Shielding - How do you know it will help?

[Killed_by_Death]

You know anyone at a union shop that can draw tools for you?

No, but I know some dudes who are tools

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

Thanks for the offer,
Ibanez boast that their preamp in this bass is quiet, which I think is the saving grace. I'm quite sure the humbuckers in my Mexican Fender Blacktop were noisier than this bass, before I shielded the Blacktop.
It's also a very specific preamp, with a switch to change the frequencies of the mid control.

Hmm, now I'm looking for where I saw Ibanez advertize that this preamp is quiet, but can't find it

 

[somebrains]

My buddy's parents live in the Oakland Hills. Their garage is my favorite place to play bc the entire district they live in is brand new. It all burned down multiples times. Power is so good, there's no appreciable interference. Everything sounds so good. I swear my amps are louder and cleaner there.

So many factors contribute to issues, I just visit that garage every so often to jam.
It's like going to a good recording studio without the $$$.

 

[Killed_by_Death]

Same applies to my parents' home, very rural & no noise!
I took my rig out there in 2015 & it was dead quiet.

 

[somebrains]

Do they have good power with not much on the circuit?
You notice stuff like that.
Like your amps decided to eat their Wheaties, pump out 50 up downs, and hit the 100yd until they shaved the time down.

 

[Killed_by_Death]

There are rather large power stanchions nearby & the biggest draw on their power is the heat pump:

I installed the satellite TV dish for a guy just up the road who lives almost directly under the stanchions & he was saying they got weird interference from them.
Luckily I didn't need to aim his dish toward those wires, LOL!

 

[somebrains]

There you go, grab a pignose or some such and walk out there with your bass and a gas soldering set.

Find a spot where it's bad, go to town on your bass.

 

[Rockin John]

The use of a UPS - Uninteruptable Power Supply - only has value for the input and output line filtering. As a piece of equipment it’s purpose is to mantain mains power to sensitive equipment. Eg, to a computer to give it enough time to save files before the maine power collapses completely.

To achieve this, the UPS uses an inverter to artificially recreate the line supply. Inverters are very dirty / noisy electrically because they employ high current, very fast switching spikes which introduce EMI into nearby electrical systems, both through the the air and through cables. How much noise they introduce will be governed by many factors, not least of which will be the distance between the UPS and other equipment (like an electric bass).

I have to admit that it’s a good 15 years since I had anything to do with a UPS, so many improvements in their design may have taken place to quieten them down a little! However, a UPS is the last thing I would use for / near music amplification gear. A relatively simple, passive power line filter of good design should keep all the power line noise out of the amps.

These things are usually built around a common mode choke (of sufficient current carrying capacity), fast capacitors and Transorb style suppressors. They can be purchased, but are not difficult to make: they need to be constructed according to electrical regulations by a competent person to avoid electric shock hazard.

 

[Rockin John]

Google, Power Line Conditioner for ideas of ready made units, or Power Line Conditioner schematic if you want to make one.

 

[Killed_by_Death]

I plug my amp into the UPS purely out of convenience, otherwise I would need to unplug a lamp every time I turned on my amp.
Doesn't the UPS have a power line conditioner?

The noise I'm getting is directional, so I don't believe it is from the power, at least not directly.
If I face my bass East or West, the noise all but goes away.

I mentioned a case earlier of a member who was having noise with humbuckers that didn't go away when touching strings, and in that experiment a battery powered amp was used (not a regular amp on a UPS) while all the devices in the home were turned off, still noisy & still directional.
I had the same thing with my humbucker-equipped bass in 2015 & did the same experiment, only I was using my amp at the end of a 12' cord on the UPS.

 

[Old Garage-Bander]

Convert your practice room into a Faraday cage and connect all electrical grounds to a huge steel spike in the lawn out back?

Ah. Nothing warms my heart like a nice copper clad, steel ground rod, or four.
Don't use those little whimpy 4 ft ones either. Go for the 10 footers.
Get them out away from the backfill around your foundation.
It's also nice to live in a part of the country that has good soil. If you don't, you need to water your rods more often.

