Help diagnosing noise

[Thumper02]

Hey TB'ers,

I just swapped out pickups in my Sandberg VS4 p-bass from the default to a Nordstrand blade. Had it done in a good shop nearby, but having a lot of noise after the install. Went back to them, and they said it's just because the pickup is hotter, but would love y'all's opinion. The noise gets much louder when the treble is turned up in active mode, or the tone in passive. Additionally, if I touch the blade of the EA split, it gets much louder. I took a video so you could see what I'm talking about. Any ideas what could be causing this?



Thanks,
Matt

 

[Thumper02]

 

[dwizum]

Looks like Nordstrand power blades. They have copper tape on the bottom of each pickup which contacts the blade. The copper tape has a wire soldered to it. That wire needs to be grounded. If it isn't, you'll get noise like that when touching the blade.

 

[Thumper02]

I’ll check the grounding and see if I can trace it. Thanks dwizum

 

[Matt Liebenau]

This isn’t their P pickup, obviously, but I happen to have this Nordy on the bench. See how the grey wire is connected to the copper tape? That should be connected to ground.

 

[Thumper02]

Here is a pic of the control cavity. Can y’all see anything wrong?

 

[Thumper02]

The grey wire is on the volume pot

 

[Thumper02]

I’ll solder the grey to the ground today, thanks for yalls help!

 

[dwizum]

Another comment - if that one lone strip of copper tape across your control cavity is the only shielding in the bass, that will play a big role in how noisy it is. You might want to consider a thorough shielding job as a next step if it's still noisy.

 

[Matt Liebenau]

The grey and the black are connected at that solder point. I don’t know enough about that preamp to say if that point goes to ground or not though.

 

[Thumper02]

I moved the grey wire over to the ground, but no effect on the noise. Checked the pickup split and the grey is soldered to the copper tape underneath. Check the ground to the bridge next?

 

[Thumper02]

The grey and the black are connected at that solder point. I don’t know enough about that preamp to say if that point goes to ground or not though.

The preamp does look to be grounded

 

[Thumper02]

Here's the diagram, looks like it's correct, except the three ground wires from the pickup are going directly to ground instead of the preamp now. The jack and the volume pot are also not directly connected with a ground wire, rather, they both go to the ground.

 

[mrperkolator]

Looks like Nordstrand power blades. They have copper tape on the bottom of each pickup which contacts the blade. The copper tape has a wire soldered to it. That wire needs to be grounded. If it isn't, you'll get noise like that when touching the blade.

@Thumper02 I believe I saw a video where Cary from Nordstrand helped someone (by advise) to do this. I cant remember where down the YouTube bunny trail of bass I found it. However I'm sure Nordstrand customer service can help, especially if it's Carey.

 

[dwizum]

In terms of grounding the pickups, best practice would be to have the black wires go to the "pickup ground" terminal on the preamp, and the gray wires go directly to the ground terminal on the jack or any other common ground point, i.e. anywhere that's grounded but not the "pickup ground" terminal on the preamp PCB. This separates the signal ground from the shielding ground. In some preamps there won't be a difference at all, but in other preamps this can make a big difference in how much noise gets through.

 

[micguy]

The way to diagnose this is to take an ohmmeter and measure the resistances from the pole pieces and the strings to ground at the output jack. When you have the grounding correct, the resistances will be very low, and you'll have fixed your buzz issue. This is not a difficult thing to fix - it's pretty simple.

 

[Matt Liebenau]

It seems like I’ve read what @dwizum said somewhere. Separate the two grounds and put the black back on the preamp solder tag and the grey on chassis ground, so to speak. Also, yes if you have an multimeter there should be at most 5-10 ohms from the copper tape on the pickup to the sleeve terminal on the output jack.

 

[Thumper02]

Well, I screwed it all up. Just static now, pickups aren’t working anymore. I’m going to take it to another shop. Getting frustrated with myself and worried I’m going to ruin something.