Magnets & Copper Wire: A Pickup Building Thread

[Honkey tonk]

Rc connectors are slick for hot swapping

https://www.amazon.com/Connector-Co...sInFzcCI6IjUuMDAifQ==&sprefix=,aps,123&sr=8-5

 

[Honkey tonk]

View attachment 4825881

 

[Honkey tonk]

strings stay on for a sorta quick swap , been working on a double coil for this . mabey someday I will finish it

 

[yberwaffe]

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.

Wouldn't a coil from a guitar pickup be better, it runs along the whole pickup if put on top of the pickup you are measuring.
A signal generator usually have pretty low output impedance (50 ohm or so) so I doubt you need a power amp to drive the coil.

 

[yberwaffe]

About the test bed bass.
How much wood can be removed without the body giving in and bend ?

 

[smart51]

Success at last. The first couple of coils I wound were a bit loose and very microphonic, so I've wound two more with more tension and using the new wire. It works. Copper tape on the magnet and rails connected to earth. It is quiet unless you squeeze the coils between finger and thumb, which you're not going to do when it is under its cover. I've wax potted it and it still works. Now I've got to fit it to a bass and try it.

 

[Jon Clegg]

Rc connectors are slick for hot swapping

https://www.amazon.com/Connector-Compatible-Spektrum-Receiver-Connection/dp/B09TSF6W8B/ref=sr_1_5?crid=386R44OXZT2G7&keywords=rc+connectors&qid=1664223190&qu=eyJxc2MiOiI1LjQ3IiwicXNhIjoiNS4xNiIsInFzcCI6IjUuMDAifQ==&sprefix=,aps,123&sr=8-5

Yeah I've been using these for internal connections, they're also known as Dupont connectors. Getting the crimpers makes life a lot easier.

 

[SamanthaCay]

Wouldn't a coil from a guitar pickup be better, it runs along the whole pickup if put on top of the pickup you are measuring.
A signal generator usually have pretty low output impedance (50 ohm or so) so I doubt you need a power amp to drive the coil.

What we were talking about is something based on a Fernandez sustainer which uses a low resistance coil (~8 ohm @1khz Z). This gets pushed by a small amp to create induction between the two coils.

I could be wrong but I'd assume the reason you wouldn't want to run a large resistance coil at a lower amplitude is because with the losses involved you'd end up with very little inducted signal at your secondary. (Reasons a humbucker doesn't create a feedback loop)

 

[SamanthaCay]

About the test bed bass.
How much wood can be removed without the body giving in and bend ?

A lot apparently. Twas a concern and I'll keep an eye on it but I don't think this body is going to taco anytime soon. The back is just a .25" of pine I had and the thin layer of sheet metal. It gets it's structure from the lower half of the body and being well joined in place via a .25" channel routed around the perimeter of the pool. I suppose if it did want to bend there's always the option of inlaying a strip of steel up the backside, but it doesn't seem like that'll be needed here.

 

[slowburnaz]

This might be an odd place to do this, but seeing as how we seem to have a few folks in here that are good with electronics…. I was wondering if anyone here could help with my wiring diagram question: Wiring / Switching Diagram Request

I’m able to grok a DPDT switch well enough, but getting a 3P3T on-on-on to do what I describe in that thread has me thrown for a loop.

 

[Kinkh]

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.

This might be a bit tricky if you want to go full scientific on how to measure this. What has been said in this thread already, you would need some kind of coil to produce a magnetic field filed which would excite the pickup being tested.
For the measurement to be accurate, the generator coil must not interfere with the measurement. That being said it would need to produce a magnetic filed with a constant amplitude at all (relevant) frequencies. For a coil to be able to do that, it would need to be connected to a constant current source that produces a sweep signal. Which means that connecting directly to the output of a normal signal source will make the measurement inaccurate (since it's not a constant current source).

Technically a circuit between the signal generator and test coil is needed. I've done some tests at uni about 10 years ago (simple amplifier with a resistor in series to make a "current source"), and the results were meh - not good, not terrible. Sometime later I played around with some simulations, and it would seem that playing around with the placement of the test coil inside a high current opamp might make the current constant at all frequencies. But I forgot the details and never managed to test the circuit in reality

One other important thing to note here - in this kind of measurement you only measure the characteristic of the pickup coil, not the magnets. So while it is definitely useful to for measuring the frequency response of the pickup coil, it doesn't take into account the influence of the magnet (pole pieces, their position, other metal parts, etc.)

Anyways, I hope this info might be helpful.

 

[SamanthaCay]

This might be a bit tricky if you want to go full scientific on how to measure this. What has been said in this thread already, you would need some kind of coil to produce a magnetic field filed which would excite the pickup being tested.
For the measurement to be accurate, the generator coil must not interfere with the measurement. That being said it would need to produce a magnetic filed with a constant amplitude at all (relevant) frequencies. For a coil to be able to do that, it would need to be connected to a constant current source that produces a sweep signal. Which means that connecting directly to the output of a normal signal source will make the measurement inaccurate (since it's not a constant current source).