 

[Rockin John]

'
"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.

If this helps .....
ElectroMagnetic Interference is the general term given to noise. Radio Frequency Interference - RFI - is EMI because radio waves are electromagnetic waves: by convention, radio waves start at around 60KHz ... which is about three times the top limit of human hearing. Radio frequencies carry on getting higher and higher up to the limit of current technology. Fortunately, RFI is increasingly easy to get rid of in audio circuits by shielding and other techniques.

60Hz Power Line hum (50Hz in UK) is also EMI because the waves are electromagnetic in nature. They permeate the air so can be picked up by anything that’ll act as a suitable receiver. Ie. A single coil bass pickup. (Humbuckers also pick up the 60Hz - and any other noise frequencies - but, of course, they buck the hum!).

The difference between electromagnetics and electrostatics is marked. Electrostatics features a steady state electrical potential with no magnetic component whereas electromagnetics features a potential that **changes with time**. That makes a huge difference in the way screening is accomplished and it is frequency dependent, too. So what works for RFI, won’t work for 60Hz.

It’s not possible to effectively shield a pickup against the frequencies of a bass (which includes the power line frequency, unfortunately) because the strings have to alter the pickup’s magnetic field to generate an output. The technical term for that is variable reluctance (so a guitar pickup is technically known as a variable reluctance generator).

All told this is a massively complex subject and I don’t know of a layman’s guide.

 

[Old Garage-Bander]

So if the noise doesn't go away by touching the strings (with a grounded bridge) then shielding won't help?

I think you really need to look at noise reduction as a multi-pronged attack.
There is no one solution that fixes everything, because the causes of hum and or noise come from varied sources and happen for different reasons.

What helps with one kind of noise at one venue might do nothing for a different form of noise at a different location.
It's best to take all of the precautions and cover all the bases as best as possible.

Some folks tend to lump all unwanted "noise" into one category. Then they don't understand why putting in all of that shielding did nothing to fix their problem. It helps to understand the different types of unwanted audio that can get into your system. It also can be a life's long learning process to understand, analyze, and then fix noise.

I use the term noise rather than hum, generically because hum is only one type of noise. I define noise as any unwanted audio that detracts from the desired audio. Hum is one of many specifically defined sources of noise. If I've determined that the noise is hum, that helps to narrow down the possible solutions.

But taking all of the precautions, regardless of what happens to be bothering you today, is usually the best course of action.

 

[Killed_by_Death]

So what works for RFI, won’t work for 60Hz.

This is the one I'm having difficulty with. Is it because there's more of a magnetic component to the interference?
or is it simply because of the frequency?, which of course every electrical device is powered from

All told this is a massively complex subject and I don’t know of a layman’s guide.

I did fairly well in Electricity & Electronics classes & graduated with a 97.5% average, but that was a long time ago & we didn't really go into detail about EMI.
Induction was covered in pretty good detail, though. (motors & generators)

I've been trying to avoid using the term RFI due to the radio frequencies being so much higher than the noise we're dealing with, but it still comes in as waves through the air.
otherwise changing the orientation of the instrument would have no effect on the noise (if it were coming in directly from the power there's be no change, right?)

 

[Old Garage-Bander]

This is the one I'm having difficulty with. Is it because there's more of a magnetic component to the interference?
or is it simply because of the frequency?, which of course every electrical device is powered from




I did fairly well in Electricity & Electronics classes & graduated with a 97.5% average, but that was a long time ago & we didn't really go into detail about EMI.
Induction was covered in pretty good detail, though. (motors & generators)

I've been trying to avoid using the term RFI due to the radio frequencies being so much higher than the noise we're dealing with, but it still comes in as waves through the air.
otherwise changing the orientation of the instrument would have no effect on the noise (if it were coming in directly from the power there's be no change, right?)

RFI... yet another source of noise.
Especially if you have high levels of amplitude modulated signal, aka AM Radio or another noise source that has an amplitude varying component to it nearby. Some components, and some faulty wiring can act as a diode and rectify the signal. In extream cases you might even hear a radio station.

