours of bass guitar cutouts. In addition, over time, the adhesives can dry out so altering the conductivity.

My solder blobs are a belt-and-braces approach to preventing a variety of conductivity issues.

Magnetic field strength varies according to an inverse square Law, but not if you’re too close to the field!

 

[Rockin John]

This is exactly why I started this thread. Isn't 60 Hz hum a thing of that past that came in through the power on amps that weren't properly isolating the "ripple" from the instrument?
Isn't all the noise today electromagnetic interference & not actually caused by the 60 Hz of the power grid?

Has anyone ever effectively shielded a single coil Precision bass?

Shielding worked for the noise I was experiencing here at home, but on a humbucker-equipped bass.
I'm not sure if it would do any good for the Big Singes in my current Ibanez.

I just cranked up the gain on my amp & soloed the bridge pickup.
Touching strings or bridge did nothing to quiet the noise.

As a sort-of side issue.....
Without sounding too obtuse, clearly the best way to reduce noise pickup is for players to keep as far away from the noise as is possible! I suppose this is not always thought of when on stage. And, whoever lays the cables for the band should be aware of the need to route the mains supply away from the musicians as possible.

 

[Rockin John]

The thing about shielding is that people usually do this to the instrument, but don't concern themselves with the whole signal path from the instrument to the ground stake(s). I included the (s) because the NEC (National Electrical Code requires two stakes on new work, not more than 8' apart, on an unbroken conductor form the panel to the last stake. If the grounding (the green or bare wires) and/or grounded conductors (the neutral is usually white, but it can be other colors) in the building have resistance between the outlet and the panel or the neutral buss isn't making good contact with the ground in the panel, all of the shielding in the world won't help- the instrument will be shielded WRT the pickups to the jack, but the jack and cable(s) will still prevent the shielding to be grounded as well as they need to be (called 'at the same electrical potential') and this may result in less noise, but it won't be gone. It could even be worse.

Another thing that's needed- if the pickups have individual, unshielded + and - wires, the ends that aren't enclosed in a shielded space need to be twisted- telephone wires have been twisted for decades without shielding and they reject hum & noise well- look into CMRR (Common Mode Noise Rejection) for more info. Network cabling is twisted pairs, too- most of it is unshielded.

It's a good idea to have a few tools in the rig- pliers, screwdrivers and a circuit tester like this come in handy to find out if the circuit is wired correctly or if it has lifted neutral or ground- they're available all over and the price varies, but the cheap ones work as well as the more expensive ones.

http://static.davis.com/large_images/20021_22.jpg

The whole subject of electromagnetic interference is extremely complicated and falls well outside of most bassists, I would think. There are, tho, I believe, lay-mens’ guides to the subject, but bass practice is probably more profitable in the long run! Ha ha.

The Common Mode Rejection Ratio is the ratio of the wanted signal through a system and the unwanted signals (the noise). As noted the CMRR can be improved by twisting signal hot and cold wires together and running them inside the instrument. However, the cable runs are so short that it hardly makes much difference whether they are twisted or not (tho it doesn’t harm to twist them!).

 

[DiabolusInMusic]

We can have both types of hum pickup - inducted hum into the windings and cables, and also from ground loops that make tuned antennas. The ground loop issue is why cavities and control plates should be grounded ONLY at a single point, and the theory behind star grounding. Our runs are so short that anything picked up from a 4" ground loop is probably inaudible, but it doesn't hurt to be careful!

I have had only good luck from using Copper foil with conductive adhesive from Stew-Mac. The first time I used it, the bass was so quiet that I thought I had shorted the output!

Don't forget to twist the wires from the pickups a few times to get a little common-mode rejection as well.

I love Stew-Mac but nobody should buy shielding supplies from there. Their tape is way too overpriced and their paint is low-quality for a premium cost. Get your tape from Ebay and use MG Chemicals Supershield.

This is exactly why I started this thread. Isn't 60 Hz hum a thing of that past that came in through the power on amps that weren't properly isolating the "ripple" from the instrument?
Isn't all the noise today electromagnetic interference & not actually caused by the 60 Hz of the power grid?

Has anyone ever effectively shielded a single coil Precision bass?

Shielding worked for the noise I was experiencing here at home, but on a humbucker-equipped bass.
I'm not sure if it would do any good for the Big Singes in my current Ibanez.

I just cranked up the gain on my amp & soloed the bridge pickup.
Touching strings or bridge did nothing to quiet the noise.

Plenty of people have done perfect shielding jobs on single coil Precision basses. If I like single coil P's, I would have done one myself. The pickup will still be susceptible to 60hz noise though. Shielding address RF interference. Humbuckers address 60hz noise. Neither one will resolve both issues so both must be used in tandem to have a fully silent bass. While both issues are the same at a theoretical level, for our application, these are two separate issues with two separate solutions.

The question of "do I need shielding?" can easily be answered by checking if you have a noise that stops when you touch metal/strings/bridge. If you do not, shielding will not address your issue.