Technically a circuit between the signal generator and test coil is needed. I've done some tests at uni about 10 years ago (simple amplifier with a resistor in series to make a "current source"), and the results were meh - not good, not terrible. Sometime later I played around with some simulations, and it would seem that playing around with the placement of the test coil inside a high current opamp might make the current constant at all frequencies. But I forgot the details and never managed to test the circuit in reality

One other important thing to note here - in this kind of measurement you only measure the characteristic of the pickup coil, not the magnets. So while it is definitely useful to for measuring the frequency response of the pickup coil, it doesn't take into account the influence of the magnet (pole pieces, their position, other metal parts, etc.)

Anyways, I hope this info might be helpful.

Damn good stuff here. I had a feeling this would be more complex than it seems on the surface. I'd assume if it weren't someone (pickup manufacturers) would have already done it.

 

[NKBassman]

Could you use a small speaker motor for this? When you hold your phone speaker close to a pickup, the output of the speaker makes its way to the amp.

 

[Kinkh]

Damn good stuff here. I had a feeling this would be more complex than it seems on the surface. I'd assume if it weren't someone (pickup manufacturers) would have already done it.

It can be complex depending on the level of detail and accuracy of measurements one wants to do.
I'm assuming pickup manufacturers were never that much interested in raw technical measurements as in how something subjectively sounds. Or maybe they were but nobody published stuff relating to that.

If you or anyone lese might be interested, I could try to do that simulation again when I'm free (in some two weeks or so), and give you a schematic which you can test.

Could you use a small speaker motor for this? When you hold your phone speaker close to a pickup, the output of the speaker makes its way to the amp.

Any coil that can produce a magnetic filed perpendicular into the pickup can work. It's just the accuracy that not be good. As with any measurement - the tool used to measure something must not interfere with the thing being measured

 

[ardgedee]

I'm assuming pickup manufacturers were never that much interested in raw technical measurements as in how something subjectively sounds. Or maybe they were but nobody published stuff relating to that.

My suspicion is that most of the popular manufacturers are extremely interested in the technical specifications of their products (at the very least, it helps with quality control in production), and also that they also consider those specs to be proprietary information that they will never ever make public.

 

[Honkey tonk]

Kinda odd considering microphones have/ give all the specs upfront, maybe it's a demographic thing ?

Look at the knobs on a typical amp, doesn't really tell you what's going on when you turn them
On a console, knobs pretty much tell you everything

You can buy a 30 dollar mic that tells frequency response and polar patern

 

[yberwaffe]

Maybe the pickup manufactures DON'T WANT to show the measurements because it makes it much harder to sell them on hype alone.
This is an interesting topic indeed.

 

[Kinkh]

I think we all might be onto something here... They don't want to give out all the details for sure; they want to keep the hype, they don't want to publish their "secrets", they might people wouldn't be interested etc...

I for one can't stand not knowing what each knob does on an amp or pedal - I'm the happiest person on Earth if I can get my hands on a schematic and give it a deeper look
Just wish details on more things were readily available...

 

[Honkey tonk]

Imagine if Jason lamb made consoles

 

[KidAmnesia]

This might be a bit tricky if you want to go full scientific on how to measure this. What has been said in this thread already, you would need some kind of coil to produce a magnetic field filed which would excite the pickup being tested.
For the measurement to be accurate, the generator coil must not interfere with the measurement. That being said it would need to produce a magnetic filed with a constant amplitude at all (relevant) frequencies. For a coil to be able to do that, it would need to be connected to a constant current source that produces a sweep signal. Which means that connecting directly to the output of a normal signal source will make the measurement inaccurate (since it's not a constant current source).

Technically a circuit between the signal generator and test coil is needed. I've done some tests at uni about 10 years ago (simple amplifier with a resistor in series to make a "current source"), and the results were meh - not good, not terrible. Sometime later I played around with some simulations, and it would seem that playing around with the placement of the test coil inside a high current opamp might make the current constant at all frequencies. But I forgot the details and never managed to test the circuit in reality

One other important thing to note here - in this kind of measurement you only measure the characteristic of the pickup coil, not the magnets. So while it is definitely useful to for measuring the frequency response of the pickup coil, it doesn't take into account the influence of the magnet (pole pieces, their position, other metal parts, etc.)

Anyways, I hope this info might be helpful.

I get that to take scientific accurate measurements you'd need a calibrated system; but with any inductor you can take comparative measures which would be the most useful side of this. As long as you keep the inductor and input signal the same, you can use it to compare a coil you wound to the coil in a pickup that you know well and from there infere how your coil will work.