Diodes are the original AM detector. In the early days they could be nothing more than a junction if dissimilar metals with impurities. A poor solder joint, or a corroded contact at the right place in a circuit can be affected by these signals. An active bass, could be subject to this even more so than a passive. If it takes on an unwanted signal that gets detected to some audio level early on in the active circuitry, it could be amplified further before leaving the instrument.

 

[Rockin John]

This is the one I'm having difficulty with. Is it because there's more of a magnetic component to the interference?
or is it simply because of the frequency?, which of course every electrical device is powered from




I did fairly well in Electricity & Electronics classes & graduated with a 97.5% average, but that was a long time ago & we didn't really go into detail about EMI.
Induction was covered in pretty good detail, though. (motors & generators)

I've been trying to avoid using the term RFI due to the radio frequencies being so much higher than the noise we're dealing with, but it still comes in as waves through the air.
otherwise changing the orientation of the instrument would have no effect on the noise (if it were coming in directly from the power there's be no change, right?)

RFI... yet another source of noise.
Especially if you have high levels of amplitude modulated signal, aka AM Radio or another noise source that has an amplitude varying component to it nearby. Some components, and some faulty wiring can act as a diode and rectify the signal. In extream cases you might even hear a radio station.

Diodes are the original AM detector. In the early days they could be nothing more than a junction if dissimilar metals with impurities. A poor solder joint, or a corroded contact at the right place in a circuit can be affected by these signals. An active bass, could be subject to this even more so than a passive. If it takes on an unwanted signal that gets detected to some audio level early on in the active circuitry, it could be amplified further before leaving the instrument.

It’s why you’ll often see a small capacitor across the Base/Emitter junction of a bipolar transistor... because it’s a pn or np junction that is a diode and can rectify incoming modulated RF.

 

[Rockin John]

This is the one I'm having difficulty with. Is it because there's more of a magnetic component to the interference?
or is it simply because of the frequency?, which of course every electrical device is powered from




I did fairly well in Electricity & Electronics classes & graduated with a 97.5% average, but that was a long time ago & we didn't really go into detail about EMI.
Induction was covered in pretty good detail, though. (motors & generators)

I've been trying to avoid using the term RFI due to the radio frequencies being so much higher than the noise we're dealing with, but it still comes in as waves through the air.
otherwise changing the orientation of the instrument would have no effect on the noise (if it were coming in directly from the power there's be no change, right?)

An electromagnetic AC wave has an electrical component and a magnetic component. These two change with time, together. Noise from you bass works by electromagnetic induction - just like an electrical transformer - but, in this case, there is an air gap between your bass and the source of the interfering noise. As you correctly say, you can tell it’s disceminating through the air by moving your bass and hearing the sound change accordingly. (The loudness of the noise is directly proportional to the rate of change of magnetic flux ... which is why hard string-plucks and fast moving spikes of interference sound the loudest).

As a side issue, some time ago I designed some pickups as an experiment. Each string had its own small coil - a few hundred turns on a sewing machine shuttle - it’s own magnet and it’s own little amplifier to make up for the lack of turns of wire. I built both discrete amps and op-amp amplifiers as part of the experiment. They were single coil, active pickups I suppose, with no hum cancelling circuitry. The strings weren’t earthed at all. Our band rehearsed in a room lit by fluorescent lights. The guitarists with their humbuckers were terribly plagued by the lights: my bass was totally silent.... until I played it, that is!! Quiet pickups are possible.

 

[somebrains]

So none of you guys have played in a dive bar that thinks defective neon signs are mood lighting?
You can 100% setup a bass with EMGs with shielded cavities and still hear the flickering Corona sign or ancient keg cooler. You are still connected to an amp or or something. It really prompted a lot of guys to try DI when they could. Since the 70's people have wanted to run XLRs ala Alembic.

Strings or pots becoming antennas is just bad, and it happens.

I once had a guy come into the shop that was recording at Record Plant Sausalito who was also gigging around the Bay Area to PR the new record have us throw a set of EMGs and do a full shielding job. He was fine with his player in the studio, but he learned why so many Bay Area players used EMGs bc most of the venues in the 90's were horrible to play in. A couple notable metal spots are line of sight within a couple blocks of PG&E switching stations.

