DC Resistance equals output???

Discussion in 'Just Pickups' started by Antigua Tele, Feb 7, 2018.

  1. Antigua Tele

    Antigua Tele Friend of Leo's

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    Maybe so! Since this scatter plot analysis suggests that DC resistance is a reasonably close indicator of inductance when the wire gauge is normalized, and because DC resistance is directly related to wire length, it means that you can fairly reliably trace a line from one to the other.

    When people say a pickup is "hot", it means two things: louder and darker. The darker part comes from the inductance, because a pickup is an LC low pass filter, and a higher inductance "L" means a lower pass. As for louder, every turn of wire on the coil is like a single AC generator, so if you have 8,000 turns of wire, it's as though have have 8,000 AS generators producing a voltage in series, which all adds together, in the same respect that two 1.5 volt batteries in series gives you 3 volts, three give you 4.5 volts, etc. The number of little AC generators you have in series corresponds to the amount of wire, which corresponds to DC resistance (a critical caveat is that not every loop of wire produces the same voltage, the loops closer to the guitar string produce more voltage than those which are farther away).

    The catch is that the number of winds on the coil is not the only factor that determines voltage and inductance. The output voltage and inductance are also effected by the core materials, and the voltage specifically is effected by magnetic strength and coil geometry, but that only means we can't compare pickups that are of a significantly different types. If you have two Stratocaster single coils with AlNiCo 5 pole pieces, or two P.A.F. pickups with identical dimensions, then nearly all of those additional factors are the same, and therefore cancel out on both sides of the equation. Chances are, you're probably comparing pickups of a given type to being with. So if you have two Strat pickups, and one has a DC resistance of 6.0k, and the other 6.5k, the inductance, and therefor the "hotness", will track closely with the difference in DC resistance. Also note that while DC resistance is linear as more wire is added to the coil, inductance rises exponentially, so the "hotness" difference between a 5.5k and 6.5k Strat pickup is smaller than 6.5k up to 7.5k, which is smaller than 7.5k to 8.5k, etc.

    The major practical problem with associating DC resistance to the hotness of a pickup is that not all pickups are wound with the same wire gauge. Most all pickups are wound with 42AWG, but many pickups, such as Tele neck pickups, are wound with the finer 43AWG, and many high output humbuckers are wound with even finer 44AWG. The finer wire will show a higher DC resistance for the same length of wire. So if you're comparing two Strat pickups, and one is wound with 42AWG while the other is 43AWG, it's apples and oranges. Fortunately, that can be accounted for by converting the actual DC resistance of one wire gauge to the relative DC resistance of another. Then it's apples to apples again.

    This PDF offers values for resistance per foot of these different guages of copper wire http://mwswire.com/wp-content/uploads/2016/10/techbook2016.pdf

    Here is the good part:

    [​IMG]


    There's only three values here that are needed 1659, 2143 and 2593 ohms, the nominal resistance for 42, 43 and 44 AWG. The min and max suggest the margin for error, although it's not apparent here the degree to which copper wire deviates from the nominal value.

    Therefore...


    To convert 42 AWG to 43 AWG equivalent, you multiply the resistance by 1.29 ( 2143 / 1659 )
    To convert 42 AWG to 44 AWG equivalent, you multiply the resistance by 1.56 ( 2593 / 1659 )

    To convert 43 AWG to 42 AWG equivalent, you multiply the resistance by 0.77 ( 1659 / 2143 )
    To convert 43 AWG to 44 AWG equivalent, you multiply the resistance by 1.21 ( 2593 / 2143 )

    To convert 44 AWG to 42 AWG equivalent, you multiply the resistance by 0.64 ( 1659 / 2593 )
    To convert 44 AWG to 43 AWG equivalent, you multiply the resistance by 0.83 ( 2143 / 2593 )


    One practical use of these conversions if determining just how much hotter an "overwound" 43 AWG bridge pickup is than it's 42 AWG normal wind neighbors. Take the Antiquity II for example, the "hot bridge" has a DC resistance of 10.08k with 43 AWG whereas the neck and middle have DC resistance of 6.44k with 42AWG. So what would the DC resistance be for the hot bridge if it were 42 AWG? 10.08k * 0.77 = 7.76k. Could the hot bridge actually be wound with 44AWG? If the "hot bridge" were wound with 44AWG, the 42AWG equivalent would be 6.4k, which is the DC resistance of the neck and middle pickups, but because we know the "hot bridge" has a much higher inductance than the neck and middle, and is in fact "hotter", it's not possible that 44AWG has been used.

