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Topic: Dummy Coils ? |
basilh
From:
United Kingdom
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Posted 28 Jun 2008 5:13 am |
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I got this very interesting e-mail
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Howdy!
Recently I have had a few requests for “Dummy Coils” and it seemed natural to write a note on this topic.
What are dummy coils and what are they used for?
Dummy coils are similar to single coil magnetic pickups, but have no magnets and therefore cannot generate sound from the vibrating strings as guitar pickups do. Dummy coils are used to eliminate a significant amount of the 60 cycle AC noise that single coil pickups are susceptible to. Because dummy coils do not generate a signal from the vibrating strings they are often used to eliminate noise with minimal affect on the single coil tone of the guitar pickup.
My colleague, Christopher Tatoyian recently installed a dummy coil made by Vintage Vibe Guitars in his Gibson Melody Maker and recorded sound clips with and without the dummy coil active in the circuit. To hear the noise cancellation which can be achieved with a dummy coil please listen to the two dummy coil sound clips posted at the top of the following webpage:
http://www.vintagevibeguitars.com/sound.html
Tech stuff:
Noise signals from external sources (AC transformers, 120 VAC dimmer switches, florescent lights, etc.) can be intercepted by guitar pickups and enter the signal which ultimately is delivered to an amplifier. There are generally four ways one can eliminate this noise:
Eliminate the noise at the source
Shield the pickups and guitar controls circuit from the noise
“cancel” the noise as is done in a humbucking pickup
Use a noise gate between the guitar and the amplifier
In this article I will focus on option c: noise cancellation. Before we discuss interaction of signals it is best to review how a single coil magnetic pickup works. The electrical signal generated by a single coil passive magnetic pickup in an electric guitar, bass guitar or other similar stringed instrument is an alternating current (AC) waveform. If you could see this AC signal it would look like a repeating wave with peaks and valleys. This AC signal is generated in a pickup when the guitar strings vibrate within the magnetic field of the permanent magnets in a pickup. Magnetic material (iron and nickel) in the vibrating guitar strings cause the magnetic field of the permanent magnets in the pickup to fluctuate at the same frequency as the vibrating strings. This fluctuating magnetic field causes electrons in the copper coil windings of the pickup to oscillate which generates the AC electrical signal in the pickup. AC noise signals from things such as electrical dimmer switches and florescent lights are broadcast just like radio waves and these signals can be intercepted by the pickups or the controls circuit in a guitar. Humbucking pickups utilize two coils to simultaneously boost the strength of the signal from the vibrating strings and reduce or eliminate noise from external AC sources. Usually the two coils of a humbucking pickup are electrically connected to each other in series and the coils are made such that one coil is wound clockwise and the other coil is wound counter clockwise. In addition to this, the magnetic field orientations of the two coils are opposite from each other (one coil has a magnetic field oriented north up, the other coil is south up). The signal from the vibrating strings in one coil adds constructively to the signal generated in the other coil from the strings because these two signals are in phase. The reverse winding direction of the two coils shifts the AC waveform 180 degrees and the opposite magnetic field direction of the two coils reverses the phase orientation another 180 degrees putting the signals generated by the vibrating strings above the two coils back into phase. The noise signal entering the two coils of a humbucker is unaffected by the magnetic fields of the two coils; the noise signal in one coil is out of phase with the noise signal in the other coil and cancels. A dummy coil can offer similar noise cancellation as described for a humbucking pickup but will not boost the signal from the vibrating strings.
Installing a dummy coil:
For best noise canceling results a dummy coil should be as similar as possible to the guitar pickup it is paired with and exposed to the same noise environment as the guitar pickup. The dummy coil should have a similar coil design (number of turns on the coil, coil wire gauge and coil geometry) as the guitar pickup. To make the noise environment of the pickup and dummy coil as similar as possible the dummy coil and pickup should both be located in the instrument as close as feasible to each other and in the same orientation. If the guitar pickup has grounded shielding, the dummy coil should have grounded shielding also. As a practical note a dummy coil should be securely fastened in the instrument controls cavity to prevent it from moving around and becoming damaged or causing electrical shorts in the controls circuit. The dummy coil can be wired to the pickup either in series or in parallel. In either case the dummy coil should be wired such that the winding direction of the dummy coil is opposite of the winding direction of the pickup to cancel the noise signal.
Dummy coils are available from Vintage Vibe Guitars in a variety of designs to match specific pickups; please contact us for more information regarding dummy coils.
My congratulations to all of you who have read all the way through this newsletter!
I hope this information is helpful to you.
