Pickup impedance as an indicator of tone?

Over recent years, a shorthand has developed wherein vendors and dealers describe the output(s) of a vintage guitar’s pickups by their DC resistance, measured in Ohms.  I was discussing this with a group of fellow high-end collectors over a fine Burgundy lunch recently and I ventured the view that this was incomplete, poor science.

DC resistance is usually a pretty good measure of how many turns of wire there are in any given pickup.  This is important as pickups were typically wound semi-manually in those days and counting of turns was usually a pretty rough and ready affair.

Since most pickups were wound using the same gauge wire, DC resistance can therefore provide a good first indication of the likely relative hotness of a pickup compared to others of its exact kind, say amongst P90’s on late 50’s Les Paul Juniors, for example.

But that’s about as far as it goes, because a number of other factors take over.  The first is gauge of wire used, which varies according to pickup make and design.  Then there’s the original and remaining strength of the magnets, which can vary wildly according to how the guitar was manufactured and where and how it has been kept.  And finally, there’s the chassis itself – the wood and the neck join.  Hence another collector obsession – weight.

In my experience, all of these factors make at least as much difference.  A couple of examples from my own explorations :

  • According to dealer lore, the DC resistance of my mint ’60 TV Junior’s single bridge P90 makes it medium-hot.  Yet it sounds fabulous, hot like Leslie West, and keeps up very well with my ’58 ‘burst for both volume AND TONE!  Acoustically, it’s a very live instrument, whereas the ‘burst has the typical, whilst not heavy, heavier-bodied response.
  • A ’57 stoptail Goldtop which once visited me sounded fantastic unplugged, but measured really low DC resistance and therefore didn’t promise much in terms of volume and tone.  But when it was plugged in – holy mother of God.  It wasn’t for sale, but if it had been… Yet I and I guess many others probably wouldn’t even have audtioned it on the basis of its advertised DC resistances alone!

Others’ views welcomed…

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