Pickups causing fret buzz

#22
Bruce Johnson said:
You got me curious, so I did a quick test. I grabbed one of my bench mules, which I use for testing pickups. It's 35" scale, with Chromes on it, up to standard pitch. I held a new 3/8" dia x 1" long A5 rod magnet near a string, right after the heel of the neck, moving it carefully closer to the string, while watching the movement of the string in relation to a fixed line. A 3/8" x 1" A5 is a big honkin' magnet, roughly 4 times the field strength power of a 1/4" magnet (like a Quarter Pounder) and roughly 8 times the power of factory Fender-style pickup magnet.

What I saw was this: With the magnet 1/8" (0.125") or more away from the string, I couldn't see any movement at all of the string. It was 0.001" or less. It didn't matter which gauge, which string. As I moved the magnet under 0.100" away, I could begin to see a little bit of movement, a few thousandths. When I got the gap down to about 0.050", the string would snap over and stick to the magnet.

So:
Yes, Chromes are not the most magnetic strings; steel rounds would be somewhat more magnetic.

But this was a really powerful magnet!

A gap of 0.100" between the magnet and the string at the 24th fret is not really even playable. Any plucking at all, and the string would stick to the magnet.

My conclusion from this is that any normal pickup would have to be unreasonably close to the strings to cause a few thousandth's of an inch of deflection from the magnet's pull.

A related observation about magnets vs strings: The conventional wisdom is that installing pickups with big magnets (like Quarter Pounders) will kill the sustain, because the powerful magnets will slow the strings down quicker. That's what everyone says. But, I can pluck the string on my test mule and listen to its decay, unplugged and unamplified. Pluck it again, and listen to the decay while holding the big magnet next to the string at the 24th fret, moving it as close as possible to the string without sticking to it. I tried, but I can't make the decay faster. And that's with the big honkin' 3/8" magnet held really close. So, how is a measly little Quarter Pounder slowing the string down, when it's normally further away than that?

I can answer that: The bigger magnets put a larger pulse on the beginning of the note- an exaggerated attack curve shape- before settling into the extended ring of the note. The overall volume (level) is louder, so you turn the level down to compensate. And your perception is that the sustain has dropped off. It's actually still there; you've adjusted in response to the big opening pulse.
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Bruce did you pluck the string when you put the magnet near it? If not then the experiment is not accurate.
 
#23
Like I said single coil J bass pickups with Alnico 2 magnets or weaker ceramic magnets do not seem to cause this problem. It is much stronger Alnico 5s and double coil magnets in the J bass neck position that cause the problem.
Bruce Johnson said:
Well, okay, I guess I can accept that, although the amount of deflection has got be very small. The string has about 30 lbs of tension in it, and the magnet has a few ounces of pull. How far is it going to pull the string off to the side? It wouldn't be hard to measure, but it's got to be less than 0.010".

So, accepting that the presence of the pickup's magnet is pulling the string down slightly, and you have your action set low enough that you are getting some buzz. Then you remove the pickup, which releases that downward pull, and the string goes slightly higher, stopping the buzz. By removing the pickup, you've effectively slightly raised the action.

The question becomes: Why don't you just put the pickup of your choice back in, and with it in place, slightly raise the action at the bridge saddles, until the buzz just stops? That would be putting the string at the same height above the frets, as you had previously gotten by removing the pickup, right? Why remove the pickup, when you could get the same net effect by turning the bridge saddle screws a little bit?
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No the string does not go slightly higher with the pickup out. Its when the string is in motion and goes through its rotation arc and passes near the pickup that the magnets pull the string slightly closer.
 
#24
F Brock said:
Like I said single coil J bass pickups with Alnico 2 magnets or weaker ceramic magnets do not seem to cause this problem. It is much stronger Alnico 5s and double coil magnets in the J bass neck position that cause the problem.

No the string does not go slightly higher with the pickup out. Its when the string is in motion and goes through its rotation arc and passes near the pickup that the magnets pull the string slightly closer.
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The magnets Bruce used in his experiment were stronger than Alnico 5s and/or double coil magnets. Sure, he was not able to replicate your situation, but the onus is on the person making the assertion to better account for how their assertion was not proven, not on those who successfully disprove it to account for why they themselves did not measure it. Experimental design tends to attempt to prove the "null hypothesis" which is basically that there is "no effect" or that the effect being produced cannot be unequivocally stated to be a direct result of the inferred effect. There was nothing wrong with Bruce's experimental design - it accounted for the main factors and used empiricist measurement techniques to determine variability.

With total respect to you, I think at this point, if you want to convince anyone of your assertion/assumption further, then the onus is on you to try to replicate Bruce's experiment on your actual bass, and demonstrate the null hypothesis is incorrect (i.e., that you are able to measure a difference in the string deflection differently than Bruce did, and secondly, show how there is not only fret buzz, but that it is due to the deflection). If you can do that, I will champion your cause and undoubtedly Bruce will also be interested, but just arguing the issue further with small details about the experimental design won't necessarily change the facts before us... :)
 
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#25
Beej said:
The magnets Bruce used in his experiment were stronger than Alnico 5s and/or double coil magnets. Sure, he was not able to replicate your situation, but the onus is on the person making the assertion to better account for how their assertion was not proven, not on those who successfully disprove it to account for why they themselves did not measure it. Experimental design tends to attempt to prove the "null hypothesis" which is basically that there is "no effect" or that the effect being produced cannot be unequivocally stated to be a direct result of the inferred effect. There was nothing wrong with Bruce's experimental design - it accounted for the main factors and used empiricist measurement techniques to determine variability.

