Using a metal pickguard to reduce pickup noise

[sunbeast]

EDIT: Sorry need to take a closer look at this. A lot of that upper area noise is handling noise - picking up the pickguard etc.

Why I think this not 60-cycle related noise that is being cut by the plate:

The major signal reduction (in the time frame 8 to 11 seconds when the plate is first placed over the pickup in the video), is the yellow stuff above around 3000Hz. That upper area becomes very clear when the cover is in place. The lower "hum" related things persist throughout (lower part of chart).

View attachment 5002331

I really don't hear much harmonics of anything above that frequency in your video at all- I think most of the noise in the video from above the 3K region are just the physical noises of you scraping the plate against the pickguard and other physical disturbances- you can see the peaks represented in the highs here occur right when you rub the two plates together in the video. Here's 3khz for reference: ). I hear instead a semi-reduction in all the midrange harmonics (that I would expect to mostly be multiples of 60hz)- you can see that clear dampening throughout the midrange (everything above 200hz) in the 10-11 second section of your picture where you actually have the plate around the coil.

 

[skycruiser]

I really don't hear much harmonics of anything above that frequency in your video at all- I think most of the noise in the video from above the 3K region are just the physical noises of you scraping the plate against the pickguard and other physical disturbances (Here's 3khz for reference: ). I hear instead a semi-reduction in all the midrange harmonics (that I would expect to mostly be multiples of 60hz)

Right, I noted that in the edit to my post. I'm taking a closer look at the frequencies now. This is a cleaner time period - pickguard cover on and then off, with no noisy shuffling between:

There are several very bright lines that show up in the 2000Hz-3000Hz range, quite far from 60Hz and the few multiples where you might expect the most harmonic content.

I wish I had the ability to to line plots of frequency vs. amplitude. It is difficult to see the relative reduction looking at these color plots. But those bright yellow lines sure jump out at me, and I think it is not possible to determine if they are harmonics of 60Hz without a numerical analysis. Almost any line that far from 60 might look like it could be a harmonic, but without knowing the frequency there's no way to be sure.

 

[sunbeast]

Right, I noted that in the edit to my post. I'm taking a closer look at the frequencies now. This is a cleaner time period - pickguard cover on and then off, with no noisy shuffling between:

There are several very bright lines that show up in the 2000Hz-3000Hz range, quite far from 60Hz and the few multiples where you might expect the most harmonic content.

I wish I had the ability to to line plots of frequency vs. amplitude. It is difficult to see the relative reduction looking at these color plots. But those bright yellow lines sure jump out at me, and I think it is not possible to determine if they are harmonics of 60Hz without a numerical analysis. Almost any line that far from 60 might look like it could be a harmonic, but without knowing the frequency there's no way to be sure.

View attachment 5002384

You can definitely see (and hear) the greatest reduction happening in the midrange harmonics above that 200hz-ish line area in your picture (perhaps with a thicker plate of the same material it might extend a bit lower and have a larger amplitude reduction as well). I'd expect if this plate was also grounded then you might see a larger reduction in some of that higher frequency noise too (though it is that midrange noise that is the most audible to our ears anyway- and where it most interferes with musical frequencies- unless there is a particularly bad radio-frequency interference source present)

 

[bassdude51]

What is the blue plate thing? Aluminium plate covered with tape?
Why is the aluminium pickguard doing something, but not the aluminium foil? Is it only aluminium?
Since the pickguard is not grounded, why is the noise still attenuated? Is the EM noise simply "reflected" back or something like that?
Would the noise have been reduced further had the pickguard been grounded?
Do you get better noise reduction by placing another plate under the pickup?

Exactly! Great questions asked!!!!!!!!!! ^^^^^
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I didn't watch the video but here come the "buts".

Jazz Basses' 2 pickups are reversed wound/revered polarity. Run together at full volume, they act as a humbucker. Pickups run separately, there will be single coil hum. Use the tone pot to off some of the high end. Hum will hardly be heard.