    The real tricky business might be determining what wire gauge a coil is wound with. The "default" is 42AWG for most all "vintage" Fender and Gibson pickups. In general, when a Fender single coil has a DC resistance over 8k ohms, the higher DC resistance suggests that it's bumped down to 43AWG. For a P.A.F. style humbucker, the cut off from 42AWG is somewhere between 9k and 10k ohms, as this is the point where the bobbin becomes "full" with 42 AWG, necessitating smaller 43AWG wire. The corresponding cutoff mark for 43AWG is harder to pin down, but if the DC resistance is over 15k ohms, odds are it's that even thinner 44AWG wire being used. In the case of P-90's, because they have such a large bobbin, most all are wound with 42AWG, despite reaching a DC resistances beyond 10k with just one coil.

    If you're shopping for pickups, and all the pickup maker is offering are DC resistance values, these considerations and calculations can help you determine how their product compares to others, despite of the scant technical information provided.
     
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  2. Rob DiStefano

    Rob DiStefano Doctor of Teleocity Vendor Member

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    ALL of the above can be simply stated that passive single coil pickups work this way ...

    for a given bobbin footprint and height (a pickup's physical design and shape), and a given coil wire diameter and insulation, the lower the coil wire turn count, the greater the treble and the lower the output - the higher the coil wire turn count, the greater the midrange, the greater the output and the lower the treble.
     
  3. Asmith

    Asmith Friend of Leo's

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    The whole reason people argue you can't look at dc resistance to determine inductance/output is that it can be misleading but it doesn't dispute the trend they form it just says it's not a strong correlation when you apply it to all pickups without taking anything else into consideration.

    The first graph including every data point shows a correlation but it's not a very strong one, the spread of the DC resistance vs loaded frequency is massive. When you take the wire gauge into account things get a lot neater but that's the argument; DC resistance means very little without knowing the wire gauge.
     
  4. Rob DiStefano

    Rob DiStefano Doctor of Teleocity Vendor Member

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    yes indeed. dcr only has meaning when comparing like apples to like apples. changing the coil wire gauge, or changing the coil wire winding tension, or changing coil wire insulation values, or taking dcr readings at different coil and ambient temperatures, will all affect a dcr reading. dcr has its place, but not the high pedestal the music industry lauds it. it's all marketing nonsense to make sales, let alone obfuscate the truth about a product.
     
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  5. CFFF

    CFFF Tele-Holic

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    I see DCR as a steering factor. The greater the DCR the more inductance. More inductance does mean less treble. Historically I have avoided high output, or high DCR pickups but in recent years I have discovered 15k humbuckers that were surprisingly useful to me and I like a more jazz tone. Often, pickup makers and sellers will only list DCR values anyway. Some do not even give you that. But if they all gave more detailed information such as plotted resonant peaks/loaded-unloaded db values, magnet type/gausse graphs, inductance and capacitance readings, wire gauge/enamel type/ spacer bar/slug/cover/baseplate material, the average potential buyer might run a mile. They do not wish to be confusicated by science. ******** is what sells and this is what I believe the majority of buyers are, maybe unknowingly looking for when shopping for new and replacement pickups anyway. They are not interested in being educated. If they are told those pickups are genuine vintage spec and will sound just like Jimi or whoever that is all they need to know and the more that they cost the more they will be appreciated. Just don't pitch them higher than the price of the latest iPhone incarnation. They are not all stupid.
     