 

[Killed_by_Death]

'
"do I need shielding?" can easily be answered by checking if you have a noise that stops when you touch metal/strings/bridge
'

I agree with this last statement, but with the caveat that the bridge has to be electrically grounded to the controls & shield side of the output jack.

I also agree that Stew-Mac is not the place to buy shielding tape, or most things actually, unless they're the sole source.

It would appear my Ibanez Premium has decent shielding (looks like thick graphite paint), but is mildly noisy if a pickup is soloed. (Nordstrand Big Singles)

This separation of 60 Hz hum from other noise is what I'm not getting. Even if It's a 60 Hz tone, unless it's coming in through the power lines, it's EMI or electrostatic noise (what you always call RF interference).
Humbuckers also address most electrostatic noise (or what you call RF interference), not exclusively what people call "60 Hz hum".

Someone explain why if touching grounded strings doesn't change the noise that shielding won't help?
I have an open mind, but I like to hear/read reason...
How is that noise different from other EMI/electrostatic noise?

60 Hz hum through the amp's power lines used to be a thing, but what people are calling 60 Hz hum now is being induced through the air, so it's EMI or electrostatic interference.
Case in point, Chicory Blue was running her bass on a battery-powered amp & still had noise, so the noise was coming in through the airwaves, i.e. EMI or electrostatic noise.

FWIW, this is a 60 Hz tone:



That is not the tone I'm hearing with my single coils.

 

[somebrains]

Big Singles amplify the issues a regular J has, along with giving you that glorious tone.
I just switched between a couple basses for perspective.
One has Bigmans set to single, the other has a J from a GZR set.
Popped both preamps to passive bc there's varying levels of hiss amplified when they're active.

Ironic but my Electric Blue is way noisier than the SVP-CL setup, so I could leave the basses alone but Nordstrand and SWR go better than Nordstrand and Ampeg with my setup.

I should go get a Furman, but to a carpenter every problem looks like a nail, I wrench on the bass to ignore complementary solutions.

 

[Killed_by_Death]

IMO, other than radio stations, the noise you usually hear is 60 cycle off the powerline.
Most amps have filtered power supplies and using an outboard filter does nothing until you get into high dollar units and even that is marginal. (I did use a powerline filter on an old furnace condensate pump but that was because the pump was junk. A new pump solved that problem)
While I can't explain it, I have seen shielding help to a limited degree with 60 cycle hum.

BY the way, 60 Hz is well below the "E" field which means that if you were truly trying to filter an RF signal at 60 hZ, you would be in the "H" field or magnetic field.
It takes ferrous metal to isolate this but not a big deal as the amplitude of the signal drops like a rock with distance.

So you're saying the 60 Hz hum is magnetically induced?
How is this different from the electrostatic noise that can be shielded against?

I've been trying to get my head around this literally for years now, but recently (since I got a bass with single coil pickups) it's more relevant for me.
Humbuckers solve my noise problem at home, with one exception, a Mexican Fender Blacktop. I'm not sure if it was because the humbuckers were overwound or what...

The humbuckers in my SRX (SR eXtreme) & my guitars are nice & quiet, but the noise doesn't seem to be exclusively 60 Hz hum.

I did some experimenting with my Ibanez Premium (with the Big Singles).
First I tried quieting the single coil noise by touching the strings, doesn't work, nor does touching a grounded switch on the bass (this is with only one pickup selected). I did discover that there's 200 Ohms of resistance between my bridge & the output jack, and that the coating on Elixir strings is definitely not conductive. Thoe strings are surprisingly well insulated.
That's another issue that I'm going to try and figure out tomorrow, the 200 Ohms of resistance

At least I know the switches are grounded, because if I have both pickups selected & touch a switch there's definitely a drop in noise.

If I face the bass to the South or North the noise is at its pinnacle, but East or West & it at its minimum. Luckily I play facing East, Feng Shui & all
To try and see if any of the noise is from the power, I disconnected the UPS that feeds my amp from the wall, after I turned off my computer, speakers, & monitor.

Flipped on the amp & tried the same touchy feely stuff, no change. The directional bit still remains the same as well.
Now, it did occur to me that the battery power of the UPS is being inverted to the same 60 Hz that's coming from the wall outlet, so...
how could the noise be directional if it's coming from the power?

The strange thing about running on UPS power was this,
if I put my hand over a pickup, even with both selected, there was extra noise.
It was picking up static electricity from my body, but oddly (& luckily) doesn't do that under normal power.

 

[Jim C]

60 cycle hum can be from the magnetic or H field
An example could be an amp that normally doesn't hum unless it's very close to another amp or wall wart.
This magnetic field interference drops exponentially with distance

I think the majority of single coil noise is due to RFI emanations which can be a harmonic of the power line, or from a variety of sources to include devices in the house.
I thought the UPS was a brilliant idea but now see that they can produce RF in the DC to AC conversion process

Here's one link although not the one I was looking for:
Identifying Sources of Radio Frequency Interference Around the Home

 

[Killed_by_Death]

Yeah, the first time I tried the amp/UPS trick (2015) I put the amp right beside the UPS & the noise was crazy, LOL!
There's probably a decent amount of EMI pouring off that UPS when the battery is discharging.