Old 60s P Basses (don't know about the Js) had an thin aluminum plate under the pickguards which would have done the same thing as an anodized aluminum guard. (P Basses are humbuckers and hum is not an issue.)

BUT.............if the aluminum guard or plate is not grounded to the pots/jack, it doesn't act as a "hum" shield. So, this guard in the video is not shielding anything.

If copper tape is taped inside the pickup cavity, electronics cavity, underside of the guard and it is grounded to the pots/jack, this would be your best shield.

As for hum, turn the tone pot down a hair and most if not all of the single coil hum will not be heard.

And if hum is an issue, humbuckers!

I personally love the sound of single coils! Clearer and better definition.

 

[skycruiser]

Exactly! Great questions asked!!!!!!!!!! ^^^^^
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I didn't watch the video but here come the "buts".

Jazz Basses' 2 pickups are reversed wound/revered polarity. Run together at full volume, they act as a humbucker. Pickups run separately, there will be single coil hum. Use the tone pot to off some of the high end. Hum will hardly be heard.

Old 60s P Basses (don't know about the Js) had an thin aluminum plate under the pickguards which would have done the same thing as an anodized aluminum guard. (P Basses are humbuckers and hum is not an issue.)

BUT.............if the aluminum guard or plate is not grounded to the pots/jack, it doesn't act as a "hum" shield. So, this guard in the video is not shielding anything.

If copper tape is taped inside the pickup cavity, electronics cavity, underside of the guard and it is grounded to the pots/jack, this would be your best shield.

As for hum, turn the tone pot down a hair and most if not all of the single coil hum will not be heard.

And if hum is an issue, humbuckers!

I personally love the sound of single coils! Clearer and better definition.

Try watching the video and then retract the statement about the pickguard not doing anything. This is basically a "one variable" demo.

 

[sunbeast]

I will try this tonight and see if it has a similar effect. The thickest wire I have is 14 or maybe 12-gauge single copper - basically house electrical wiring type of wire. How thick do you think is needed to have this effect?

I believe @totalnoob is talking about the eddy current effect of a copper plate surrounding the pickup coil, but not the shielding effects- basically describing the effects shown in that document I posted earlier where he measures the effects of copper rings of different gauges placed around pickup coils on the frequency response of the pickup.

 

[bassdude51]

Try watching the video and then retract the statement about the pickguard not doing anything. This is basically a "one variable" demo.

Yes, I should have watched the video, my bad. ADD issues, plus I have built (doesn't make me expert) over 30 bass guitars and have experienced and messed with 60 cycle hum, single coils and humbuckers and shielding. I don't get very bothered with 60 cycle hum. The Fender Telecaster and Strat are my favorite guitars. They hum. Listen to Hendrix live recordings when the stage is quiet. Buzzzzzzzz.

OK, I watched the video.

First off, hum is reduced when the aluminum guard is over the pickup but hum can still be heard. Also, when we play bass, normally our hands are touching the strings which greatly reduces hum as there is a degree of grounding.

In the video, here are no strings and the pickup is isolated by itself. Loosing the human hands to the string grounding effect.

Interesting video. Thanks for sharing.

Single coils = hum. Humbuckers = quiet. A fact of life.

 

[totalnoob]

Something to try though is to cut a notch all the way through your copper plate

This is a very valuable experiment to make, and it will yield immediate results.

 

[skycruiser]

OK, so I destroyed my precious copper plate "for science".

I tried a few things and would be happy to try anything that anyone suggests to help understand what is going on (within reason).

• Pickup is in a plastic bag so I won't short it out
  
• The red cable is connected to the ground side of the output jack. At the start I touch the hot side to show it is grounded (output goes silent).
• Show grounding the plate does not audibly affect anything
• Show adding 2 plates together does not audibly affect anything
• Wrapped the pickup in foil - no noise reduction
• Ground the foil - no noise reduction
• Put a pickguard plate over the foil wrapped pickup. Actually to my ears the noise is higher than the pickup alone with the pickguard
• Put the copper plate on and cut it (killing the noise reduction effect)
• Put the pickguard over the cut plate, noise is reduced

So yes a continuous conductor ring around the pickup is required. Or a continuous, solid plate over or under seems to do the trick, so it serves as a loop around, I guess.