  6. jamieorc

    jamieorc Tele-Holic

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  7. Asmith

    Asmith Friend of Leo's

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    When it comes to buying pickups (that I have previously not heard) I would at least like to see a bass, mid, treble and output graph a number like 15k DCR just means it's resistance is 15k. At that point you can assume the gauge wire is at least 43 or 44 AWG but the difference between the two wires (given the DCR) will change the inductance. We haven't even touched capacitance yet which is the other major factor that will change your tone greatly.
     
  8. Antigua Tele

    Antigua Tele Friend of Leo's

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    About 60% of my post is specifically about addressing wire gauge, hence the comparison table. I even used the term "apples to apples".

    As I was saying in the first paragraph, the fairly tight correlation between the inductance and the DC resistance show that while these factors can confound assumptions, they're not as big of a deal as people might think.

    I don't disagree, but it's not as useless as people like Bill Lawrence and many others make it out to be, either. It doesn't "tell you as much about a man's shoe size and his intelligence". Maybe if Bill Lawrence had seen that scatter plot he would have though differently, for example.
     
    Last edited: Feb 7, 2018
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  9. Antigua Tele

    Antigua Tele Friend of Leo's

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    As I had said in the OP, most all pickups use 42 AWG, and there are ways to make an educated guess as to when 43 and 44 AWG are being used, and that conversion table can be used to make them into like-units. So there again, it takes some careful thought, but it's not hard to work around.
     
  10. Antigua Tele

    Antigua Tele Friend of Leo's

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    Actually it doesn't. 8000 turns of 42, 43 and 44 AWG all give you nearly identical inductances. I neglected to go into that level of detail for brevity, but that's a happy fact that makes DC resistance a surprisingly useful metric. Had this not been the case, we'd be SOL.

    I also neglected to mention this for brevity, but capacitance matters very little because a) the guitar cable alone supplies more that three times the overall value, and b) for a given type of pickup, the capacitance tend to be very closely clustered. A pickup is primary an inductor, the capacitance is merely parasitic and so there is a lot less of it, comparatively speaking.
     
  11. Smiff

    Smiff Tele-Holic

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    Love these threads lol. Electrical Engineering is dark arts to me but I appreciate your calcs and reasoning @Antigua Tele. You seem to be the main pickup man.

    Perhaps not the right place; but I’ve seen a set of Tele pickups I like that are both 6.4K and 42 AWG. I assume they both have the same length of wire to achieve this, so the bridge bobbin is proportionally emptier than the neck bobbin for want of a better phrase. Is that right? How balanced would this set be? I understood that the neck is often a higher output because it’s smaller and has a cover. Could the neck in this set be a higher output with stronger magnets or something?
     
  12. 3-Chord-Genius

    3-Chord-Genius Poster Extraordinaire

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    What's funny is that I stopped playing guitar for almost 10 years. When I got back into it again, the two new major developments I noticed were: 1) digital modeling, and 2) the resistance of pickups now being a big deal.
     
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  13. BorderRadio

    BorderRadio Poster Extraordinaire Silver Supporter

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    My TV Jones Starwood Telecaster bridge pickup is one of the best I've heard to date. It's very clear, strident, strong enough to keep up with the bass-heavy neck Dynasonic. It is not very dark or overly middy. The Starwood has a resistance reading of 12K, inductance stated at 4.0H. Don't know the wire gauge but I assume it's around 44AWG. By the conversion factors above, this means it's 'like' a regular 42AWG 7.7k bridge pickup, though coil geometry is different, and don't forget the fat Alnico slugs.
     
  14. Smiff

    Smiff Tele-Holic

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    I never stopped playing but went a similar length of time not looking at or buying new gear and noticed that when I started going online to research for my build.

    I got some cheapish pickups for my Strat more than a decade ago and they were ‘vintage pickups’ or something and that was it. Nowadays Fender do several pickups which would fit that ‘vintage pickup’ description but they all vary in spec and output so it’s good to know what sort of vintage output they have I guess.
     
