PUP Impedence VS Tone

Fred Nolen · From: Mohawk, Tennessee, USA

PSG pickups are normally wound to anywhere between 16.5 and 21 Kohms. What is the net result in the differences as they relate to highs, mids, and low frequencies?

Thanks,

Ol' Fred

Bob Hoffnar · From: Austin, Tx

With all things being the same the simple way to look at it is the higher the impedence the darker and louder the pickup is. So a low impedence like 14K will be briter and not as loud or full sounding as a 20K one.

The relationship between capacitence and inductance will bring out a certain frequency range. I think its called a Q point or something like that. So different pickups will suit some guitars and personal tastes better than others.

Bill Lawrence pups have a very high impedence and are much briter sounding than some other brands low impedence pups. It gets pretty weird.

I deal with this stuff quite a bit and basicly trust my ears.

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Bob
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Dave Mudgett · From: Central Pennsylvania and Gallatin, Tennessee

The "impedance" you are talking about is actually the DC resistance. It increases if one uses thinner magnet wire or one increases the number of turns of wire. The complex impedance, which is a combination of resistance R, inductance L, and capacitance C, changes when the number of turns increases, which is the usual way pickup resistance is increased. Complex impedance changes with frequency, which is why the same exact pickup sounds different if the number of wire turns is changed.

As Bob said - all other things being equal, as the DC resistance is increased, the pickup generally tends to sound darker. But to go a little deeper, as the number of windings is increased, coil inductance, capacitance, and resistance tend to go up together. The dominant pickup sound is heavily influenced by the center-frequency and shape of the coil resonance - the resonance is the "peak" in the frequency response. This shape, either sharply tuned or more flattened out, is determined by "Q"-factor of the coil, which is computed as (1/R)*sqrt(L/C). For example, see http://en.wikipedia.org/wiki/Q-factor .

As the number of windings increases, L/C tends to stay "roughly" constant, and the effect of the (1/R) term tends to dominate, and Q goes down. This flattens out the resonance, and the increased inductance impedes high frequencies more. This leads to a more midrangey and less bright-sounding pickup.

I view most of the Lawrence pickups as mid-impedance pickups. The DC resistance is fairly high by the standards of guitar pickups, but other aspects of pickup design are very different and the complex impedance is not high. In particular, the inductance is quite a bit lower, and high frequencies are transmitted better.

Even though I find it useful to understand some technical facts behind pickup design, I agree with Bob and rely on my ears to decide what I like.

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