ampage Tube Amps / Music Electronics	For current discussions, please visit Music Electronics Forum.

ampage archive

Vintage threads from the first ten years

What effects inductance

9/4/2002 7:45 AM
Tony@Mastertone	What effects inductance As you may have noticed... I have been asking a few simple questions and asking for everyones input so the not so experienced guys can soak up the info, as sometimes when your new to something you just dont know what questions to ask.... So.... in everyones opinion, (please, without going into rocket science)... 1. What effects inductance???? and 2. How does this relate to output and tone??? i.e. Is it a mechanical relationship, electrical.. or a combination of both etc.. Tone

9/4/2002 7:45 AM

Tony@Mastertone

What effects inductance

As you may have noticed... I have been asking a few simple questions and asking for everyones input so the not so experienced guys can soak up the info, as sometimes when your new to something you just dont know what questions to ask....

So.... in everyones opinion, (please, without going into rocket science)...

1. What effects inductance???? and

2. How does this relate to output and tone???

i.e. Is it a mechanical relationship, electrical.. or a combination of both etc..

Tone

9/4/2002 1:20 PM

Dr Strangelove

Tony wrote:

quote:
"So.... in everyones opinion, (please, without going into rocket science)... "

Und vaat iss wrrrong mit rrogget zcienze?

-drh
--

9/4/2002 1:34 PM
SK	Oy Vey, I'll put in my $.02 but it's pretty "uneducated"... IMO Inductance is THE MOST USABLE measurement I can make with my LCR meter. I find it much more directly related to output strength than DC resistance as it seems to account for the difference in wire guages. Seems to be pretty much purely mechanical (although it is affecting electrical). Capacitance seems to indicate a bit more about the tone... Of course, there are so many other factors in play that any or all of the measurements are just rough indicators...

9/4/2002 1:34 PM

Oy Vey, I'll put in my $.02 but it's pretty "uneducated"...
IMO Inductance is THE MOST USABLE measurement I can make with my LCR meter. I find it much more directly related to output strength than DC resistance as it seems to account for the difference in wire guages. Seems to be pretty much purely mechanical (although it is affecting electrical). Capacitance seems to indicate a bit more about the tone...
Of course, there are so many other factors in play that any or all of the measurements are just rough indicators...

9/5/2002 9:28 PM
Tony@Mastertone	Come on you lot... Is everyone shy or something... Tone

9/6/2002 2:52 PM
Dr Strangelove	How meaningful is it to characterize a guitar pickup as a passive component, a lumped network of resistances, inductances, and capacitances? Since a pickup transforms on kind of energy into another, I suspect it's called a transducer. Microphones and loudspeakers can be characterized by their impedance charts, and these things are useful as far as they go, but they aren't the whole story. Pumping an electrical signal through it like a resistor hooked to a meter won't give the same results as when you magnetically induce a signal in it. I'll let you know if I come up with a test that uses a few wires and a PC sound card. -drh --

9/6/2002 2:52 PM

Dr Strangelove

How meaningful is it to characterize a guitar pickup as a passive component, a lumped network of resistances, inductances, and capacitances?

Since a pickup transforms on kind of energy into another, I suspect it's called a transducer.

Microphones and loudspeakers can be characterized by their impedance charts, and these things are useful as far as they go, but they aren't the whole story.

Pumping an electrical signal through it like a resistor hooked to a meter won't give the same results as when you magnetically induce a signal in it.

I'll let you know if I come up with a test that uses a few wires and a PC sound card.

-drh
--

9/11/2002 6:53 PM
Doc	Re: What effects inductance Inductance is related to the diameter of the coil, and number of turns in series. If there is a permeable magnetic material at the center of the coil, it increases inductance greatly over that of an air core coil. The basic effect you will notice with guitar pickups, with regard to inductance, is that as the coil's inductance is increased, the peak resonant frequency decreases. More turns on the coil will increase the voltage output, but will at the same time reduce the peak resonant frequency. The pickup will be stronger, but not as bright as a similarly constructed pickup with fewer turns. Chris Kinman seems to be the one who has the best handle on inductance versus overall frequency response & tonality of pickups. The mass of the magnetic core substance (size of the polepiece magnets or iron) greatly affects the pickup's inductance. There seems to be a delicate balance between coil turns, coil geometry, and magnet mass. It's a complex system. A single coil pickup that is fairly narrow & tall (vintage Stratocaster) has a lower inductance and higher resonant frequency, brighter overall tone, than a wider & flatter coil (P90) which has been wound with the same number of turns. Other parameters matter, but this should give you a general feeling for the inductance portion.

