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Keep buying basses - my learnings (Shielding content)


Ander87
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Hi all,

 

Thought I'd share a good story. I recently bought a P bass without a pickup as I had a couple of spares. I installed the first pickup (BKP '58 P) and noticed noise unless I'd touch the strings. I went in again after being unable to sleep (it be like that sometimes I guess!) to change for another pickup (Herrick split '58 P) in case it was a pickup issue... And funked up the electronics further; since my soldering was poor, I somehow made the volume pot work from closed to fully opened in half the run of the knob - further than that there'd be no sound whatsoever. Some would optimistically say I upgraded the knob to a kill switch almost, but let's face it, it was a mess.

 

I got a quote for my technician for adjusting repair swapping pickup and electronics and with the help of this forum diagnosed that if the noise disappears when touching the strings, it may be a shielding issue, especially considering this bass had none whatsoever.

 

Ordered copper shielding tape just to entertain the idea of doing it myself for £5 - it arrived this afternoon and with the whole evening ahead I decided to try myself.

 

I AM IN NO WAY AN EXPERT BUT THOUGHT I'D SHARE WHAT WORKED FOR ME!

 

I removed all parts of the bass including the bridge to review the grounding/earth connection (a first as well):

 

image.thumb.png.73d8f6ffd7f1fb3cdb06e49c62bff98c.png

 

Stripped the whole thing down: 

 

image.thumb.png.e89224c33694658a7eaeb5c42e4d7e4e.png

 

Started easy with the reverse of the pick guard - the point is making a Faraday cage, so it needs to be a copper tape covered enclosure:

 

image.thumb.png.0b7f18b8682ad3ccdf7bf1ecd6dfe164.png

 

My first tip: use the tape on top to rub on the edges of the pick guard so that you know where to cut, take half a millimetre or abouts in so that the tape won't show over the pick guard from underneath once installed.

 

Second tip - don't underestimate an actual pen/knife cutter! I did it all with scissors and whilst it worked okay, it would've been easier for the holes specially.

 

I was thinking of doing half the thing but the top is easier which is what I left for the end so since I was on it I shielded the whole thing.

 

Moving on to the cavities. Again, I started with the most difficult part, the controls cavities. My take was to cover the walls first, this time allowing a millimetre or two extra so that it would fold over the face of the bass (careful to not offer too much lip folding over as that may show over the pick guard! 1mm or 2max is safe tough.

 

Once you have the walls covered, doing the base of the cavity is easier than I thought. Then once you have the gross covered you'll have to invest more tape in covering the irregular (non square parts) of the cavities.

 

One annoying thing about copper tape is that it curls up the moment you remove the reveal the adhesive part - advise online would say to remove the non-coppery bit instead of the copper but in all honesty I couldn't as the paper is thicker than the copper tape. What I did would be holding both edges of the strip as I remove the paper cover so it wouldn't curl up.

 

image.thumb.png.c6346567ad5b19b0de6de2039a80398d.png

 

Another tip - I was initially neurotic about holes (screw holes, cable holes in the body etc); I was thinking covering them would mess up my chances to reveal those holes in or that I'd have to push them with the cables when installing again - silly, I know. Just get a paper clip or a pair of tweezers and feel through the wood to pierce them. This is much easier than making cutouts and trying to avoid the holes etc, and also ensures 'the cage' is covered all around.

 

I then moved onto the pickup cavity:

 

image.thumb.png.bced3b0a59ecf440fbf9569343ef1a7f.png

 

Job done! I'm aware I could've documented strips here and there but I wasn't initially planning for this post even, sorry!

 

image.thumb.png.cc98e8ce50a414688f04b2d9a66c5d3d.png

 

From then, solder back, screw it all in and throw a quick prayer to Jaco that it works. I spent some extra time cleaning the soldering as the ground soldering was a bit messy on the pots thanks to my previous attempts. Sucking out the extra lead with a tool was really useful and cleared things up. Another note, I should've bought/had a multimeter at hands reach to check for continuity of the layers of copper foil. It all worked but in hindsight I would've preferred that over praying it works, even if it's Jaco we're talking to.

 

As mentioned, I closed all in, plugged in et voila! all working as it should and the noise is nonexistent in clean, and a slight bit present on distortion (but this is distortion at 2 o'clock on a Darkglass microbes anyway with the compressor up, understandable). Also the cleaning of soldering did pay off as the volume pot is back to normal operation!

 

This has been a good learning that sometimes we're too scared to touch things up - the quote I would've gotten in most luthiers would have been £100+: £20 pickup install, £20 review electronics, £40 shielding, £45 general adjustment... £125 altogether! It has been a good 2/3 hours with The Walking Dead in the background and £5 for copper tape - probably not my fastest job but believe me, the beer after tasted glorious.

 

I have been the kind of person that has constantly taken guitars and basses to luthiers/technicians at the earliest chance for adjustments and anything else - bass after bass I've realised that those guys that said 'learn to do it yourself' were right all along! Personally I find that small tweaks on each bass that came through my hand has offered me more insight into how to take care of my gear. To think I was terrorised at the thought of touching a truss rod! I have since done adjustment works for friends and acquaintances and been praised for the results, so I hope this post helps encourage people to take up on it, the satisfaction and the savings are worth it!