 

[Jim C]

I knew a tech at the old Media Sound in NY.
The studio opened one morning and there was noise in the mic pre's of the consoles.
So bad that sessions were cancelled.
They had 3 really sharp techs working on it for 2 days.
Turned out to be a noisy motor in a escalator that just got noisy after being in service for a long time.

A few sharp EE's on this board have said that any new decent amp has sufficient power line filtering built in and that something like a Furman is not going to clean up the power line noise.

There are UPS units that will maintain constant output voltage even with a low line voltage.
These auto transformers draw more current to generate the high voltage.

I have never been worried about brown outs with MI gear as I've never seen one hurt by low voltage; perhaps I've just been lucky. Not sure what voltage you would set it to before power shut down.
I can say for sure that Dolby A units will not work below 109 volts; don't ask me why I know this...

 

[Rockin John]

No, but I know some dudes who are tools




Thanks for the offer,
Ibanez boast that their preamp in this bass is quiet, which I think is the saving grace. I'm quite sure the humbuckers in my Mexican Fender Blacktop were noisier than this bass, before I shielded the Blacktop.
It's also a very specific preamp, with a switch to change the frequencies of the mid control.

Hmm, now I'm looking for where I saw Ibanez advertize that this preamp is quiet, but can't find it

Every onboard preamp should be quiet if correctly designed. There are plenty of companies producing super-quiet op amps these days (my preference is Analogue Devices’ chips, but there are others) so there’s no excuse for noisy on-boards. Decent passive components - resistors and capacitors - help keep the noise down. Some chips are very low current, too, so that battery life can be extended far beyond what it would have been just a few years ago.

 

[Rockin John]

So none of you guys have played in a dive bar that thinks defective neon signs are mood lighting?
You can 100% setup a bass with EMGs with shielded cavities and still hear the flickering Corona sign or ancient keg cooler. You are still connected to an amp or or something. It really prompted a lot of guys to try DI when they could. Since the 70's people have wanted to run XLRs ala Alembic.

Strings or pots becoming antennas is just bad, and it happens.

I once had a guy come into the shop that was recording at Record Plant Sausalito who was also gigging around the Bay Area to PR the new record have us throw a set of EMGs and do a full shielding job. He was fine with his player in the studio, but he learned why so many Bay Area players used EMGs bc most of the venues in the 90's were horrible to play in. A couple notable metal spots are line of sight within a couple blocks of PG&E switching stations.

So none of you guys have played in a dive bar that thinks defective neon signs are mood lighting?
You can 100% setup a bass with EMGs with shielded cavities and still hear the flickering Corona sign or ancient keg cooler. You are still connected to an amp or or something. It really prompted a lot of guys to try DI when they could. Since the 70's people have wanted to run XLRs ala Alembic.

Strings or pots becoming antennas is just bad, and it happens.

I once had a guy come into the shop that was recording at Record Plant Sausalito who was also gigging around the Bay Area to PR the new record have us throw a set of EMGs and do a full shielding job. He was fine with his player in the studio, but he learned why so many Bay Area players used EMGs bc most of the venues in the 90's were horrible to play in. A couple notable metal spots are line of sight within a couple blocks of PG&E switching stations.

Any gas discharge device has the potential to create electrical noise ... neon signs and fluorescent lights are both gas discharge devices. They work on the principle of ironising a gas to form a plasma. The plasma can only be created by a pretty high voltage (spike) but, once running, the device operates at a much lower voltage relative to the initial spike. Each time the lamp is required to run it needs another spike. As neon signs are required to flash on and off there are lots of electrical spikes filling the air, all ready and waiting to be picked up by the nearest bass (then amplified). Copper foil should help but will not be the whole solution.

I have personally experimented with Common Mode Transformers as a means of keeping noise from the inputs of onboard preamps, repeating the same thing at the jack socket of the bass. It does work, but how well I do not know as I stopped the experiments.