Magnets & Copper Wire: A Pickup Building Thread

[Will_White]

I'm struggling with this a bit. My humbucker picks up the signal, but it hums. What am I doing wrong?

I have an alnico 5 bar magnet with 2 rail pole pieces. I have my preamp, which is silent with no coils connected. I've tried two clockwise coils and I've tried one clockwise and one anticlockwise. I've also tried each coil as a single coil. Each single coil works as a pickup but hums. more so if you touch the rail or if you grip the coil between thumb and finger. Any two coils wired in series works the same but is louder (as you'd expect). Reverse either coil and the signal cancels out. All good but it still hums. One final test, I wired one pickup to the inverting input of the amplifier and one to the non inverting input. It does buck hum in that configuration, but is as quiet as a single coil.

Surely having two coils in series, one north up one south up should buck hum. Why might mine not be?

You need the coil polarity to be reversed and the magnetic polarity to be reversed. The magnets don't effect hum it's just the coils, reversing the magnets brings the signal back in phase.

 

[smart51]

This is interesting. If I ground one of the rails AND touch it, the noise goes away. Grounding it alone has no effect, so it's not a solution to the problem.

The noise is a hum typical of an amp with a grounding problem. It is like 50Hz hum but more nasal, there's probably some 100Hz in there as well. It's odd that it goes away in differential amp configuration.

 

[slowburnaz]

This is interesting. If I ground one of the rails AND touch it, the noise goes away. Grounding it alone has no effect, so it's not a solution to the problem.

The noise is a hum typical of an amp with a grounding problem. It is like 50Hz hum but more nasal, there's probably some 100Hz in there as well. It's odd that it goes away in differential amp configuration.

In any case, grounding both blades is a good idea. Could you have a grounding issue elsewhere?

And this probably doesn’t have any bearing on your issue, but I also always make my coil starts the “cold” leads that go to ground.

 

[Freekmagnet]

This is interesting. If I ground one of the rails AND touch it, the noise goes away. Grounding it alone has no effect, so it's not a solution to the problem.

The noise is a hum typical of an amp with a grounding problem. It is like 50Hz hum but more nasal, there's probably some 100Hz in there as well. It's odd that it goes away in differential amp configuration.

Is this pickup installed in a bass with strings?

 

[yberwaffe]

And this probably doesn’t have any bearing on your issue, but I also always make my coil starts the “cold” leads that go to ground.

What do you mean by cold lead ?

If you ground the coil wire that comes from the outermost layer, wouldn't that make the outermost layer act like a shield ?
Have anyone tried this and see if it makes a difference ?

 

[Max Bogosity]

This is interesting. If I ground one of the rails AND touch it, the noise goes away.

When I've had that problem it was because the ground and live were reversed.

 

[smart51]

Is this pickup installed in a bass with strings?

No, it's on a bench. I'm bringing a bass close to it to test the output

 

[Freekmagnet]

No, it's on a bench. I'm bringing a bass close to it to test the output

Ah, I thought so. Just ground both blades and put the pickup in your bass. As long as the pickup is a part of the circuit, the buzz will go away when you put your hands on the strings. The circuit has to actually be grounded to something, and in the case of electric guitars and basses, you are the ground.

 

[SamanthaCay]

Is a post about a pickup test bed relevant enough to throw in here?

Put this together this weekend from some unloved parts I had lying around. It's got a couple issues to work out but otherwise is pretty much done and gonna be super useful.

Still on this topic I've been thinking about a test rig for applying a signal source to a pickup at a similar to a string amplitude. Haven't quite figured a way to do that yet though. Anybody got anything on that front? The ideal for me would be to be able to throw a signal gen at it and scope test just like I would any other audio device but the mechanical aspect complicates things.

Would be sweet to be able to graph the frequency response of a pickup along with it's impedance.

 

[SamanthaCay]

@smart51 I went through something similar recently with a mudbucker which I rewound on one side.

I tried on the bench and in frustration ended up with it in the bass it was destined for. However it was a pain to remove and reinstall a couple times due to the magnets not being right, I don't think I could have done it had it just been on the bench. (This was a huge motivation to get my test bed made) anyway clip leads helped a ton here as well and this was also good as it allowed me to get in phase with my other pickup.

 

[Freekmagnet]

Is a post about a pickup test bed relevant enough to throw in here?
View attachment 4825514 View attachment 4825515
Put this together this weekend from some unloved parts I had lying around. It's got a couple issues to work out but otherwise is pretty much done and gonna be super useful.

Still on this topic I've been thinking about a test rig for applying a signal source to a pickup at a similar to a string amplitude. Haven't quite figured a way to do that yet though. Anybody got anything on that front? The ideal for me would be to be able to throw a signal gen at it and scope test just like I would any other audio device but the mechanical aspect complicates things.

