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 Post subject: help with comparing pickup output
 Post Posted: Tue Oct 13, 2015 9:09 am 
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Joined: Thu Jun 04, 2009 3:15 am
Posts: 674
Location: Florida
hi,

how do I measure the OHMS or whatever it is that tells me the relative output of each pickup in my 1966 370-12 MG? Yes I understand they will not be exactly the same per pickup.

why I ask? it seems like the center pickup is louder than the bridge or neck pickups, but I know for a fact they have never been changed or replaced. Could the other two pickups be degraded? It is an old guitar.

OR: could this have anything to do with the mod I made?

(I made a new bottom pickguard, installed 3 on-off mini-switches, 1 Tone and 1 Volume pots, nothing else. I did it like that because I wanted every possible pickup combination, and I don't care for individual volume and tone controls for each pickup, a Master volume and Master Tone is fine). I purchased the parts kit from Carvin.

Thanks for any tips. I do have an ohmeter.


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 Post subject: Re: help with comparing pickup output
 Post Posted: Tue Oct 13, 2015 6:52 pm 
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Joined: Sat Nov 22, 2008 6:58 am
Posts: 84
Location: Michigan
The easy way to measure the ohms of this type of a pickup is to plug in a cord, select that pickup only, volume full up, and measure it at the other end of the cord. Its not as accurate as removing the pickup from the circuit to measure, but its close enough for a quick check.


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 Post subject: Re: help with comparing pickup output
 Post Posted: Wed Oct 14, 2015 3:49 am 
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Joined: Thu Jun 04, 2009 3:15 am
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Location: Florida
thank you Steve.

is this check done with a ohmeter?


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 Post subject: Re: help with comparing pickup output
 Post Posted: Wed Oct 14, 2015 5:53 am 
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Measuring the DC resistance of a pickup does not tell you its output in millivolts or its tonal characteristics as to its resonant peak. All it does is give you an estimate of how many turns of wire are on the pickup, if you know what wire at what tension the bobbin is wound with.

There are way too many variables: bobbin, magnet type, strength and configuration, pole piece variables, etc. Even the wire can have some variation from spool to spool, although that is slight and very tightly controlled. And finally, the values of the pots and tone caps will have an effect as well on the tone by just being wired into the circuit (what we informally call loading), even if all the controls are dimed out.

That said, here is the general rule: give the same bobbin, magnets, polepieces and wire wrapped at the same tension, then more turns will have slightly greater output, slightly higher mids from increased inductance and lowered resonant peak, and slightly less highs from intra-coil capacitance. By contrast, again, given all else being equal, less turns will have slightly less output, slightly lower mids from lower inductance and raised resonant peak, and slightly more highs from less intra-coil capacitance.

So, you cannot just automatically assume how two given pickups will differ in tone in terms of its resonant peak or output in millivolts to drive the front end of an amplifier with a given setup just because one pickup reads a different DC resistance measured from the pickup's hot lead to the meter. And likewise, if the other variables are different, you cannot tell what a pickup will sound like just because it may have the same number of turns of wire on the bobbin, and therefore the same DC resistance measured from the hot lead of the pickup, as another pickup.

And then there is the effect on the overall inductance of the pickup whether you use alnico or ceramic magnets, and how they are configured, and the articulation differences from having polepieces on high gains, slugs on toasters, or blades on the HB-1's, and.... (I hope you're getting the picture.)

On one of my old instruments, lowered output on one pickup was directly attributed to the magnet losing solid contact with the pole pieces. When that was fixed, the pickup and the instrument sounded as it should.

If you are going to all that you are to modify your instrument, and the center pickup is noticeably louder, then simply swap the bridge and center pickups. The bridge position, with less string excursion over the pickup than the center or neck position, will benefit from the stronger output of the pickup since less signal is being induced into the pickup from the vibrating string, and you may restore perceived balance that way.

Also note that because the center pickup is roughly where many players pick, there will be a stronger articulation over that pickup, which may be perceived as a stronger pickup overall.

Also note that the pickup height is critical, because the signal level induced by the string vibrating over the pickup varies as the square of the difference in height, not simply linearly. So just the slightest difference in pickup height or string clearance can make a noticeable difference in output.

