Summoning Elite Troubleshooters

[dwizum]

In a sense it's proof that a dummy coil can work - but it's not proof that a dummy coil will always work or that a dummy coil will always work well. Dummy coils are usually designed to try to mimic the sensing coil as closely as possible - that way, they create equal but opposite signals from the noise they pick up, and it cancels. Humbuckers are already highly optimized in that the two coils are (usually) identical, in the same orientation, and right next to each other. So the signal they generate on account of noise is pretty much the same and it cancels itself cleanly. Humbuckers are like the perfect dummy coil, factory-matched and in tune.

The way he's buffering the signal from the dummy coil antenna lets you adjust the noise control on the pedal to accommodate for differences between what the dummy coil antenna picks up and what the instrument picks up. It's kind of like an adjustable dummy coil you can tune to account for the total noise. Meanwhile, a dummy coil is a passive "shot in the dark" in that it's not adjustable and just sort of hacks off X amount of Y noise. A humbucker will essentially always be as good or better than a dummy coil unless it's deliberately poorly designed. In my experience, people often chase dummy coils in the belief that single coil pickups have magic tone that can't be duplicated with humbuckers, which isn't really as significant as it's made out to be - it's just accepted as a big deal because most humbuckers have very different formats than most single coil pickups, and those format differences create different tones - but people generalize that the difference in tone is because of humbucker vs. single coil because that's the more obvious or recognizable difference. But we're getting off track now.

I suspect that there are issues with that pedal design which aren't apparent in the video. For instance, imagine you're about to play an important gig, so you tune the pedal to account for the noise created when you're standing at your normal position on stage. But then you walk across stage to kick the drummer out of the band, and the bass picks up a different amount of noise over on that side of the stage - you're going to get an ambiguous result from the pedal unless you get someone to sit there and fiddle with the knob while you're off doing important business firing the drummer. Maybe it's more noisy, maybe it's less noisy, who knows?

 

[fig]

@Crosscheck67, sorry to hear the full shielding didn't make a difference. The job itself is excellent.

Since you have a full shield install (always a good thing) that'll be in place no matter your future plans, and considering the formidable EMI area, did you do a final shield quality check?

Specifically, two things. That all copper strips are electrically connected together to act as one sheet of copper. And also that the components are electrically isolated from the shield.

I'm aware you physically isolated the individual components from the shield with tape, but did you electrically verify?

If not, I have a super easy, barely inconvenient way to check both concerns.

If you already have, then I just wasted internet space LOL.

 

[BlueTalon]

@Crosscheck67, sorry to hear the full shielding didn't make a difference. The job itself is excellent.

Since you have a full shield install (always a good thing) that'll be in place no matter your future plans, and considering the formidable EMI area, did you do a final shield quality check?

Specifically, two things. That all copper strips are electrically connected together to act as one sheet of copper. And also that the components are electrically isolated from the shield.

I'm aware you physically isolated the individual components from the shield with tape, but did you electrically verify?

If not, I have a super easy, barely inconvenient way to check both concerns.

If you already have, then I just wasted internet space LOL.

Looking at his pictures, I'm confident his shielding is all connected to itself. He even took the trouble to put copper tubing in the wire channels, solder the ends of the tubes to the surrounding shielding, and then solder jumper wires connecting the shielding of the pickup cavities to the control cavity. That type of redundancy is super-overkill, but I like it anyway.

 

[fig]

Looking at his pictures, I'm confident his shielding is all connected to itself. He even took the trouble to put copper tubing in the wire channels, solder the ends of the tubes to the surrounding shielding, and then solder jumper wires connecting the shielding of the pickup cavities to the control cavity. That type of redundancy is super-overkill, but I like it anyway.

Yeah, I really like it, too. He really thought it out nicely. I just know me and I wouldn't relax until I electrically verified it. Just me being all anal, I suppose LOL.

 

[BlueTalon]

Yeah, I really like it, too. He really thought it out nicely. I just know me and I wouldn't relax until I electrically verified it. Just me being all anal, I suppose LOL.

