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Single coil, 60 hz hum, DIY instrument
#3039708 04/20/20 01:40 PM
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Hi everyone,
for the past months I've been building an instrument which is somewhat similar to a Clavinet. It has single coil pickups wired in series, mounted under and above the strings. Since this is a keyboard instrument and pretty much stationnary, I can't "find the Mecca". Now, I've done a lot of experimenting with shielding (the ground is connected to the ~20 lbs steel frame), and I still have a bit of 60 hz hum. I really love the tone of the single coils and would like to keep them.
I know this topic is beaten to death, but my situation is a bit particular. When I physically remove the pickup from the instrument and move it around, I can easily find the sweet spot by putting the pup in a vertical (like a guitar) position, and that bit of hum pretty much DISAPPEARS. However, as I said, the pup HAS to be in a horizontal position. It looks like no amount of shielding will help.
If you'd like to see what the instrument is, the three last videos on my youtube channel (link in my signature), show it in action.
I might resort to humbuckers or some kind of noiseless single coils, but if I could get rid of that hum, that would be the holy grail of tone to me.
Any suggestion??
thanks in advance,
Martin


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Re: Single coil, 60 hz hum, DIY instrument
bourniplus #3039725 04/20/20 03:58 PM
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All a humbucking coil really needs to do is pick up the hum and reverse the phase of that hum.

Alembic guitars - many of them have a "dummy coil" that has no magnets. It doesn't even need to be under the strings, just nearby.

How many total strings/pickups are there? Maybe you can just run leads at the halfway point and reverse the polarity of half the pickups. Try series and/or parallel connections and see which sound you will prefer and which cancels the hum most effectively. I am pretty sure you will change the tone of the output to some degree but it should still have that single coil tone.

It may work best reversing every other coil, simply that each pair of hum cancelling coils is in closer proximity to that specific source of hum. But each pickup is stil picking up only one string (or mostly so depending on spacing).

Something that may help with the unit as-is - Are you just plugging everything into the wall or using power conditioning/noise filtering? I added a Furman P-8 Pro C to my studio rack and it made a significant difference in eliminating EMI. If I plug my amp into that power source my old Silvertone Danelectro hums considerably less. Of course, I can move around and find the sweet spot with the guitar, that's always best.

Experiement with phase reversal and series/parallel configurations, you'll find something that works! Cheers, Kuru


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Re: Single coil, 60 hz hum, DIY instrument
bourniplus #3039733 04/20/20 04:20 PM
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There are Fender single coil noiseless pickups at Sweetwater. They come in sets of 3 for $135 to $199 a set. Good luck and have fun with the project! cool


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Re: Single coil, 60 hz hum, DIY instrument
KuruPrionz #3039743 04/20/20 05:49 PM
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Originally Posted by KuruPrionz
How many total strings/pickups are there? Maybe you can just run leads at the halfway point and reverse the polarity of half the pickups. Try series and/or parallel connections and see which sound you will prefer and which cancels the hum most effectively.

There are 50 strings, and I need 3 pickups to cover them all. They're soapbar style, and I got them in a set of 10 on ebay. Yes they're cheap, but they sound allright to me and they can also be quiet, just not in horizontal position. In order to connect them in series, I modified them so that the base plates connect to a common ground instead of one lead of the pickup. Some are "bridges" and some are " necks", the bridges and necks have different magnet polarity. I've experimented a lot with different combinations of these, with physical position, phase/out of phase, etc, until I got to the point where I am now.
So, I have two "pickup bars", each made of three individual pups in series (have tried parallel but didn't like the tone as much), and I haven't found a way to make them hum-cancelling. When I want to hear both "pickup bars" together, they get connected in parallel.
It looks like I'd have to remove half of the magnets and switch their position to get the hum-cancelling effect. But even then, I know I'm being picky but I'd still like to use only one "pickup bar" without the noise. I have a feeling it should be possible since they become virtually noiseless when I hold them vertically...
I'm also aware of noise gate pedals but I want to try everything else first. I may try one of these power conditioning units.


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Re: Single coil, 60 hz hum, DIY instrument
bourniplus #3039752 04/20/20 06:14 PM
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Is the power supply mounted inside the cabinet? Does it have to be?

Last edited by hurricane hugo; 04/20/20 06:14 PM.
Re: Single coil, 60 hz hum, DIY instrument
bourniplus #3039760 04/20/20 06:27 PM
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Originally Posted by bourniplus
Originally Posted by KuruPrionz
How many total strings/pickups are there? Maybe you can just run leads at the halfway point and reverse the polarity of half the pickups. Try series and/or parallel connections and see which sound you will prefer and which cancels the hum most effectively.

