Interference in a pickup

[EtherealEntity]

Hi - not sure if this is the right place to post this, but lastnight I was playing guitar direct into my 6505+ which is 5 feet behind me now. I was sitting infront of this laptop, and I could hear weird electronic beeping noises etc. coming from my amp. After a while I realised it was only when my bridge pickup was in use (swtich in middle or far side).

I was thinking it was a loose wire in the pickup or something, but today it isn't doing it. Then I turn my laptop on and it starts again. Still only one pickup.
My other guitar also does it but only on certain pickup positions.

Anything I can do to stop this? Besides not playing infront of my laptop
It's audible about 2-3 feet from the laptop and then goes away.

And why is it only on certain pickups? They are all humbuckers, by the way.
Thanks

 

[Zaphod B]

Shield the pickup cavity.

 

[danw]

Would the shielding still be an issue on a humbucker? I thought that was kind of the point, that interference coming from outside the coils would cancel out.

 

[Zaphod B]

Would the shielding still be an issue on a humbucker? I thought that was kind of the point, that interference coming from outside the coils would cancel out.

Normally it's not, but he's standing right in front of an agressive RF emitter (the laptop).

 

[glasshouse]

less than a buck solution:

take the PU out, remover any plastic foil or insulation around the coil, put hot candle wax on the coil (now, dont overdo it..), cut a piece of aluminium foil wrap it around the coil, tape it together, put the shell back on, and back in the git.

if you have plastic covers for the PU's or the electronics inside, make sure you have aluminium foil on the inside.

 

[Zaphod B]

I'm not convinced that potting the humbuckers will insulate them from a strong nearby RF signal, and it may squelch a little of their liveliness.

Rather than using aluminum foil you can buy self-adhesive copper shielding, or use conductive shielding paint. Either way the shielding has to be grounded.

 

[JCH]

less than a buck solution:

take the PU out, remover any plastic foil or insulation around the coil, put hot candle wax on the coil (now, dont overdo it..), cut a piece of aluminium foil wrap it around the coil, tape it together, put the shell back on, and back in the git.

if you have plastic covers for the PU's or the electronics inside, make sure you have aluminium foil on the inside.

^This is not good advice.

The first thing I'd try is a different guitar cable.

 

[glasshouse]

well, its cheaper than to say to buy a proper equipment....
if you wanna record properly you need the proper equipment and the proper environment around it, its that simple...
and if you dont have the dosh to do that, you have to look into cheaper alternatives. the wax will eliminate most of the humming, copper has no direct advantage over aluminium.. i do agree on the RF issue, but then: where is your RF source? electronic material is shielded due to regulations, there's no difference between a pc and a notebook. the pc has even worse shielding levels than the notebook.

 

[glasshouse]

...and yes, proper guitar cable is a must....

 

[lpdeluxe]

Shape aluminum foil into a cover for your guitar, solder a wire lead to it, and attach the other end of the lead to a ground.

Seriously, don't play in front of the lap top. At least it's not a CRT: I was overdubbing bass in my studio right after I got my computer rig and the track sounded like bacon frying. I learned that turning the bass to right angles to the screen cured the problem.

 

[Zaphod B]

i do agree on the RF issue, but then: where is your RF source? electronic material is shielded due to regulations, there's no difference between a pc and a notebook. the pc has even worse shielding levels than the notebook.

Computers are compliant to, what, FCC Class B but whatever it is, it allows a very high level of local RF emission. Old-style CRT monitors are the worst offenders but any computer is pretty much spewing RF in all directions simultaneously. It's low-power though, so it only has any effect up close.

 

[JCH]

well, its cheaper than to say to buy a proper equipment....

I didn't tell him to buy anything. I suggested that he try another cable.

..if you wanna record properly you need the proper equipment and the proper environment around it, its that simple...

Who said anything about recording? He's hearing the interference through his amp.

and if you dont have the dosh to do that, you have to look into cheaper alternatives. the wax will eliminate most of the humming,

It will not. Potting a pickup will have no effect on RF interference.

copper has no direct advantage over aluminium..

I'll remember that next time I'm soldering aluminum

.. i do agree on the RF issue, but then: where is your RF source? electronic material is shielded due to regulations,

The source is his laptop. He said it only happens when he's within 3 feet of it.

..there's no difference between a pc and a notebook. the pc has even worse shielding levels than the notebook.

My PC lives in a big metal case. My laptop is mostly plastic.

I posted that it was bad advice because it is. What you suggested would significantly compromise the sound of the pickup. Have you ever tried this? What were your results?

In my experience a closed loop like you speak of wrapped around a coil will very noticeably darken the tone. It will also muddy the tone because of eddy currents that are introduced in the magnetic field. What you described could also be very microphonic.

A better method is to shield using an open loop. One that does not go completely around the coil. This is usually only done on single coils. Humbuckers cancel RF by their nature. Thats what they do.

He also said that it only happened with the one pickup. It is possible that pickup has a shorted coil which would make it more noisy than others.

I'd still try a different cable first. The easiest solution would be to sit further from the computer.