Split coil buzz

[Dazed]

I’m not a particularly strong on wiring or electrics but can just about use a soldering iron.
I have an old non fender bass with a precision split coil. It has a mild buzz/hum. I’ve resoldered the joints and replaced a couple of wires. Put a new bridge wire in but am still getting a dull hum. It’s a standard volume tone passive set up. 
 

If I touch one of the ground points - bridge or the points where the ground connects it drops to almost silent. 
 

If I touch this pin ( or the others along it path) it goes quieter. 

 

Any ideas?

 

Thanks

Edited October 11, 2023 by Dazed

[Baloney Balderdash]

Does the buzz get much worse when touching any of the pole pieces of the split coil pickup (check both sides)?

 

Edited October 11, 2023 by Baloney Balderdash

[Dazed]

Not sure. I’ll check that. 
 

All the coils are live, tapping with something metallic. 

[rmorris]

The fact that the noise disappears when you touch the grounded metal parts - bridge etc - shows that it's properly connected in that sense so that's good.

What's left is screening. Is the screening shown well connected to ground (often this is via pot bodies but these can get loose,

And is the rest of the control cavity screened ? and the pickup cavity  - maybe a screening plate / foil underneath the pickup ?

Also a different pickup might be less susceptible to noise.

[Baloney Balderdash]

20 hours ago, Dazed said:

Not sure. I’ll check that. 
 

All the coils are live, tapping with something metallic. 

I meant with your fingers, does it buzz even worse when you touch any of the pole pieces with your fingers?

[Hellzero]

3 hours ago, rmorris said:

The fact that the noise disappears when you touch the grounded metal parts - bridge etc - shows that it's properly connected in that sense so that's good.

What's left is screening. Is the screening shown well connected to ground (often this is via pot bodies but these can get loose,

And is the rest of the control cavity screened ? and the pickup cavity  - maybe a screening plate / foil underneath the pickup ?

Also a different pickup might be less susceptible to noise.

This ∆∆∆ is how to solve your issue, which is typical from Fender instruments that are all really poorly shielded.

 

In fact, when you touch the metal parts you ground yourself and when you're not grounded, you act like a huge emitting, receiving and transmitting antenna (that has to be grounded to stop the hissing and electrostatic noise).

 

So when fully shielding all the cavities and (star) connecting them to the ground, the interferences emitted and/or transmitted by yourself and all the surrounding electrostatic noises received (and sometimes transmitted) by the pickup(s) will be grounded and make your signal to noise better, almost silent.

[Dazed]

As i mentioned in the original post (or possibly forgot to) it isn’t a fender, but the problem could well be the same.
The thing is it didn’t have the hum originally or I didn’t notice it. Only after removing the pickguard/pickup etc. It isn’t fully shielded. Just a patch under the pots and Jack. Probably original, so around 50 years old. Cavities definitely not. 

It’s mostly an original early 70s instrument so I’d like to where possible keep it original and not replace the pickup but I may put another pickup in temporarily just to see if it’s the pickup causing the noise but I have a feeling it’s something else, a pot or some of the wiring I haven’t replaced. 

[Dazed]

To add, I don’t generally have problems

with interference or electrical noise where I’ve been trying this bass, I don’t have noise problems with other basses in the same environment- cable - amp etc. 

[sandy_r]

On 11/10/2023 at 17:48, Dazed said:

...

It has a mild buzz/hum. I’ve resoldered the joints and replaced a couple of wires. Put a new bridge wire in but am still getting a dull hum. It’s a standard volume tone passive set up. 

If I touch one of the ground points - bridge or the points where the ground connects it drops to almost silent. 

If I touch this pin ( or the others along it path) it goes quieter. 

 

Any ideas?

...

Improving the shielding of the cavities is always a good idea - completely enclosed volumes (ie. including covers/pickguards, etc) covered with either foil or conductive paint, which is then itself given a good ground connection (preferably all sourced from the jack shield lug)

 

In the meantime, you've noticed a change in hum level - have there been any additions/changes in pedal path or amp/settings which might coincide?

 

Edited October 13, 2023 by sandy_r

[Dazed]

No nothing has been changed or added. It’s bass straight to amp. 

[sandy_r]

41 minutes ago, Dazed said:

No nothing has been changed or added. It’s bass straight to amp. 

 

Ok - you've checked the wiring - and no new gizmos ...time to check for sufficient and continuous shielding inside the control/pickup cavities and under their covers, incl. cover shielding making good elect connection with cavity shielding (using a meter/continuity tester, if available)

 

...you might want to pay particular attention to the area surrounding that section of the split coil which has no direct connection to ground (whereas the other section has one wire grounded)

Edited October 13, 2023 by sandy_r

[Hellzero]

That said @Dazed, a short video with the noise itself and the way you suppress it by touching (but with what?) the ground might help.

 

It might also be oxidation of the output jack where the inner metal part is supposed to touch the lead ground...

[rmorris]

4 hours ago, Hellzero said:

That said @Dazed, a short video with the noise itself and the way you suppress it by touching (but with what?) the ground might help.

 

It might also be oxidation of the output jack where the inner metal part is supposed to touch the lead ground...