In his situation, he doesn't have the option of not being anal.

 

[bdplaid]

In the crevices of my brain, I recall a discussion about whether or not pickup magnets should be grounded. This is more an issue with pickups on which the player can touch the magnet, but I wanted to throw it out there because I recall seeing the 96 art pickups looked like their magnetic poles were grounded.

 

[Crosscheck67]

Sorry I went dark there for a few days. This failure on top of other life stressors (death threats on my windshield from a crazy neighbor the cops talk to but never arrest) literally made me forget about checking in with you guys. I swear to god I'm an EMG pickup and stress is EMI.

 

[JKos]

Everything you say tells me you need to move.

 

[bdplaid]

Everything you say tells you need to move.

This.

 

[BlueTalon]

Sorry I went dark there for a few days. This failure on top of other life stressors (death threats on my windshield from a crazy neighbor the cops talk to but never arrest) literally made me forget about checking in with you guys. I swear to god I'm an EMG pickup and stress is EMI.

Priorities.

You might consider getting a webcam and keeping it pointed at your car.

 

[dwizum]

Wow @Crosscheck67 it sounds like you've had a rough couple days!

In the crevices of my brain, I recall a discussion about whether or not pickup magnets should be grounded. This is more an issue with pickups on which the player can touch the magnet, but I wanted to throw it out there because I recall seeing the 96 art pickups looked like their magnetic poles were grounded.

Here's a good read on the subject:

Audere Audio Pole Piece Noise FAQ

Grounding the magnets gives you some flexibility with other elements of the pickup design since it can address noise caused when the player touches the magnets regardless of the wind orientation or bobbin style. It's also just plain convenient to ground them if you're shielding the pickup with copper anyways (as in that 96 art design, or most Nordstand pickups, which are very similar).

 

[Crosscheck67]

@Crosscheck67, sorry to hear the full shielding didn't make a difference. The job itself is excellent.

Since you have a full shield install (always a good thing) that'll be in place no matter your future plans, and considering the formidable EMI area, did you do a final shield quality check?

Specifically, two things. That all copper strips are electrically connected together to act as one sheet of copper. And also that the components are electrically isolated from the shield.

I'm aware you physically isolated the individual components from the shield with tape, but did you electrically verify?

If not, I have a super easy, barely inconvenient way to check both concerns.

If you already have, then I just wasted internet space LOL.

I'll be checking the ground continuity, because at this point, why the hell not. Fun fact: I have the same multimeter as the one sitting on the floor in the video @bdplaid shared.

Priorities.

You might consider getting a webcam and keeping it pointed at your car.

Already have the Eufy system picked out. But...cams...pickups...cams...pickups...I sort of feel like I owe you guys some damn closure at this point.

Wow @Crosscheck67 it sounds like you've had a rough couple days!



Here's a good read on the subject:

Audere Audio Pole Piece Noise FAQ

Grounding the magnets gives you some flexibility with other elements of the pickup design since it can address noise caused when the player touches the magnets regardless of the wind orientation or bobbin style. It's also just plain convenient to ground them if you're shielding the pickup with copper anyways (as in that 96 art design, or most Nordstand pickups, which are very similar).

How does one ground the magnets? Aren't they isolated inside the pickup?

@bdplaid I'm still fascinated by that blue adjustable hum canceller/filter. Is there a process/filtering difference between that and the Hum Debugger?

 

[BlueTalon]

Already have the Eufy system picked out. But...cams...pickups...cams...pickups...I sort of feel like I owe you guys some damn closure at this point.

You take care of you. We can wait. I'd actually feel like crap if you lost the windshield to your car because you didn't take preventative action against your crazy neighbor because you were concentrating on your bass more because of us.

 

[bdplaid]

How does one ground the magnets? Aren't they isolated inside the pickup?

Some are some aren't. Usually if you see a piece of copper tape on the bottom, it means the coils are grounded. Note that the foil needs to go to ground, not to the negative pole of the circuit.