There are 50 strings, and I need 3 pickups to cover them all. They're soapbar style, and I got them in a set of 10 on ebay. Yes they're cheap, but they sound allright to me and they can also be quiet, just not in horizontal position. In order to connect them in series, I modified them so that the base plates connect to a common ground instead of one lead of the pickup. Some are "bridges" and some are " necks", the bridges and necks have different magnet polarity. I've experimented a lot with different combinations of these, with physical position, phase/out of phase, etc, until I got to the point where I am now.
So, I have two "pickup bars", each made of three individual pups in series (have tried parallel but didn't like the tone as much), and I haven't found a way to make them hum-cancelling. When I want to hear both "pickup bars" together, they get connected in parallel.
It looks like I'd have to remove half of the magnets and switch their position to get the hum-cancelling effect. But even then, I know I'm being picky but I'd still like to use only one "pickup bar" without the noise. I have a feeling it should be possible since they become virtually noiseless when I hold them vertically...
I'm also aware of noise gate pedals but I want to try everything else first. I may try one of these power conditioning units.

So you have 4 pickups lef out of the 10?

Try wiring those out of phase, if it isnt too much work you could just remove the magnets. That makes positioning them easier since they will no longer pick up the strings, just the hum. So you could put them under the strings somewhere if there is space and run them in parallel out of phase - by pass the switch so they are always on. That should cancel at least some of the hum and give you your options regarding which set of pickups you want to use for tones you need.


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Re: Single coil, 60 hz hum, DIY instrument
hurricane hugo #3039799 04/20/20 08:41 PM
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Originally Posted by hurricane hugo
Is the power supply mounted inside the cabinet? Does it have to be?
There is no power supply, it's stricly passive, straight from the pickups to the jack..


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Re: Single coil, 60 hz hum, DIY instrument
bourniplus #3039805 04/20/20 09:11 PM
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If you touch the steel frame (ground), does the hum go away?


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Re: Single coil, 60 hz hum, DIY instrument
KuruPrionz #3039809 04/20/20 09:22 PM
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Originally Posted by KuruPrionz
If you touch the steel frame (ground), does the hum go away?
No, absolutely no difference. I'm familiar with that phenomenon in electric guitars, but in this case it doesn't work. I assume it's because the massive steel frame provides enough shielding by itself...?
I've also tried putting the pickup bar in a grounded metal bucket, closed with a metal lid, thinking no hum could get in there! That bit of 60 hz hum was still there, unless the pickup was placed vertically.


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Re: Single coil, 60 hz hum, DIY instrument
bourniplus #3039844 04/21/20 12:21 AM
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Just eliminating all the variables.

A steel frame in and of itself does not represent ground. I have no idea why touching the bridge on a passive guitar with a ground wire to the bridge makes it quieter either, a human shouldn't represent ground either unless they are somehow connected.

I found out the hard way a couple of times that a human can represent a PATH to ground through the ground wire if the house wiring is not in order and one gets too close to a microphone.
That's a different circuit though.

Other than reversing polarity on some of the pickups (which is how a P-Bass cancels hum), I am out of suggestions. Please let us know what you figure out.


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Re: Single coil, 60 hz hum, DIY instrument
bourniplus #3040054 04/22/20 02:51 AM
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This article may help a little:

https://www.samash.com/spotlight/60-cycle-hum/

Good luck on finding the culprit(s)...and keep us posted. cool


Take care, Larryz
Re: Single coil, 60 hz hum, DIY instrument
bourniplus #3041353 04/30/20 12:55 PM
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Martin, you are a Hammond player I think. By chance does this thing sit on your Hammond? There used to be problems with Clavinets picking up hum from the Hammond transformer. Sometimes would sit a sheet of metal between the Clav and the organ to limit the noise.

Last edited by CEB; 04/30/20 12:59 PM.

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Re: Single coil, 60 hz hum, DIY instrument
CEB #3041741 05/02/20 06:05 PM
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CEB, indeed my house is full of Hammonds, but none is close to this instrument at the moment! smile
Actually I tried putting my laptop on top of the electric clavichord (the instrument in question) and read some sheet music, but the noise is so annoying I couldn't stand it, even with many sheets of metal in between. I had to raise the laptop about one foot high on a cardboard box. Tablets are ok.


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