 

It seems the noise goes away when the OP touches grounded parts so the Ground connection seems fine.

It is proper screening that seems critical here. And keeping in mind that a P type pickup is always susceptible to noise to some degree. And even with good screening a passive bass has little immunity to H field noise (eg from a mains transformer).

[Dazed]

I’ll get a video up of it later today hopefully. 
 

Currently there is no shielding in the cavities and a minimal amount of very old foil on part of the pickguard where the pots and jack are.
There is no  apparent corrosion of the output jack and I don’t get any crackle moving the cable in the jack. 

Edited October 14, 2023 by Dazed

[Dazed]

Here’s the video. Hope it helps.

The whooshing noise you can hear is traffic outside!

 

 

 

[sandy_r]

thanks for doing the video - unfortunately the wiring is completely unscreened once the pickguard is removed from the bass, so it's not representative of its operational conditions.  If the hum level is similar between your video and having the controls and covers all back in place, then it suggests that the cavities and covers all need to be fully lined - and good electrical conductivity provided between each of them, and then one from them to the jack screen lug, too

 

hth

 

[Dazed]

Thanks for the reply. I may be missing something here but I’m not sure what difference the pickguard being in place would be?
The bridge Earth is still in place and nothing else on the body is earthed or screened. 

Edited October 14, 2023 by Dazed

[Hellzero]

37 minutes ago, Dazed said:

Thanks for the reply. I may missing something here but I’m not sure what difference the pickguard being in place would be?

Here, none, but as we all said 8f you want to solve your humming problem, shield all the cavities and star ground them as there is almost none znd it's not a question of pickup.

 

Another possibility is to buy (and use) an Aero dBuz jack-jack cable as it will ground you for the reasons I explained above: https://d-buz.com/

 

Read all the explanations to clearly understand that this will solve your problem and keep your bass untouched as it's a (non Fender with the same issues) vintage bass.

 

Bass Direct is selling these Aero dBuz cables and they are worth every penny: https://www.bassdirect.co.uk/product/aero-dbuz/

 

[Dazed]

Thanks for that Hellzero. I’m just trying to find the cause of the problem, seems a fairly simple set up. As I stated somewhere earlier in this post, the noise started after removing the pickguard and refitting it. I’m sure an expensive cable may resolve it but can’t imagine that is the only solution.
It also didn’t have the noise without the whole cavity being shielded before, so it should be possible to get back to that state. 

[sandy_r]

9 hours ago, Dazed said:

... I’m not sure what difference the pickguard being in place would be?
The bridge Earth is still in place and nothing else on the body is earthed or screened. 

 

Electromagnetic Interference (ie. mains hum, signal breakthrough from your phone, taxi radios outside, etc, etc) can get into your audio in 2 ways: transmitted as radio-type waves across distances, and induced across much closer gaps by a kind of 'transformer' action, wire-to-wire

 

There are 2 well-established ways to reduce this interference problem:-

 

  a) completely enclose the audio circuit in a conductive box (or 'shield');

  b) live in a desert;

 

So - assuming you didn't go for b), take a good long look at your guitar electrics - both when they're out for the video, and when they're back in place, and ask yourself: 'where are the conductive surfaces which effectively make a continuous, albeit 'snakelike', box around every part of wiring?' (from the pickups to the Jack).  Then fill the missing areas with something conductive - and electrically interconnected - until you've achieved a complete encasing of your wiring - which itself is connected to your Jack shield lug

 

Dare I say it: Maybe spend a little time on Y*ut*be, watching instructional videos on techniques?

 

hth

 

[Hellzero]

@Dazed :

 

The cause of the problem is electromagnetic interference.

 

The reason of the problem is lack of shielding.

 

The explanation of the problem is unreliable memory.

 

Don't worry, memory is the least reliable part of our brain and it's a more than well known fact.

 

Shield your bass or buy that cable and everything will be solved.

[Dazed]

2 hours ago, Hellzero said:

@Dazed :

 

The cause of the problem is electromagnetic interference.

 

The reason of the problem is lack of shielding.

 

The explanation of the problem is unreliable memory.

 

Don't worry, memory is the least reliable part of our brain and it's a more than well known fact.

 

Shield your bass or buy that cable and everything will be solved.

I’m sorry, so I understand your reply clearly, are you trying to say I don’t remember if the problem existed or not a few days ago? 

 

When I wrote “find the cause” I was referring to why the problem

started when it didn’t exist a week ago. 
It wasn’t fully shielded then either. 

[Hellzero]

I give up.

[Hellzero]

On 13/10/2023 at 16:25, Dazed said:

The thing is it didn’t have the hum originally or I didn’t notice it.

 

4 hours ago, Dazed said:

When I wrote “find the cause” I was referring to why the problem

started when it didn’t exist a week ago. 

 

[Dazed]

Yes as it says, it didn’t have it originally or was not noticeable. Not I don’t remember.
 

It is noticeable now, since removing the pickguard and when the pickguard was refitted, which is why I posted here for advice, not a disagreement or a diagnosis about my memory. 
 

I’m not sure what your point is Hellzero or what you think you’re winning or who you are helping? 
 

3 hours ago, Hellzero said:

I give up.

 

It would seem not.