Pickup coils from multi-layer PC boards

[Hugh Evans]

I know I've seen at least one patent application pertaining to this concept US20120272815 A1, and given my current interest in all things low-z, I'm curious if anyone here has played with this concept or has any thoughts on the topic.

For the past several months I have been experimenting primarily with traditional pickup geometries and coils using heavy gauge magnet wire, and the results have been fantastic. There has been no shortage of fun, and I can confirm that nothing else sounds quite like a 10 ohm humbucker. My proprietary active electronics are what set my designs apart from what has been done before, but that's another story. The thread regarding current sensing transformers and alumitones is for some reason what brought me to this particular concept. Theoretically, a heavily plated PC board can be made to have favorable electrical characteristics for use with a current sensing transformer using a single layer... Which is a neat idea I intend to experiment with at some point. However, I'm a believer in maintaining relatively traditional coil geometry in the interest of obtaining similar harmonic content to typical pickups. Thanks to the etching process instead of winding, unorthodox and otherwise impossible winding patterns are on the menu. Instead of scatter-winding, it should be possible to create optimized patterns for virtually any desired characteristics *and* attain perfect repeatability. I envision ordering them in bulk from PC board fabricators in multi-layer form, and depending on how pronounced the effect of crazy patterns turns out to be, making it possible to customize their character based on how modular blocks are stacked. Additionally, the surface mount active electronics can simply be placed on the bottom layer. From a standpoint of production and quality control it has more than a little bit going for it.

I'm still having a blast designing a CNC coil winder for traditional fabrication of pickups and transformers... But alternative concepts are too much fun to ignore. With all that said, I am very curious to hear about any first hand experience any of you have had with this approach. Otherwise, this should make an excellent starting point for a thought experiment. There are more than enough warped minds around here to enjoy thoroughly pondering the possibilities. If there is sufficient interest in doing a short prototype production run I propose pooling our cash so we can all save some money while tinkering.

I look forward to all of your input. This should be fun.

[bbsailor]

I know I've seen at least one patent application pertaining to this concept US20120272815 A1, and given my current interest in all things low-z, I'm curious if anyone here has played with this concept or has any thoughts on the topic.

For the past several months I have been experimenting primarily with traditional pickup geometries and coils using heavy gauge magnet wire, and the results have been fantastic. There has been no shortage of fun, and I can confirm that nothing else sounds quite like a 10 ohm humbucker. My proprietary active electronics are what set my designs apart from what has been done before, but that's another story. The thread regarding current sensing transformers and alumitones is for some reason what brought me to this particular concept. Theoretically, a heavily plated PC board can be made to have favorable electrical characteristics for use with a current sensing transformer using a single layer... Which is a neat idea I intend to experiment with at some point. However, I'm a believer in maintaining relatively traditional coil geometry in the interest of obtaining similar harmonic content to typical pickups. Thanks to the etching process instead of winding, unorthodox and otherwise impossible winding patterns are on the menu. Instead of scatter-winding, it should be possible to create optimized patterns for virtually any desired characteristics *and* attain perfect repeatability. I envision ordering them in bulk from PC board fabricators in multi-layer form, and depending on how pronounced the effect of crazy patterns turns out to be, making it possible to customize their character based on how modular blocks are stacked. Additionally, the surface mount active electronics can simply be placed on the bottom layer. From a standpoint of production and quality control it has more than a little bit going for it.

I'm still having a blast designing a CNC coil winder for traditional fabrication of pickups and transformers... But alternative concepts are too much fun to ignore. With all that said, I am very curious to hear about any first hand experience any of you have had with this approach. Otherwise, this should make an excellent starting point for a thought experiment. There are more than enough warped minds around here to enjoy thoroughly pondering the possibilities. If there is sufficient interest in doing a short prototype production run I propose pooling our cash so we can all save some money while tinkering.

I look forward to all of your input. This should be fun.

Hugh,

It is good to see others experimenting with low-Z and current-based pickups.

Keep one thing in mind.. the total resistance of the primary string loop, or in your case the PC board etching coil resistance, will dictate the output impedance espicially single turn current transformer primaries. If you are using multiple turn low impedance input transformers in the .5 to about the 2 ohm DCR range, you have a little more lattitude in the PC board etching resistance and can control the output impedance, bandwidth and pickup voicing. Post your experimental results so we can all extend our knowledge of your PC board etching techniques and the sounds they produce.

Joseph Rogowski

[David Schwab]

I thought about trying this like 30 years ago, but never did. I got the idea from looking at microwave guides back when I worked at ITT. My brother used to have to photograph the art work for these printed coils on a stack camera, and it had to be accurate or it wouldn't work right. I thought it would be a col way to make a low Z coil for a pickup.

[Joe Gwinn]

Also look at patent application 20120103169.

Anaren is a maker of microwave components (which sells to defense and wireless industries), all three inventors work there, and the lead inventor (Thomas Lingel) on these magnetic pickup patents also invented a microwave circulator, and is the Director of Engineering for the microwave dielectrics part of Anaren.