9/11/2002 6:53 PM

Doc

Re: What effects inductance

Inductance is related to the diameter of the coil, and number of turns in series. If there is a permeable magnetic material at the center of the coil, it increases inductance greatly over that of an air core coil.

The basic effect you will notice with guitar pickups, with regard to inductance, is that as the coil's inductance is increased, the peak resonant frequency decreases. More turns on the coil will increase the voltage output, but will at the same time reduce the peak resonant frequency. The pickup will be stronger, but not as bright as a similarly constructed pickup with fewer turns. Chris Kinman seems to be the one who has the best handle on inductance versus overall frequency response & tonality of pickups. The mass of the magnetic core substance (size of the polepiece magnets or iron) greatly affects the pickup's inductance. There seems to be a delicate balance between coil turns, coil geometry, and magnet mass. It's a complex system.

A single coil pickup that is fairly narrow & tall (vintage Stratocaster) has a lower inductance and higher resonant frequency, brighter overall tone, than a wider & flatter coil (P90) which has been wound with the same number of turns.

Other parameters matter, but this should give you a general feeling for the inductance portion.

9/11/2002 10:17 PM
Frank DeSalvo	Guesstimating the inductance of a length of wire and its return path, or of a wire loop can be done by applying a useful rule-of-thumb. This note provides a brief theoretical background in order to get order-of-magnitude estimates of wiring inductance, and points the user to several references that can be used if more accurate results are needed. The bottom line is that a wire loop has approximately 0.5-1 microHenries of inductance per meter of length, depending on the wire-wire spacing, wire diameter, shape of the loop, etc. For wire spacing large compared to the wire diameter, the inductance of the loop is a weak function of wire diameter (which makes physical sense, if you think about it). For instance, a circular loop of wire with loop radius a and wire radius R has the approximate inductance [Wheeler]: Lo = mu_not[ln(8a/R) - 2] Using this formula, the inductance of a 1 meter circumference loop of 14 gauge wire is 1.07 microH; for 16 gauge wire it's 1.12 microH; and for 18 gauge wire it's 1.16 microH. Note the weak dependence of inductance on wire diameter. This is due to the natural log in the expression. So our guesstimate of 0.5-1 microH per meter of length is a pretty good starting point. A crude approximation to the Wheeler formula for circular loops is L = munotpia [Lee, pp. 56] which predicts an inductance of 0.63 microH for a 1 meter circumference wire loop. My kg moment... ~F

9/11/2002 10:17 PM

Frank DeSalvo

Guesstimating the inductance of a length of wire and its return path, or of a wire loop can be done by applying a useful rule-of-thumb. This note provides a brief theoretical background in order to get order-of-magnitude estimates of wiring inductance, and points the user to several references that can be used if more accurate results are needed. The bottom line is that a wire loop has approximately 0.5-1 microHenries of inductance per meter of length, depending on the wire-wire spacing, wire diameter, shape of the loop, etc. For wire spacing large compared to the wire diameter, the inductance of the loop is a weak function of wire diameter (which makes physical sense, if you think about it).

For instance, a circular loop of wire with loop radius a and wire radius R has the approximate inductance [Wheeler]:

Lo = mu_not[ln(8a/R) - 2]

Using this formula, the inductance of a 1 meter circumference loop of 14 gauge wire is 1.07 microH; for 16 gauge wire it's 1.12 microH; and for 18 gauge wire it's 1.16 microH. Note the weak dependence of inductance on wire diameter. This is due to the natural log in the expression. So our guesstimate of 0.5-1 microH per meter of length is a pretty good starting point. A crude approximation to the Wheeler formula for circular loops is L = munot*pi*a [Lee, pp. 56] which predicts an inductance of 0.63 microH for a 1 meter circumference wire loop.

My kg moment...

~F

Page 1 of 2

Next>

Last Page>>