Edit: Just checked - simply shorting across the cut in the copper plate doesn't fix it. I tried crossing the gap with foil and it is still noisy. But if I push the plate so the two cut ends are in contact, the noise goes down. Maybe not as well as it was originally, but more than shorting across with foil.

So I'll be off to Lowes to buy another $10 copper plate...

 

[sunbeast]

OK, so I destroyed my precious copper plate "for science".

I tried a few things and would be happy to try anything that anyone suggests to help understand what is going on (within reason).

• Pickup is in a plastic bag so I won't short it out
  
• The red cable is connected to the ground side of the output jack. At the start I touch the hot side to show it is grounded (output goes silent).
• Show grounding the plate does not audibly affect anything
• Show adding 2 plates together does not audibly affect anything
• Wrapped the pickup in foil - no noise reduction
• Ground the foil - no noise reduction
• Put a pickguard plate over the foil wrapped pickup. Actually to my ears the noise is higher than the pickup alone with the pickguard
• Put the copper plate on and cut it (killing the noise reduction effect)
• Put the pickguard over the cut plate, noise is reduced

So yes a continuous conductor ring around the pickup is required. Or a continuous, solid plate over or under seems to do the trick, so it serves as a loop around, I guess.

Edit: Just checked - simply shorting across the cut in the copper plate doesn't fix it. I tried crossing the gap with foil and it is still noisy. But if I push the plate so the two cut ends are in contact, the noise goes down. Maybe not as well as it was originally, but more than shorting across with foil.

So I'll be off to Lowes to buy another $10 copper plate...

Given there wasn't much high-frequency noise to begin with (it sounds almost completely like mains hum to me), I'm not super surprised there is little to no audible difference there but I would also test the surface of the aluminum pickguard with a multimeter to insure it is actually conductive (otherwise the grounding connection isn't actually grounding the plate)- sometimes there might be finish or plating that would interrupt this.

I wasn't sure what the effect of cutting the plate would have on the shielding effect, which is why I called it an "experiment", but I commend you for following through! It seems that the same continuity necessary for eddy currents is also necessary for this shielding effect- that makes some sense as a link posted earlier in this thread by another TB'er suggested this shielding effect was actually a result of eddy currents induced in the metal from the interference waves (I guess eddy currents themselves act as the shielding effect by dissipating the strength of the interference much as they dissipate the strength of the pickup). That is admittedly beyond my knowledge base though!

 

[Dadum]

27323366[/URL], member: 337344"]OK, so I destroyed my precious copper plate "for science".

I tried a few things and would be happy to try anything that anyone suggests to help understand what is going on (within reason).

• Pickup is in a plastic bag so I won't short it out
  
• The red cable is connected to the ground side of the output jack. At the start I touch the hot side to show it is grounded (output goes silent).
• Show grounding the plate does not audibly affect anything
• Show adding 2 plates together does not audibly affect anything
• Wrapped the pickup in foil - no noise reduction
• Ground the foil - no noise reduction
• Put a pickguard plate over the foil wrapped pickup. Actually to my ears the noise is higher than the pickup alone with the pickguard
• Put the copper plate on and cut it (killing the noise reduction effect)
• Put the pickguard over the cut plate, noise is reduced

So yes a continuous conductor ring around the pickup is required. Or a continuous, solid plate over or under seems to do the trick, so it serves as a loop around, I guess.

Edit: Just checked - simply shorting across the cut in the copper plate doesn't fix it. I tried crossing the gap with foil and it is still noisy. But if I push the plate so the two cut ends are in contact, the noise goes down. Maybe not as well as it was originally, but more than shorting across with foil.

So I'll be off to Lowes to buy another $10 copper plate...

Great experiment!