Traditionally, keeping the top paragraphs in mind, many players, if their instrument has the same make and model of pickup in all positions, position the pickups with the one with the highest DC resistance, meaning the most turns of wire on the bobbin, in the bridge position, and the one with the lowest DC resistance, meaning the least number of turns, in the neck position. But again, if there is something inconsistent internally to the pickup, that is not always the case. I personally don't do that. Between twenty and thirty years ago I had an instrument of another make that even though one pickup had more windings on it than the other, the magnet was stronger in the pickup with slightly less windings, and had a stronger, brighter tone, so I installed it in the bridge position to counter the guitar's naturally heavier tone, and give clarity, even with less output, to the neck position. I also don't do that on a Rickenbacker instrument, because too many windings result in too thick of a tone, depriving jangle, in the bridge position.

Forgive me saying it, but by rewiring, you gave up the best solution to the balance issue: the stock fifth knob.

To conclude, there are a lot of items to consider in evaluating the pickups and setting up the instrument other than a raw DC ohmmeter reading.


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 Post subject: Re: help with comparing pickup output
 Post Posted: Wed Oct 14, 2015 6:31 am 
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I ran out of time. The "Traditionally" paragraph should read:

Traditionally, keeping the top paragraphs in mind, many players, if their instrument has the same make and model of pickup in all positions, and in order to achieve perceived balance, position the pickups with the one with the highest DC resistance, meaning the most turns of wire on the bobbin, in the bridge position, and the one with the lowest DC resistance, meaning the least number of turns, in the neck position. But again, if there is something inconsistent internally to the pickup, that will not always address the issue. I personally don't do that. Between twenty and thirty years ago I had an instrument of another make that even though one pickup had more windings on it than the other, the magnet was stronger in the pickup with slightly less windings, and had a stronger, brighter tone, so I installed it in the bridge position to counter the guitar's naturally heavier tone, and give clarity. The other pickup was a nice contrast with its slightly mellower tone and less output in the neck position. I also don't do that on a Rickenbacker instrument, because too many windings result in too thick of a tone, depriving jangle, in the bridge position.


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 Post subject: Re: help with comparing pickup output
 Post Posted: Wed Oct 14, 2015 8:38 pm 
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Joined: Sat Nov 22, 2008 6:58 am
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Location: Michigan
Thanks for all the pickup info. There's a lot more to it than just DC resistance.


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 Post subject: Re: help with comparing pickup output
 Post Posted: Thu Oct 15, 2015 5:58 am 
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Joined: Thu Jun 04, 2009 3:15 am
Posts: 674
Location: Florida
thank you Steve and iiipopes for all the information, obviously there is more to the issue than just measuring ohms.

the option to invert the middle pickup with the bridge pickup is a good one. It should let me know if my perception is correct.

as to the Blend knob, I've never used the Rick-O-Sound, always connected the guitar to the mono jack, so the Blend knob was never used. Also I did not "eliminate it" as such, I simply removed the entire controls assembly and lower piclguard, unsoldered the jack wires from it, and put it away safely, then mounted a new lower pickguard with new controls soldered to the two mono jack wires. It can be reverted to original since I made drawings and notes as to where the original jack and pickup wires were soldered to. I was very detailed.

As to pickup height adjustment, there isn't much if any, the pickups sit on the top with those tiny rubber grommets, and the center screw just fastens the pickup to the top. I suppose the tighter the center screw, the lower the pickup will go, but we're not even talking 1/16th" inch adjustment up or down.


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 Post subject: Re: help with comparing pickup output
 Post Posted: Thu Oct 15, 2015 4:02 pm 
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Joined: Thu Dec 15, 2005 2:00 pm
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Location: Los Angeles area
iiipopes, thanks for your good information on resistance and measuring same and the variables involved.


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 Post subject: Re: help with comparing pickup output
 Post Posted: Fri Oct 16, 2015 5:46 am 
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The fifth knob is not just a Ric-O-Sound feature. It is integral to the stock wiring of many models of both single output and Ric-O-Sound instruments. Go look at the specifications pages, especially the 320/325/330/340/350/380/381/620/660 guitars and their derivations.


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 Post subject: Re: help with comparing pickup output
 Post Posted: Tue Oct 20, 2015 9:23 am 
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Joined: Thu Jun 04, 2009 3:15 am
Posts: 674
Location: Florida
in my guitar, the blend knob never did anything unless the guitar was connected with a stereo cable??

Going to take some pictures of the original 1966 controls/pickguard assembly and post them here as soon as I have them.


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