Best Wishes.
If you do not wish to receive Tech Tips, please reply with "Unsubscribe". Thank you.
Pete Biltoft
Vintage Vibe Guitars
website: www.vintagevibeguitars.com
email: vintagevibeguitars@gorge.net |
Well ? what's the skinny ?
_________________
Steelies do it without fretting
CLICK THIS to view my tone bars and buy——> |
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Don Sulesky
From:
Citrus County, FL, Orig. from MA & NH
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Posted 28 Jun 2008 5:35 am
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| Why not just replace the pickup with a humbucker pickup? |
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basilh
From:
United Kingdom
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Posted 28 Jun 2008 11:58 am
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| Don Sulesky wrote: |
| Why not just replace the pickup with a humbucker pickup? |
Tonality difference.. |
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Donny Hinson
From:
Glen Burnie, Md. U.S.A.
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Posted 28 Jun 2008 4:25 pm
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But, the dummy coil also changes the tone? (Though slightly.)
I'd just get a humbucker with the tone I wanted, and be done with it (though the D/C might be a better choice for installation into vintage, collector-type instruments). |
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Twayn Williams
From:
Portland, OR
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Posted 29 Jun 2008 11:08 am
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You're either a humbucker person or a single-coil person and ne'er the twain shall meet.
_________________
Primitive Utility Steel |
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Joseph Meditz
From:
Sierra Vista, AZ
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Posted 29 Jun 2008 5:38 pm
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It is interesting that the signal sounds louder with the dummy coil installed. The time plots on the right hand side are with the dummy coil installed.
Joe
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John Billings
From:
Ohio, USA
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Posted 29 Jun 2008 6:03 pm
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There's just something about humbucker's high end. They lack the complex character of single coils. The harmonic complexity is gone, I have more than 20 6-strings and 6 pedal steels, The only guitar that has humbuckers is my Zion with 3 Bardens,
Humbuckers were invented to eliminate hum. Unfortunately, they eliminated much more than hum. |
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Twayn Williams
From:
Portland, OR
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Posted 29 Jun 2008 9:11 pm
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| John Billings wrote: |
There's just something about humbucker's high end. They lack the complex character of single coils. The harmonic complexity is gone, I have more than 20 6-strings and 6 pedal steels, The only guitar that has humbuckers is my Zion with 3 Bardens,
Humbuckers were invented to eliminate hum. Unfortunately, they eliminated much more than hum. |
Amen brother!
Although I hear lots of humbucker guitars I like, it just only when other people are playing 'em!
Dummy coils that are installed in the guitar are an old technique that works, but not as well as the new generation of noiseless offerings from Dimarzio, Kinman and from what I hear, the backplate system from Suhr. I've tried about every strat noiseless pup out there and they all lack sparkle. But the new ones are really close and worth having in at least one guitar for those situations where a single coil is just too noisy.
I'd like it if Bill Lawrence would work his noiseless mojo on some steel guitar models! However, that being said, I am 100% happy with my 12k True Tone!
_________________
Primitive Utility Steel |
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Jay Ganz
From:
Out Behind The Barn
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Posted 30 Jun 2008 4:50 am
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I got ahold of this Tele with 3 Kinman pickups in it.
I have to admit, they sound pretty amazing. True single coil tone with no hum.
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James Collett
From:
San Dimas, CA
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Posted 30 Jun 2008 6:51 pm
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Yeah, but what about stacked humbuckers?
Wouldn't those act more like "dummy coils" than humbuckers, as one coil is receiving a large majority of the signal?
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James Collett |
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Twayn Williams
From:
Portland, OR
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Posted 1 Jul 2008 12:07 pm
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| James Collett wrote: |
Yeah, but what about stacked humbuckers?
Wouldn't those act more like "dummy coils" than humbuckers, as one coil is receiving a large majority of the signal? |
Not if you have magnets going through both coils. When you have the magnets only going through the top coil, then that's close to what the new breed of noiseless pups do. Otherwise you have a stacked humbucker which sounds a whole lot like a side by side humbucker of the same size.
_________________
Primitive Utility Steel |
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Bill Creller
From:
Saginaw, Michigan, USA (deceased)
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Posted 4 Jul 2008 7:34 am
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I guess I don't get out enough. I hadn't heard of dummy coils, but it makes sense alright. I do use humbuckers though, 7 string DiMarzios for some lap steels. Everything else I have is horseshoe single coil types with Lollar windings.
I have a couple humbuckers from Ebay, maybe I'll try pushing the poles out of one side to check the difference. (they were cheap  ) |
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