With total respect to you, I think at this point, if you want to convince anyone of your assertion/assumption further, then the onus is on you to try to replicate Bruce's experiment on your actual bass, and demonstrate the null hypothesis is incorrect (i.e., that you are able to measure a difference in the string deflection differently than Bruce did, and secondly, show how there is not only fret buzz, but that it is due to the deflection). If you can do that, I will champion your cause and undoubtedly Bruce will also be interested, but just arguing the issue further with small details about the experimental design won't necessarily change the facts before us... :)
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Ok Beej. As you said " Bruce was not able to replicate your situation " . So when Bruce puts a Alnico 5 Double coil pickup in a bass with Nickel round wound strings in the J bass neck position and sets the string 1/4 away from the pickup with a medium low action then we can compare apples to apples. I guess the folks at Seymour Duncan, Bartolini, Dimarzio and EMG also must be suffering this same delusion and the conversations I had with them about this were just a dream.
 
#26
Bruce wasn't able to replicate your situation because instead, he proved the null hypothesis and showed that your situation was likely to have occurred due to other factors. With his magnet strength being higher than yours, and the distance from the string being less, the deflection should have been greater than what you found on your bass. In other words, although he did not replicate your experiment exactly, he did set it up so that any effects would have actually been greater in his experimental model, not less. Its not really comparing apples to oranges. Its more like comparing a 6 ounce apple to a 20 ounce apple. :)

Regarding others and their speculation, its best not to give too much credence to them. People in positions of "authority" are disproven by scientific evidence all the time - its how science moves forward. They aren't delusional, Bruce just demonstrated that their speculation was not backed up via empirical evidence. If we're going to make "appeals to authority" anyway, then it's probably worth mentioning that Bruce is an engineer and a professional luthier with many years of extensive experimental experience. I'm not an engineer and would not call myself a "luthier" but I am a research scientist and pretty comfortable with experimental design... :)
 
#27
Beej said:
Bruce wasn't able to replicate your situation because instead, he proved the null hypothesis and showed that your situation was likely to have occurred due to other factors. With his magnet strength being higher than yours, and the distance from the string being less, the deflection should have been greater than what you found on your bass. In other words, although he did not replicate your experiment exactly, he did set it up so that any effects would have actually been greater in his experimental model, not less. Its not really comparing apples to oranges. Its more like comparing a 6 ounce apple to a 20 ounce apple. :)

Regarding others and their speculation, its best not to give too much credence to them. People in positions of "authority" are disproven by scientific evidence all the time - its how science moves forward. They aren't delusional, Bruce just demonstrated that their speculation was not backed up via empirical evidence. If we're going to make "appeals to authority" anyway, then it's probably worth mentioning that Bruce is an engineer and a professional luthier with many years of extensive experimental experience. I'm not an engineer and would not call myself a "luthier" but I am a research scientist and pretty comfortable with experimental design... :)
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Wow. Thats all I have to say. Anyway thanks for the sparing contest.
 
#28
I am a Luthier. A very experienced one. I built all these basses. Including the Upright.
IMG_20160831_221609.jpg
 
#30
F Brock said:
Hi there,

Just finished building a 5 string bass and I am scratching my head with a strange fret buzz issue. I leveled the frets , strung the bass up and it played very well with a nice low action and no fret buzz. After putting the pickups in it started buzzing like crazy. Took the neck pickup out( pickups are in standard J bass position) and the fret buzz went away. Put a set of pickups in from a different manufacturer and still same problem. Bass has nickel would Ken Smith strings. I have set the pick ups very low ( to low ) and still the problem. Take the neck pickup out and the fret buzz disapears? Thoughts?
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Hi,
I know this is an old post but I would like to chime in on this. I have a custom 6 String bass that was made for me 4 years ago. Best bass I have ever owned and played. I have been playing for 35 years. It has EMG 45DC bridge pick up. My action is 2 mm on low B to 1.5 mm on high c string. .014 neck relief. That is low. I play with light attack. I use Dunlop Super bright 130-30 strings. I just had another EMG 45DC installed yesterday in the neck position. When I got the bass home I put new strings on and set the pick up height to 2 mm same as my bridge pick up.

When I played it for the first time my bass buzzed like crazy. Every fret. Low B and E string and some of the higher strings. Thought was bad strings. Restrung with new strings. Same issue. My luthier thought Humidity might have been issue since my place was dryer then his shop. Was not the case. I noticed that my open strings where buzzing as well which never happened. I measured the nut and string distance was the same as before.

How could it play flawless for 4 years then one trip to the shop with new pick up and it played like a $200 bass from a pawn shop. My logic after 4 hours of farting around was the pick up. So I lightly plucked the string with one finger and pushed the pick up down with another finger and no buzz. Plucked string with pick up back up and buzz. I lowered that pick up to 3 mm from bottom of string and my bass is back to normal. No fret buzz what so ever. The pick up was pulling the string down when it was in motion.

In my 35 years of playing and setting up my own instruments have I ever came across this. Lesson learned. I called EMG and they had no answers. Said there magnets are low power. Well if you take an fallen key and hold it above the string it will pull your hand down with the Allen key.

So it does happen. I never would have believed it but it happened to me.
 
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#32
Ya. After reading this forum found other people saying same thing. I have always used the pick-ups as a guide for my hand as well. That is why I have a ramp. Helps limit my attack so I can have lower action. Lucky I can still keep the bridge pick up around the same height as before. Lowered it .5 mm to balance volume better with the new neck pick up. Now I have the ramp in-between the pick-ups so I set it the same height as bridge. Not too bad. I don't need to pick that close to the neck anymore now with the new pick up. Position is about 2 inch's from fret board so gets really good warm low end.

I am sure if I had heavy tension strings and higher action never would be a problem. The Dunlop strings I use are lower tension which may contribute to it as well. Love these strings though. Lol. Not gonna change. Thanks for your reply.
 
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