@bdplaid I'm still fascinated by that blue adjustable hum canceller/filter. Is there a process/filtering difference between that and the Hum Debugger?

Someone posted what I think is a good analysis of that device, I refer you to "circle back" to that.

 

[bdplaid]

And pole grounding : if you have pickups where you can see the poles on the bottom of the pickup, you can put a piece of copper tape on it, the connect a piece of wire to that, and the other end to the shielding.

 

[dwizum]

How does one ground the magnets? Aren't they isolated inside the pickup?

Pickup magnets are (typically) isolated from the coil winding by insulating tape wrapped over the slugs before the pickup is wound. Or, in some designs with a solid plastic bobbin, the slugs are pushed into holes through the core and there's plastic between the slug and the wire. At any rate, pretty much all pickups have the magnets insulated from the coil wire. if you check resistance from the coil to the magnets, you'll get an open circuit.

That leaves the magnets "floating" from a voltage perspective- they're not connected to anything and not part of the circuit. There is a danger associated with that in terms of noise, especially with designs where the magnets are exposed on the tops of the pickups, as is the case in traditional Fender designs. For one thing, the magnets are exposed to any noise that's radiating the pickups. They act like little antenna repeaters and radiate that noise right in the middle of the coil. In designs where there's only a thin layer of tape around the magnets (as in a Fender design where the bobbin is formed from flatwork pressed onto rods), the coil wire will be very closely coupled with the inner few hundred windings just because they're so physically close. Coils are wound such that the wire stacks up and builds thickness as it's wrapped on to the bobbin, so one en of the coil is naturally towards the middle of the pickup and the other end is naturally towards the outside. If the wire is wrapped such that the inner windings are on the "hot" end of the coil circuit, they will be very noisy.

The second noise risk of a pickup with floating magnets is contact with a human. If you are not grounded (i.e. not touching grounded metal on the bass) and you touch an exposed magnet, you turn the magnet into a tiny little antenna sending out a signal from all the noise your (very conductive!) body is picking up. That will cause a little noise if the pickup is wound with ground-in (versus hot-in) and a LOT of noise if the pickup is wound hot-in.

Grounding the magnets solves both problems because it gives a path to ground for noise that the magnets are picking up - either passively, or when you touch them. Generally, magnets are either grounded or not when the pickup is built. Magnets are sensitive to heat, so you can't really solder to them. And they can't be drilled for a screw or other mechanical fastener without destroying them. So the typical path is to include a strip of copper foil tape along the bottom of the bobbin, touching each of the magnets. That copper can then be grounded, usually by either sticking a wire to it, or soldering a wire to it. That's what Nordstrand do - they put a strip of copper tape along the bottom of the bobbin and then solder a wire to it. That's also how that 96 art pickup is built. The copper tape acts to ground the slugs, and you get the benefit of a little additional shielding from the big flat piece of copper.

Some makers connect the copper foil to the ground side of the pickup coil, and other makers run a separate third lead from the pickup for the ground. I like the second approach, since it isolates the grounded components from the coil, and basically lets the pickup installer choose what to do with the ground. For instance, if you want, you can flip flop the leads from the coil and reverse the polarity of the pickup. You can't do that (easily) if the shielding is connected to one leg of the coil. Or, on a bass with a preamp that has an artificial ground, you can connect the shielding directly to "real" ground instead of pushing it through the preamp at the artificial ground. Audere preamps are an example where this is important to do.

Grounding the slugs is nice because then you don't have to worry about the coil wire orientation (hot-in or ground-in) and you get a quiet pickup either way, even if someone touches the slugs when they're not already grounded. It's kind of a win-win and it strikes me as odd when some pickup makers don't do it. If you have a pickup with slugs that are not grounded, and it's noisy, you can usually solve the problem by grounding/shielding the pickup yourself, by adding a strip of copper tape along the bottom, taping or soldering a wire to the copper, and grounding the wire.