  15. Antigua Tele

    Antigua Tele Friend of Leo's

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    You can't compare Tele neck and bridge pickups as easily, because the bobbins are different shapes. The pole spacing of the Tele bridge is about 7mm wider than the neck, so thats more wire per turn.

    Another thing to note is that AlNiCo 2,3 and 4 will will cause a higher inductance than AlNiCo 5, because AlNiCo 2,3 and 4 have a higher permeability, so if you're comparing the DC resistance of an AlNiCo 3 pickup and an AlNiCo 5 pickup, you'd want to imagine there's about an extra 0.3k to 0.6k ohms of wire on the bobbins. Take the Seymour Duncan Antiquity I and II for Strat as an example; they have about the same DC resistance, but the Ant. I uses AlNiCo 2 and shows 2.9H inductance, where as the Ant II uses AlNiCo 5 and only shows 2.5H inductance. It's hard to say how much wire gets you 400mH difference because DC resistance is linear, where has inductance rises exponentially, but as a rule of thumb, 0.3k to 0.6k ohms.
     
    Last edited: Feb 7, 2018
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  16. Antigua Tele

    Antigua Tele Friend of Leo's

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    That all sounds about right.

    An interesting thing about those large slugs is that they're not really any stronger than smaller sized slugs, and I know this from having looked at the Seymour Duncan Quarter Pound, they make the AlNiCo pole piece wider, but not longer, and because AlNiCo has a low coercivity, if the pole piece is too short relative to it's face, the magnet starts to fight against itself. That's why your typical Strat pole piece or humbucker bar magnet has a length that is approximately four times greater than the width of the polar faces. In fact, I measured a lower Gauss reading at the top of the Quarter Pound magnets (800G) than I do a typical A5 rods (1050G). But they look cool, and have a cool name!

    I've never looked at the Starwood, but TV Jones is asking $120 for the bridge pickup alone. No thanks.
     
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  17. Antigua Tele

    Antigua Tele Friend of Leo's

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    I went for about five years without buying a new guitar, and then I discovered Fender Japan, and also found that the quality of Epiphone and Fender Mexico has shot way up over the past decade. The fact that these are great guitars that come loaded with forgettable pickups is a big part of what got me into investigating them. I went looking for replacements and found a whole lot of this kind of thing...

    [​IMG]

    Gibson / Epiphone have really changed the game with their Probucker line, they're premium pickups. However Fender continues to fuel the pickup trade by putting ceramic/steel pickups in just about any guitar priced below $700. The Squier VM and CV series from China and Indonesia are coming loaded with AlNiCo pickups, Tonerider or "Duncan Designed", so they're doing better.
     
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  18. Smiff

    Smiff Tele-Holic

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    Yeah there’s some snake oil alright. I had some cheap unbranded Toneriders or at least Tonerider spec from the same factory (the description was a bit smoke and mirrors) and they were really good sounding. Sometimes more boutique brands make me feel like I have more credibility as a guitarist though :lol:
     
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  19. BorderRadio

    BorderRadio Poster Extraordinaire Silver Supporter

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    Yeah, well they are TVJs, so you know they're charging for the engraved flatwork :D I tried a few 'standard' Tele bridge pickups to best match the Gretsch Dynasonic that has the wider and longer Alnico rods. I even started a thread on this forum. The deal with the Dyna was having lots of bass, pretty Strat-like but just 'more' or louder. Since I didn't want the magnets hanging out the back of the guitar I couldn't take it down any lower. I gave in to TVJ after trying a couple of recommendations, and it worked best. Maybe a Fender Blackguard would have worked, but that didn't hit my radar.

    When are you going to compare Vintage DeArmond 'Fidelatone' models to modern Dynasonics and T-Armonds?
     
  20. Smiff

    Smiff Tele-Holic

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    Is there a point where low output just sounds rubbish? How low can you go?

    I’m well into the idea of them at the moment, I only ever play electric for volume really, always clean so I don’t need a high output to push my amplifier into overdrive or anything. I assume lower output = cleaner sound?

    The lowest I’ve seen is about 5.5K without going boutique custom wind.
     
    Last edited: Feb 7, 2018
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