 

image.thumb.png.6a063ce1ff7d6d2d32cc9ed215894155.png

 

Best,

 

Ander.

Edited by Ander87
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You know that shot with the earth wire under the bridge ?  Put a stripe of copper tape over the end of the copper wire to hold it in place and then screw the bridge down tight. 
 

also use a stripe of tape to join the pickup cavity and control cavity in case the pick guard ever worked loose 

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2 minutes ago, Geek99 said:

You know that shot with the earth wire under the bridge ?  Put a stripe of copper tape over the end of the copper wire to hold it in place and then screw the bridge down tight. 
 

also use a stripe of tape to join the pickup cavity and control cavity in case the pick guard ever worked loose 


Oh amazing, thank you!! Will give that a go. I did think about the strip on the bridge but wasn’t sure if that’d mess things up!
 

When you say another stripe to connect the cavities, I’m assuming you mean over it?

 

Thanks again those are brilliant ideas!

 

Ander. 

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7 hours ago, Ander87 said:


Oh amazing, thank you!! Will give that a go. I did think about the strip on the bridge but wasn’t sure if that’d mess things up!
 

When you say another stripe to connect the cavities, I’m assuming you mean over it?

 

Thanks again those are brilliant ideas!

 

Ander. 

Yes - stripe over the top to join cavities - do this on jazz basses too

 

The other reason for bridge wire tape is you might tug on it when moving the pick guard 

 

You don’t need to poke holes with a paper clip - just smooth the tape out with your finger and you’ll see the holes 

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12 hours ago, PaulThePlug said:

Over the bit of body, between the cavities... 1/2" - 3/4" wide, so it gets hidden under the pick guard...

 

Thaks, will do!

 

4 hours ago, Geek99 said:

Yes - stripe over the top to join cavities - do this on jazz basses too

 

The other reason for bridge wire tape is you might tug on it when moving the pick guard 

 

You don’t need to poke holes with a paper clip - just smooth the tape out with your finger and you’ll see the holes 

 

Noted - and yes going through it with fingers made sense - as I had never used copper tape I assumed it was harder to work or pierce through.

 

25 minutes ago, rmorris said:

Nice. It would have been easier to check the bridge continuity with a multimeter rather than remove/refit.

Bear in mind that you can't totally eliminate noise pickup as some will 'get in' via the pickups themselves.

 

 

I didnt have to remove/refit but a multimeter would have been easier rather than 'wonder/meter would have been easier rather than 'wonder/hope' it works.

 

I have heard about using clear nail polish for the poles to try and isolate a bit more, thoughts? Having said that the bass is really quiet now, especially by comparison!

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2 minutes ago, Ander87 said:

 

 

 

I have heard about using clear nail polish for the poles to try and isolate a bit more, thoughts? Having said that the bass is really quiet now, especially by comparison!

 

That's a bit different - to stop you making skin contact with exposed pole pieces and causing noise. Depends on playing technique whether it's an issue. Any colour will do the job !

Although real solution is to have pickups with non-exposed pole pieces / rails.

 

I was meaning that the pickups themselves are usually not themselves shielded by design.

 

 

 

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I did a similar thing to a fairly noisy Warwick active bass with Nordstrand pickups. I was slightly surprised that I also had to ground all of the pickup pole pieces to make the bass really noise free. I used a combination of conductive paint (the kind used for car rear screen heater repair) and the self adhesive copper foil to get good continuity across the back of the pickup. This did not affect the tone but the bass was much quieter.

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On 17/09/2021 at 12:53, Ander87 said:

Aha, got it, all clear now @rmorris, thanks!

 

I guess the route to isolate the pickups further would be wax potting etc...

Potting doesn't affect interference noise. Wax has no RFI shielding properties. It can help to minimise microphonic effects where the pickup magnets/coils move in relation to each other.

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11 hours ago, basstone said:

I was slightly surprised that I also had to ground all of the pickup pole pieces to make the bass really noise free.


oh! This is something I want to learn more on! The bass is REALLY quiet now but this could make it zero noise? The gain I use can be quite hissy so maybe that would help yet further although I’m not sure that it can get quieter!

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45 minutes ago, Ander87 said:


oh! This is something I want to learn more on! The bass is REALLY quiet now but this could make it zero noise? The gain I use can be quite hissy so maybe that would help yet further although I’m not sure that it can get quieter!

Try grounding different things with a wire to see if makes an improvement before spending time on screening to track down the dominant source of noise

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On 18/09/2021 at 21:17, Ander87 said:


oh! This is something I want to learn more on! The bass is REALLY quiet now but this could make it zero noise? The gain I use can be quite hissy so maybe that would help yet further although I’m not sure that it can get quieter!

 

If you are referring to a constant highish frequencies hiss (ssss...white/pink noise) then that isn't interference  It's inherent noise bring amplified. The noise  comes from the pickup itself, the preamp/amp and interaction between the two.

Normal passive pickups are High Impedance and regarded as a noisy source in electronic terms. Actual noise level will depend a bit on the preamp/amp it is plugged into.

Try low pass filtering / treble cut to reduce audible noise. How much you can do much depends on your desired tone.

But bear in mind that there's little signal from a bass above a few kHz.

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