It is possible for there to be downsides for having grounded slugs, but IME they're vastly less of a problem than the advantages. The big downside is that every time you touch a grounded slug, you will discharge whatever static electricity you have on your body through it. It's literally a one-time static discharge, and then the noise is pretty much zero. So, you get a pop. This almost never happens "in the wild" unless you bass has serious issues, since you discharge your static voltage any time you touch any grounded metal (i.e. THE STRINGS!) - so most people don't really ever build up much of a voltage while they're playing. You can try really hard to make this pop happen if you want to do so, but it's usually never a thing when you're playing.

As an aside note, just to be thorough, I don't know if the 96 art pickup you were testing had very good magnet slug grounding. The copper tape on the bottom was intact and grounded through the green lead on the pickup, so it was providing good shielding, but there may not have been good conductivity between the foil tape and the slugs. At one point in the video you were touching one of the slugs and it buzzed a bit, which tells me that slug didn't have good contact with the tape. That particular pickup was a bench test mule that had been rewound at least 8 or 9 times during testing, and repotted probably 4 or 5 times. So that tape has been heated and cooled over and over again, and the slugs have been dipped in hot wax over and over. It's easy for wax to wick in along the adhesive and slowly ruin the conductivity of the tape. I should have checked that before I sent it to you but I guess in the end since the pickup performed well in terms of noise, it's a positive "worst case" outcome.

And that raises a good point. If you're going to try grounding magnets yourself at home with copper tape, scrape the backs of the slugs before putting the tape on to make sure you're getting good contact with bare metal, and not bad contact through a layer of wax or epoxy or whatever the pickup was potted with.

 

[fig]

You take care of you. We can wait.

Personally, that sums it up for me, too. You don't owe us squat, man, and the bass stuff can wait. Do what ya gotta do. Just my opinion with my 4 cents (2 cents adjusted for inflation) included.

But if you really felt you owed us something, I think you could perform a free concert for us. Yeah...that's the ticket... And free beer for all, too. If your wife doesn't mind making massive quantities of Pigs in a Blanket, maybe some Jalapeno Poppers, too, that'd be great! I'm thinking Stairway to Heaven and Freebird should be on the setlist. Or combine the two for bonus points, Stairway to Freebird! Did I mention free beer for all?...

Ok, back to my housewife duties...

 

[bdplaid]

Pickup magnets are (typically) isolated from the coil winding by insulating tape wrapped over the slugs before the pickup is wound. Or, in some designs with a solid plastic bobbin, the slugs are pushed into holes through the core and there's plastic between the slug and the wire. At any rate, pretty much all pickups have the magnets insulated from the coil wire. if you check resistance from the coil to the magnets, you'll get an open circuit.

That leaves the magnets "floating" from a voltage perspective- they're not connected to anything and not part of the circuit. There is a danger associated with that in terms of noise, especially with designs where the magnets are exposed on the tops of the pickups, as is the case in traditional Fender designs. For one thing, the magnets are exposed to any noise that's radiating the pickups. They act like little antenna repeaters and radiate that noise right in the middle of the coil. In designs where there's only a thin layer of tape around the magnets (as in a Fender design where the bobbin is formed from flatwork pressed onto rods), the coil wire will be very closely coupled with the inner few hundred windings just because they're so physically close. Coils are wound such that the wire stacks up and builds thickness as it's wrapped on to the bobbin, so one en of the coil is naturally towards the middle of the pickup and the other end is naturally towards the outside. If the wire is wrapped such that the inner windings are on the "hot" end of the coil circuit, they will be very noisy.

The second noise risk of a pickup with floating magnets is contact with a human. If you are not grounded (i.e. not touching grounded metal on the bass) and you touch an exposed magnet, you turn the magnet into a tiny little antenna sending out a signal from all the noise your (very conductive!) body is picking up. That will cause a little noise if the pickup is wound with ground-in (versus hot-in) and a LOT of noise if the pickup is wound hot-in.