If you stick the pickup wrapped in plastic inside of the cardboard tube of aluminum foil (if it fits), is there any noise reduction?

 

[skycruiser]

Given there wasn't much high-frequency noise to begin with (it sounds almost completely like mains hum to me), I'm not super surprised there is little to no audible difference there but I would also test the surface of the aluminum pickguard with a multimeter to insure it is actually conductive (otherwise the grounding connection isn't actually grounding the plate)- sometimes there might be finish or plating that would interrupt this.

I wasn't sure what the effect of cutting the plate would have on the shielding effect, which is why I called it an "experiment", but I commend you for following through! It seems that the same continuity necessary for eddy currents is also necessary for this shielding effect- that makes some sense as a link posted earlier in this thread by another TB'er suggested this shielding effect was actually a result of eddy currents induced in the metal from the interference waves (I guess eddy currents themselves act as the shielding effect by dissipating the strength of the interference much as they dissipate the strength of the pickup). That is admittedly beyond my knowledge base though!

Good point about the metal surface. It is anodized which is an insulator. I just tested again, this time making contact with an exposed spot in one of the screw holes. Properly grounding the pickguard does cause it to slightly further reduce the noise and changes the character of the noise a little, but it is not a significant difference. It is enough of a difference that if I planned to implement this in a bass for noise reduction, I would make the effort to try to ground the plate as well.

@Dadum - putting the pickup inside the foil roll provides similar noise reduction to the aluminum pickguard and the copper plate. This is a fairly hefty roll of aluminum foil so there is a lot of metal there.

Also not shown in the video, I just made a loop of 12-gauge copper wire, around 5 or 6 turns twisted together. If I place it around the pickup in the same orientation as the pickguard, it reduces the noise a similar amount. If I rotate it other directions it does not reduce the noise. So clearly this thick metal piece has to encircle the pickup coil, approximately. (Apparently just setting the pickup on the plate is close enough.)

So I feel I've leaned some things that should not be done but don't have much clarity on why this plate does anything at all. I also plan to do some close listening test so see if I can detect any changes in tone with and without the plate. I'll have to do this with my Jazz bass after I buy and cut another copper plate.

 

[totalnoob]

Also not shown in the video, I just made a loop of 12-gauge copper wire, around 5 or 6 turns twisted together. If I place it around the pickup in the same orientation as the pickguard, it reduces the noise a similar amount. If I rotate it other directions it does not reduce the noise. So clearly this thick metal piece has to encircle the pickup coil, approximately.

This proves conclusively that the metal pickguard works as a transformer secondary, shorted. And I think what's happening is a filter effect - you are filtering out some components of the signal, be that noise or otherwise. I think this shows that you are in fact altering the frequency response of your pickup. Whether that's an effect you like or not, it's up to you to decide.

Something interesting to consider is that what you're doing is probably no better than just reducing the mids and trebles at the amp.

 

[skycruiser]

I picked up a new copper plate and will craft a new shield. I'll try to do some recording with and without to see if the claim about this significantly affecting the response of the pickup is true. In my experience so far, it does not have a noticeable effect on the sound of the pickup.

 

[rwkeating]

If the copper plate and pickup are held together as a unit and turned at a right angle, does the noise change? Does the noise change at any other angle?

 

[skycruiser]

If the copper plate and pickup are held together as a unit and turned at a right angle, does the noise change? Does the noise change at any other angle?

The noise is highly sensitive to pickup orientation. Before I found this fix with the metal plate, I would always orient my guitar north-south when recording since that results in the lowest noise level in my music room. The metal plate is effective in all orientations.

 

[Mr Low End]

I have a question regarding this topic. I just purchased an anodized gold guard for my Fender American Pro ll P. I also purchased a new set of Fender pure vintage 63’s to drop in when I change the guard. Since I’m putting the new anodized guard on do I need to do anything special to it before installing it? Do you recommend putting something protective on the bottom of the guard to protect the bass?
Thanks for the replies and help.