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#42 vs. #43 -- e.g., number of turns vs. DCR

5/17/2006 12:56 PM
#42 vs. #43 -- e.g., number of turns vs. DCR
I've known for some time that DCR readings are not the ultimate in guaging a pickup's output and tonal parameters -- many, many other factors (magnet type and size, polepiece length and head-size, coil shape etc.,) come into play, not the least of which is the temperature of the room or outdoors or wherever the pickup is when you take the reading.  
But I've had my suspicions for some time that the DCR readings on pickups with #43 are even more deceptive because it takes fewer turns of #43 to reach a given DCR level than #42 (not to mention the smaller size of a #43 coil reducing the amount of bass which further reduces output).  
Anyway, because MWS Wire puts ohms-per-foot specs on their spools, I've been able to come up with a sort of "Celsius to Farenheit" conversion formula that seems to give a decent ballpark figure for translating #43 wire DCR readings to #42 wire equivalents -- at least it makes sense to my ears anyway -- and wanted the Collective's thoughts on it.  
My #42 spools say 1.770 ohms per foot while my #43 spool says 2.305 per foot. Presumably that's at room temperature, plus I'm sure it also varies slightly with how much the wire in the spool was or wasn't stretched, etc. But let's go with it...  
The DCR ratio of #42 to #43 is then about 76.7%. Also trying to account for the smaller size of an equal-DCR #43 coil to a #42, I dropped the figure to a round 70%. Not exactly scientific and probably the weakest link in my chain of reasoning and I have a feeling that it should probably go even lower than 70% -- but again, let's go with it for now and you all can pick it apart in your replies.  
By this formula, and assuming all other factors (magnet type, etc.) are the same, the following would be a conversion of a 14k #43 wire pickup:  
14k x 0.7 = 9.8k  
A 14k humbucker with #43 wire would sound output-wise roughly like a 9.8k #42 wire pickup.  
Gentlemen, your mission is to help my to refine this formula further for more accurate conversions...
5/17/2006 2:43 PM
Wolfe Macleod
Don't forget to factor in tension differences.
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5/17/2006 2:11 PM

Tension will make a difference too, yes, because higher tension will jack up the DCR a little. But I wonder, Wolfe, help me out on this -- wouldn't the higher tension also mean the average length of wire per turn would be a little shorter (making a shorter overall coil wire length) and therefore it might cancel out some of that increase?  
Another thing is the geometry of the wind itself. A pickup with a shallow pitch will have a shorter overall wire length on the same number of turns than one with a steep pitch or heavy scatter, so the shallow pitched one will read lower.  
There's all kinds of stuff to factor in, which is why I'm just trying to get ballpark -- a ratio precise out to the 5th decimal point is an impossibility.
5/17/2006 2:48 PM
Wolfe Macleod
Well..sort of. Increasing the tension stretches the wire making it longer as you know...if you wrap that increased tension around the coil and then remove it, the overall lenght should be shorter than a low-tension wrap. Theoretically. If is springs back to it's original lenght.  
You are correct in the shallow pitch having shorter turns, yes - less bobbin lenght to traverse - shortest distance between two points is a straight line... But I think the difference in lenght is not that noticable. I prefer a wide pitch, myself. Very rarely do I make a pickup with a pitch more than 30 or 40 Turns per layer.
5/17/2006 3:11 PM

I don't like the turns close either -- tried that once and came up with a humbucker that could cut glass. I'm a crazy-scatter man myself.
5/17/2006 4:01 PM
jasin lollar

Then you have coil geometry- like a strat verses a P-90 which will entirely throw off your rough metod of determining turns.
5/17/2006 4:09 PM

Yes, but remember that I'm controlling for all that -- remember, same magnet type/size, same polepiece size/shape, same pickup type. That would include eliminating comparisons of bobbins with radically or significantly different shapes and sizes.  
In other words, this formula is NOT intended for comparing the output of, say, a #43 wire Tele rhythm pu with a #42 wire humbucker or P90. They're apples and lemons to begin with.  
You CAN use it to compare a #43 wire Strat with a #42 wire Strat...or a #43 wire P90 with a #42 wire P90....etc.
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