L2000 Pickup buzz

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L2000 Pickup buzz

Postby delta90h » Sun Aug 04, 2013 9:26 am

Recently I noticed strange noise on pickups. The noise is appears when I touching right pole pieces on pickups. There is no noise from left pole pieces on pickups. It can be barely heard when on parallel but the buzz is strong when series switch is engaged and even stronger when active switch is engaged.
It happens when i rest my thumb on pickup pole piece during play.
I took the bass to the technician and he checked ground and electronics on bass and said there is no problem. He said this is how the bass designed to be. And he's solution was to cut surgical glove tip and to put it on the tip of my thumb when I play :lol: or not to use series switch.
Image

Is there any solution?
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Re: L2000 Pickup buzz

Postby Ken Baker » Sun Aug 04, 2013 6:13 pm

delta90h wrote:Recently I noticed strange noise on pickups. The noise is appears when I touching right pole pieces on pickups. There is no noise from left pole pieces on pickups. It can be barely heard when on parallel but the buzz is strong when series switch is engaged and even stronger when active switch is engaged.
It happens when i rest my thumb on pickup pole piece during play.


Please refresh my memory: Is this a USA bass or a Tribute?

Some questions for you. Quite a few, but they will help to find the problem.

Has the bass always done this or is it a new problem?

If new, what could have happened that is time coincidental?

Has anyone, you or a technician, made ANY modifications to the electronics? If modifications have been made and were not done correctly, they could cause noise.

Is the buzzing high or low frequency? Low frequency would be mains line frequency - 50 or 60 Hz. High frequency would be pretty much anything else.

Have you tried other cables?

Have you tried other amps?

Have you tried your amp in another location (plugged into different circuit)?

Do you absolutely KNOW that the earth grounding for your amp is working correctly?

When you play do you carry any other electronic devices?

If so, are they battery powered or mains powered?

I took the bass to the technician and he checked ground and electronics on bass and said there is no problem. He said this is how the bass designed to be. And he's solution was to cut surgical glove tip and to put it on the tip of my thumb when I play :lol: or not to use series switch.


This is NOT how the bass is designed to be. My recommendation is to find another technician.

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Re: L2000 Pickup buzz

Postby delta90h » Sun Aug 04, 2013 10:51 pm

Thank you Ken for you replay. It is USA L2000
The noise is high i think.
I think you right about the earth grounding for my amp. My amp have an european plug + - but there is a ground screw on the back of the amp. I put the ground wire to it and it solves the problem. But on the very loud volume I can hear a very little of this noise when on series.
But what to do now? I can solve this problem at my place, but we rehearse at my friends place, bass running in to computer audio interface directly and it surely have grounding problems. Is there any solution beside to carry ground wire everywhere I go ? May be some kind of ac adapter that ad ground to european ac plug?
Nobody made any modification to electronics. One thing were done it is pickup height setup. The technician lowered the pickups significantly.
Image

Can the big distance from pickups to strings boost the noise ? Because before this manipulation I didn't heard this noise even with my poor earth grounding.
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Re: L2000 Pickup buzz

Postby Ken Baker » Mon Aug 05, 2013 8:49 am

delta90h wrote:Thank you Ken for you replay. It is USA L2000
The noise is high i think.
I think you right about the earth grounding for my amp. My amp have an european plug + - but there is a ground screw on the back of the amp. I put the ground wire to it and it solves the problem. But on the very loud volume I can hear a very little of this noise when on series.


This is consistent with environmental electrical noise. It could be lighting in your space, it could be certain types of motors, it could be electronic equipment. It could even be a noise source in the local power grid. Grounding of the amp usually cures the noise, and more importantly make it safer to use.

But what to do now? I can solve this problem at my place, but we rehearse at my friends place, bass running in to computer audio interface directly and it surely have grounding problems. Is there any solution beside to carry ground wire everywhere I go ? May be some kind of ac adapter that ad ground to european ac plug?


Contact a local electrician.

Can the big distance from pickups to strings boost the noise ? Because before this manipulation I didn't heard this noise even with my poor earth grounding.


The strings are connected to the chassis ground of the bass/amp. This is separate from earth ground in a lot of cases. Pickups, even humbuckers, can act like little radio antennas and pick up ambient environmental electrical noise. When the strings are close to the pickups they may be acting like shielding - a Faraday cage - that effectively stops the noise from getting to the pickup.