Graeme Bunce is a engineering manager in the microwave dielectrics at Anaren.

And Mark Bowyer is business development manager at Anaren.

I can understand engineers moonlighting as musicians et al. But the patent will be assigned to Anaren. Usually companies are not interested in employee's patents in unrelated areas.

There has to be a good story here - a microwave component company starts making guitar pickups? True diversification?

[David King]

Well Bill Bartolini got his start at Lawrence Livermore Labs.
Done Lace Sr started Actodyne General coming from a background in lighting, relays, solenoids etc.
Lace Music Products | Since 1979 - Lace Sensor electric guitar pickups, Alumitone, bass pickups, California Acoustic pickups - A pickup for any style of music.

[David Schwab]

I can understand engineers moonlighting as musicians et al. But the patent will be assigned to Anaren. Usually companies are not interested in employee's patents in unrelated areas.

When I first started at ITT I had to sign a paper stating that anything I invented and patented while working there, even on my own, would be assigned to them. I had to list all my previous inventions so that they would be exempt.

Maybe they are doing something similar. I had a few things I wanted to get patented at the time, and held off doing so. Then I just never got around to it.

But you can see that kind of thing used in microwave technology.

[Hugh Evans]

Yeah, corporate invention clauses vary all over the map. I actually have a rather odd arrangement with my last employer that amounts to shared IP rights, so I can still take all of my conceptual work to a competitor.

It certainly sounds like there's more to the story on these particular applications.

At the very least I think this will be a fun project to dabble with.

[ScottA]

When I first started at ITT I had to sign a paper stating that anything I invented and patented while working there, even on my own, would be assigned to them. I had to list all my previous inventions so that they would be exempt.

Maybe they are doing something similar. I had a few things I wanted to get patented at the time, and held off doing so. Then I just never got around to it.

But you can see that kind of thing used in microwave technology.

They really can't enforce that. They can only bind you to things that relate to your job or that you use their resources to develop. If you do something on your own time and dime that does not relate to your job function, they have no legal right to the IP.

[Hugh Evans]

As long as the invention is unrelated to your employment and did not require or make use of the company's resources, you're absolutely right. However, in the cases being discussed in this thread the grounds for the invention appear to directly result from projects completed in the course of working... So even though the idea of using an invention in a completely unrelated/unintended manner might sound like grounds for retaining it as your own IP, the employer can still elect to retain it for themselves. It's also not necessarily a bad thing to have patents held by your employer, since patents only afford the right to protect your invention with the help of lawyers. I have the rights to several pieces of IP in the adhesives industry and have no plans to patent them myself, because it would be pointless without sufficient financial/legal backing to deter infringement.

IP law is weird. In the case of the referenced patents in this thread, for all we know the inventors worked out a favorable deal with the company.

[David Schwab]

They really can't enforce that. They can only bind you to things that relate to your job or that you use their resources to develop. If you do something on your own time and dime that does not relate to your job function, they have no legal right to the IP.

Until you sign the document. But I thought it was kind of absurd.

[ScottA]

Until you sign the document. But I thought it was kind of absurd.

Well, signing it does complicate things, but it generally wouldn't hold up in court.

Some states might be more problematic than others. I know it wouldn't wash in DE. Trust me, I researched it... ;-). I even had a copy of the relevant documentation at the ready when I was having my exit debriefing conversations.

[David Schwab]

Well, signing it does complicate things, but it generally wouldn't hold up in court.

Some states might be more problematic than others. I know it wouldn't wash in DE. Trust me, I researched it... ;-). I even had a copy of the relevant documentation at the ready when I was having my exit debriefing conversations.

It was a long time ago, so I'm not worried about it.

[Steve Conner]

These printed coils are quite popular in switching power supplies. The transformer windings are formed right inside a multi-layer PCB, with a couple of holes routed in it for a ferrite core. The jargon term is "planar transformers".

[Hugh Evans]

I came across the planar transformer core not long ago, and it has made researching design parameters much easier. Ultimately, there's plenty of new ground to tread as they apply to guitar pickups. New concepts are popping up along the way, such as integrating a matching transformer before going into the preamp. Assuming everything works as I hope, this could prove to be a wonderfully flexible platform for anyone who doesn't mind deviating from traditional designs. Cost of fabrication will also likely be far below that of wound pickups. From the standpoint of IP, using PC boards opens another option: copyrighting trace patterns. Companies such as Mesa Boogie have done exactly that with their amps for years. It's not a strategy I plan to employ, but it's nice to have ideas in your back pocket.

Anyways, the weather should be warming up soon (when you start a company in a garage, lack of climate control can be a very annoying reality) at which point I can grab a bunch of PC boards and run them through my CNC router to quickly throw together a proof of concept.

[Mike Sulzer]

Cost of fabrication will also likely be far below that of wound pickups.

You need lots of turns either on the pickup or on the secondary of the matching transformer, so either wind a pickup, or wind/buy a transformer. I am not sure it makes much difference.