Today I used the amp at the end of a 12' cord, as far from the UPS as I could get it.
ditto with keeping the instrument away from the UPS

Back when I did this experiment in 2015, I found the noisy spot that I couldn't turn off was where the power cables come in. Even with every device in here off (main breaker off) there was noise along that wall.

In 1994 I had a problem with losing our network connection (UTP) between the upstairs floor & the ground floor. The wire went near a company-wide UPS (big one).
The wire was in a trunk, but still was getting interference.
I solved the problem by getting routers with at least one BNC connector & ran a RG-6 (or 59) coax wire between the two floors.

 

[somebrains]

Yeah, the first time I tried the amp/UPS trick (2015) I put the amp right beside the UPS & the noise was crazy, LOL!
There's probably a decent amount of EMI pouring off that UPS when the battery is discharging.

Today I used the amp at the end of a 12' cord, as far from the UPS as I could get it.
ditto with keeping the instrument away from the UPS

Back when I did this experiment in 2015, I found the noisy spot that I couldn't turn off was where the power cables come in. Even with every device in here off (main breaker off) there was noise along that wall.

In 1994 I had a problem with losing our network connection (UTP) between the upstairs floor & the ground floor. The wire went near a company-wide UPS (big one).
The wire was in a trunk, but still was getting interference.
I solved the problem by getting routers with at least one BNC connector & ran a RG-6 (or 59) coax wire between the two floors.

Lolz, I used to be a VMware architect.
I built out datacenters for an ISP to migrate and upgrade applications.
Imagine how much gear I had running at home to push/pull/test entire application environments.
At one point before I went 100% AWS I was wearing -30db in ear shooting plugs in my home office bc I had an Oracle Cluster running off a UPS from the dryer receptacle.

If you guys want to find out where the runs in your house are, or how noisy everything in your house is, move your amp and bass around every socket.

DirectTV boxes can be particularly noisy.

Easy solution would be to send my gf out for a week and have my house fully rewired.
Nothing like a mix of knob & tube with a subpanel upgrade from the 70's, and random circuits added in the 90's.

Did I mention buying a Furman is a good idea?

 

[Killed_by_Death]

I think I verified that my noise isn't from the power, at least not directly.
Sure it's from the power in a sense of EMI, so why can't shielding block the EMI coming off our devices?
Ah right, it would have to be ferrous, but wouldn't a magnetic interference need to be pretty close to our instrument?

FWIW, I've got both kinds of noise:

One is there even with both pickups engaged, which goes away when I touch the grounded switch

Another that's really noticeable when only one pickup is on, even when touching that grounded switch

Neither is really noticeable with the gain at only 50% or less.

 

[BlueTalon]

Did I mention buying a Furman is a good idea?

You're talking about a power conditioner? What exactly do those things do? Can they help with under-voltage situations?

 

[somebrains]

I think I verified that my noise isn't from the power, at least not directly.
Sure it's from the power in a sense of EMI, so why can't shielding block the EMI coming off our devices?

FWIW, I've got both kinds of noise:

One is there even with both pickups engaged, which goes away when I touch the grounded switch

Another that's really noticeable when only one pickup is on, even when touching that grounded switch

Local 6 guys in SF have meters to test for EMI.
You know anyone at a union shop that can draw tools for you?
We had to do that with tape jukeboxes and cold storage drive arrays.
May not be such a big step to fix.

The pickup deal I would continuity check your circuit.
I would go as far as pulling the grounds and redoing them from the jack thru the pots etc etc.
Shielding is all well and good but sometimes doing a table session on your electronics will pop a couple problems to light.

Sometimes you find a switch that isn't grounded in all positions.
Once in a while you find a wire that needs to be replaced.
Depending on the setup something got twisted with a talkative wire that shouldn't be twisted in or you have to isolate and reroute.

For sure, Big Singles like being surrounded by copper tape.
When i flip my BMs into basically 4 Big Singles in series I found some preamps I'd tried were noisier than others.
I was shielding my preamps FROM interaction with my BMs.
Nothing else was much of a concern.

You wanna try it, I'll send you one of the MEC 2-band preamps I have sitting here.

 

[somebrains]

You're talking about a power conditioner? What exactly do those things do? Can they help with under-voltage situations?

Nothing helps in a brown out besides spending some $$$ for basically a capacitor that pumps you back up to acceptable voltage. In of itself most of what you'll find are UPS that cost a lot and generate a ton of noise.

I have a Zerosurge here for my home workstation, bc knob and tube house wiring.
I have my bass gear running thru it.
Super sucks without it.
A previous employer paid for a pair of them, they aren't cheap.

Furman would just be to deal with crappy bar lighting, bc neon beer signs and amateur electrical upgrades are still a thing.