Grounding the magnets solves both problems because it gives a path to ground for noise that the magnets are picking up - either passively, or when you touch them. Generally, magnets are either grounded or not when the pickup is built. Magnets are sensitive to heat, so you can't really solder to them. And they can't be drilled for a screw or other mechanical fastener without destroying them. So the typical path is to include a strip of copper foil tape along the bottom of the bobbin, touching each of the magnets. That copper can then be grounded, usually by either sticking a wire to it, or soldering a wire to it. That's what Nordstrand do - they put a strip of copper tape along the bottom of the bobbin and then solder a wire to it. That's also how that 96 art pickup is built. The copper tape acts to ground the slugs, and you get the benefit of a little additional shielding from the big flat piece of copper.

Some makers connect the copper foil to the ground side of the pickup coil, and other makers run a separate third lead from the pickup for the ground. I like the second approach, since it isolates the grounded components from the coil, and basically lets the pickup installer choose what to do with the ground. For instance, if you want, you can flip flop the leads from the coil and reverse the polarity of the pickup. You can't do that (easily) if the shielding is connected to one leg of the coil. Or, on a bass with a preamp that has an artificial ground, you can connect the shielding directly to "real" ground instead of pushing it through the preamp at the artificial ground. Audere preamps are an example where this is important to do.

Grounding the slugs is nice because then you don't have to worry about the coil wire orientation (hot-in or ground-in) and you get a quiet pickup either way, even if someone touches the slugs when they're not already grounded. It's kind of a win-win and it strikes me as odd when some pickup makers don't do it. If you have a pickup with slugs that are not grounded, and it's noisy, you can usually solve the problem by grounding/shielding the pickup yourself, by adding a strip of copper tape along the bottom, taping or soldering a wire to the copper, and grounding the wire.

It is possible for there to be downsides for having grounded slugs, but IME they're vastly less of a problem than the advantages. The big downside is that every time you touch a grounded slug, you will discharge whatever static electricity you have on your body through it. It's literally a one-time static discharge, and then the noise is pretty much zero. So, you get a pop. This almost never happens "in the wild" unless you bass has serious issues, since you discharge your static voltage any time you touch any grounded metal (i.e. THE STRINGS!) - so most people don't really ever build up much of a voltage while they're playing. You can try really hard to make this pop happen if you want to do so, but it's usually never a thing when you're playing.

As an aside note, just to be thorough, I don't know if the 96 art pickup you were testing had very good magnet slug grounding. The copper tape on the bottom was intact and grounded through the green lead on the pickup, so it was providing good shielding, but there may not have been good conductivity between the foil tape and the slugs. At one point in the video you were touching one of the slugs and it buzzed a bit, which tells me that slug didn't have good contact with the tape. That particular pickup was a bench test mule that had been rewound at least 8 or 9 times during testing, and repotted probably 4 or 5 times. So that tape has been heated and cooled over and over again, and the slugs have been dipped in hot wax over and over. It's easy for wax to wick in along the adhesive and slowly ruin the conductivity of the tape. I should have checked that before I sent it to you but I guess in the end since the pickup performed well in terms of noise, it's a positive "worst case" outcome.

And that raises a good point. If you're going to try grounding magnets yourself at home with copper tape, scrape the backs of the slugs before putting the tape on to make sure you're getting good contact with bare metal, and not bad contact through a layer of wax or epoxy or whatever the pickup was potted with.

Awesome post!

 

[Crosscheck67]

Dig it. All your collective information continues to make me feel like I've struck literary gold. I do promise a demo of the completed project as a thank you. Just hang tight until I get there.

However, @fig a concert? I can't begin to articulate how disappointed you'd all be. I can promise great tone, but that's about it. My only shot would be to put a comedy slant on it, whatever that looks like.

That said, PM me if you're ever in Western MA. There will be beer. Oh yes, there will be beer.

 

[bdplaid]

I have to say, this has evolved into a rather good discussion of shielding, pickup noise, and design.