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Re: L2000 Pickup buzz

Postby delta90h » Mon Aug 05, 2013 8:59 am

OK. Thank you.
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Re: L2000 Pickup buzz

Postby delta90h » Wed Aug 21, 2013 2:41 am

Soo I continuing to struggle with noise in places with poor ground.
So i looking for portable solution for this to carry around for such places.
Someone recommends me to use DI box.
Can someone confirm that it is may be the solution?
If yes. What will be your recommendation for DI boxes? Maybe some combined DI preamp pedals?
And if yes will I must use DI XLR output to audio interface/mixer/combo to cancel the noise or it will also affect PL to PL connection from DI box to audio interface/mixer/combo
Because not all devices equipped with XLR inputs.
I am not using long cable 3-5 m. But sometimes I connect my bass direct to audio interface/mixer.
Even when I connect bass to combo without ground there is a noise.
So will DI box cancel noise?
Noise gate is less preferable and more expensive solution for me because to much intervention in sound.
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Re: L2000 Pickup buzz

Postby GeorgeB » Wed Aug 21, 2013 2:30 pm

The problem is a (minor) design flaw of the MFD pickups, the pole pieces are not connected to ground.
In parallel mode both coils of a pickup have one end connected to ground so the winding actually shields itself from the injected noise when touching the pole pieces.
In series mode one coil is connected on top of the other so that coil cannot shield itself anymore.
Gounding the poles would solve it completely but it is not very easy to do.

A good passive DI box with an isolation transformer would most probably help quite a bit, while so-called active DI boxes would not. Drawback of passive DI box is that it will load down the pickup with the bass running in passive mode, causing a loss of higher frequencies. In active mode it would work well, though.

Another option would be to isolate the pole pieces in question by placing a small piece of plastic sheet etc on it so there is no electrical contact from your skin to the pole when touching it. Same concept as with wearing gloves.
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Re: L2000 Pickup buzz

Postby Ken Baker » Wed Aug 21, 2013 6:25 pm

GeorgeB wrote:The problem is a (minor) design flaw of the MFD pickups, the pole pieces are not connected to ground.
In parallel mode both coils of a pickup have one end connected to ground so the winding actually shields itself from the injected noise when touching the pole pieces.
In series mode one coil is connected on top of the other so that coil cannot shield itself anymore.
Gounding the poles would solve it completely but it is not very easy to do.


While grounding the pole pieces might help, I think it would be better to attack the problem closer to the source. In other words, either fix the earth ground in the building or find a way to connect a proper earth ground to a ground lug in/on the amplifier. This will cure the problem and add a good amount of safety to the amp's circuit.

A case in point, kind-sorta:

I started having a helluva problem with 60Hz buzzing noise (not hum) while playing in my office here at home. My L-2500 (fully shielded) was incredibly noisy in ANY mode, and it didn't matter whether or not I was touching anything. Using a single coil pickup was out of the question. I was able to trace the noise to a large brass table lamp on my desk. It wasn't leaking current to ground that I could detect, but it sure was acting like a great antenna transmitting the noise. So I replaced its 2 conductor power cord with a 3 conductor cord, connecting the ground lead to the brass of the lamp. Problem solved - completely. My office isn't exactly a haven from EMI, with 2 or 3 computers, CFL lighting, and commercial grade networking equipment. But the bass is now as it should be - noise free.

Moral of the story here is to attack this sort of ground problem as close to the source as possible.

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Re: L2000 Pickup buzz

Postby bdgotoh » Wed Aug 21, 2013 7:57 pm

Very interesting story Ken. How did you figure out it was the brass lamp? Where you able to get more noise as you put the bass closer to it?
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Re: L2000 Pickup buzz

Postby Ken Baker » Wed Aug 21, 2013 8:49 pm

Being an IT guy, I carry signal trace tools in my bag; the same ones phone guys use:

Image

This is the receiving end of the kit, a tone probe. The other end is a small tone injector, which I didn't use here. Think of the probe as a single coil pickup with a little amp & speaker attached. I walked around the house and my office using it to look for offenders. It turns out the house is actually pretty quiet - except my office. Walk through the door and the thing got notably loud. It was easy to trace to the lamp. Once I fixed the lamp all the other stuff in the office could be heard, but not too loud and easily within the capabilities of a humbucker to reject.

The lamp is a pretty old 3-way that is in good condition. I had changed the incandescent bulb out for a 3-way CFL, and I'm wondering if that may have set up a resonance of some sort between the inside wires and the brass. I dunno - I didn't think to swap in an incandescent to try. CFLs on their own are actually really quiet. I had to get right on top of them to hear any EMI and it was a high pitched whirring sound. LCD display panels are quiet too, as are the computers. The HP gigabit switch, OTOH, could be heard.

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