Would be sweet to be able to graph the frequency response of a pickup along with it's impedance.

Dang, that’s a pretty swanky test bed! Haha I usually just twist the ends of my wires together!

I’m digging’ that floral print pickup cover. Nice!

 

[Jon Clegg]

@smart51
Still on this topic I've been thinking about a test rig for applying a signal source to a pickup at a similar to a string amplitude. Haven't quite figured a way to do that yet though. Anybody got anything on that front? The ideal for me would be to be able to throw a signal gen at it and scope test just like I would any other audio device but the mechanical aspect complicates things.

Would be sweet to be able to graph the frequency response of a pickup along with it's impedance.

I've used Audacity to generate a frequency swept sine-wave, pumped it out through the headphone jack into 2 of these (modified by removing the buzzer, leaving the inductor) wired in parallel. I then recorded the output back into Audacity and used a spectrum analysis tool to plot the response. While it isn't calibrated, I did allow me to see how various tone control configurations affected the response relative to the baseline.

 

[SamanthaCay]

I've used Audacity to generate a frequency swept sine-wave, pumped it out through the headphone jack into 2 of these (modified by removing the buzzer, leaving the inductor) wired in parallel. I then recorded the output back into Audacity and used a spectrum analysis tool to plot the response. While it isn't calibrated, I did allow me to see how various tone control configurations affected the response relative to the baseline.

I didn't know those had inductors in them! Thought they were just piezos. Anyway I think this is probably the way forward, maybe I should roll my own inductor?? I do QC for WMD so I have access to a nice rigol scope and my test case has a couple oscillators, so I'm good in that department.

 

[Jon Clegg]

I discovered these by accident watching a YT video about making a sustainer.

 

[NKBassman]

Is a post about a pickup test bed relevant enough to throw in here?
View attachment 4825514 View attachment 4825515
Put this together this weekend from some unloved parts I had lying around. It's got a couple issues to work out but otherwise is pretty much done and gonna be super useful.

Still on this topic I've been thinking about a test rig for applying a signal source to a pickup at a similar to a string amplitude. Haven't quite figured a way to do that yet though. Anybody got anything on that front? The ideal for me would be to be able to throw a signal gen at it and scope test just like I would any other audio device but the mechanical aspect complicates things.

Would be sweet to be able to graph the frequency response of a pickup along with it's impedance.

Love the termination strip!

 

[slowburnaz]

Is a post about a pickup test bed relevant enough to throw in here?
View attachment 4825514 View attachment 4825515
Put this together this weekend from some unloved parts I had lying around. It's got a couple issues to work out but otherwise is pretty much done and gonna be super useful.

Still on this topic I've been thinking about a test rig for applying a signal source to a pickup at a similar to a string amplitude. Haven't quite figured a way to do that yet though. Anybody got anything on that front? The ideal for me would be to be able to throw a signal gen at it and scope test just like I would any other audio device but the mechanical aspect complicates things.

Would be sweet to be able to graph the frequency response of a pickup along with it's impedance.

That's a seriously cool test bed bass you've got there. Reminds me of a much cleaner version of one of the old test bed "basses" that Leo Fender used back in the day: https://www.guitarworld.com/news/be...used-as-a-quick-and-dirty-way-to-test-pickups

 

[smart51]

What is a good way to ground the pickup rails and magnet? I can't weld copper wire to a steel rail or alinco magnet. Glue tends not to be conductive. If I'm happy I'll epoxy pot the coils into a soapbar case. The epoxy is likely to spoil any contact between copper wire and steel rail. Any ideas?

 

[SamanthaCay]

What is a good way to ground the pickup rails and magnet? I can't weld copper wire to a steel rail or alinco magnet. Glue tends not to be conductive. If I'm happy I'll epoxy pot the coils into a soapbar case. The epoxy is likely to spoil any contact between copper wire and steel rail. Any ideas?

Conductive adhesive copper tape would work.

 

[Honkey tonk]

Is a post about a pickup test bed relevant enough to throw in here?
View attachment 4825514 View attachment 4825515
Put this together this weekend from some unloved parts I had lying around. It's got a couple issues to work out but otherwise is pretty much done and gonna be super useful.

Still on this topic I've been thinking about a test rig for applying a signal source to a pickup at a similar to a string amplitude. Haven't quite figured a way to do that yet though. Anybody got anything on that front? The ideal for me would be to be able to throw a signal gen at it and scope test just like I would any other audio device but the mechanical aspect complicates things.

Would be sweet to be able to graph the frequency response of a pickup along with it's impedance.

Nice work!

 

[RichterScale]

What is a good way to ground the pickup rails and magnet?

Drill and tap for a small machine screw and crimp a small ring terminal on the end of the ground wire, is one option.