Active PJ Bass treble control noise problem

[pablogilberto]

Hello!

I have an active Fender PJ Bass MIJ.

Controls are:
- Blend Balance for switching/blending Pbass (Neck) and Jazz (Bridge) pickup
- Master Volume
- Bass
- Treble

I noticed that when the Treble Knob is in mid position (center detent), there is noise.
The noise becomes louder at full position (max).
The noise is gone at lowest position (min).

The noise is reduced everytime I hold on the strings and metals parts. A good indication that the grounding is correct.
But it doesn't totally go away when I'm in mid up to full position.
I need to put it to the lowest position to eliminate the noise. But is removes my high-end a lot.
Is this normal?

Also, I'm thinking that when the Blend/Balance is in mid position (center detent) which means PBass (neck) and Jazz (brige) pickup are both selected, it should act as hum-cancelling, therefore, all the noise should be totally gone.
Stilll, the noise doesn't totally go away when both pickups are engaged.


Is this just normal?
Or is it a pots problem? (Bad pots)
Or maybe on the on-board preamp itself?

Thanks!

[thetragichero]

p pickup is two coils wired in series, so full p should be hum cancelling - can you confirm this?
anything with j pickup in it will have some measure of hum, but hum should be 60 or 120hz so not the high frequency stuff
high frequency cause can be lessened with proper shielding and grounding, but my p with bridge humbucker and sheilded cavity still picks up high frequency noise from my computer monitor. of course the treble control will effect this

using a hum cancelling j pickup may also help (I've got a pair of dimarzio area j waiting to go into a 5 string build)

both my basses are master volume/blend/treble/bass. I've found this the easiest control layout
what preamp you using?

[reTrEaD]

Jan 26, 2020 9:40:23 GMT -5 thetragichero said:

but hum should be 60 or 120hz so not the high frequency stuff

Fluorescent bulbs and lamp-dimmers that use pulse-width modulation create harmonics on the 120Hz noise, so that can definitely be heard as higher frequencies.

And although we're conditioned to think of 60Hz (and 120Hz) in the US, Canuckistan, and throughout North America, most other countries have mains frequency of 50Hz.

But I think you're spot-on regarding the P pickup.  If used alone, that should be hum-canceling.  When mixed with the J pickup, not-so-much.

[pablogilberto]

Thanks for the input.

Yeah, I just realized that the Pbass pickup should be hum-cancelling.
The two magnets are indeed opposite.

Still, I get noise (high freq) even when using only the PBass pickup.

The only way reduce it is when I touch the strings.

I guess, this is a shielding issue.

What you think?

[thetragichero]

shielding and/or grounding. the noise stops because you become a path to ground

[newey]

PB said:

The only way reduce it is when I touch the strings.

I guess, this is a shielding issue.

Tragic said:

shielding and/or grounding. the noise stops because you become a path to ground

I said the same a few years back, and promptly got schooled by ashcatlt. As he explained it, your body is a significant source of electrical noise. If the noise disappears when you touch the strings, it is an indication that the string/bridge ground is doing its job properly. It is not that you become the ground, rather, the string ground is grounding the noise coming from your body, grounding it through the output jack to the cable and amp, and from there to the mains.

If the "you become the ground" thing were true, then there should be no reduction in noise if you were wearing rubber-soled shoes and not touching anything metal, etc.

Also, I'm thinking that when the Blend/Balance is in mid position (center detent) which means PBass (neck) and Jazz (brige) pickup are both selected, it should act as hum-cancelling, therefore, all the noise should be totally gone.
Still, the noise doesn't totally go away when both pickups are engaged.

Hum-cancellation is never perfect, even when one has identical coils in a HB that sit right next to each other. Here, you have two highly-dissimilar pickups set apart by some distance. Hum reduction will be even less perfect.

If the amount of hum changes as you roll off the treble pot (but not with the other pots), I suspect the pot. If the amount of noise is enough to annoy you, then it probably isn't normal operation. If you have only the P-Bass pickup engaged, any noise should be minimal, since it is effectively a HB.