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How to Differentiate between Pickup noise and Preamp noise

E

Escher Step

Sep 13, 2022
3
0
#1
I recently bought a 6 string bass with two soap bar style Bartolini pickups, and an active Audere Preamp. The preamp has 4-band eq, blend knob, master volume and a z-mode switch.

When I demoed it it sounded flawless, but I play with a lot of gain and effects so when adding my rig into the equation, the little bit of high-mid freq noise it was producing became more of a noticeable problem (especially for an obsessive perfectionist like myself). I assumed the pickups were humbucking so I beefed up the shielding job and resoldered some questionable spots, but the humming persists.

I can't find any model number on the pickups so I can't say for sure if they are humbucking but those seem to be the most common. If i knew what was inside the pickups I could assume the problem lies within the preamp/wiring somewhere but the pickups are sealed up as Bartolinis are.

Does anyone have any advice for helping me diagnose the issue? I've at least deduced that the issue lies within the bass, not the environment or other equipment.

I have a gig and some sessions coming up next month that I plan to use this bass for so I would love to figure this out as soon as possible.
 
#2
Things you can test:

-If noise volume does not decrease by decreasing the pickup volume, the noise is the preamp. I believe the Audere is active volume control (not before preamp). So, I don't think this test would reveal anything.

-Hard to point fingers without bypassing the preamp.

Realize that no bass will be completely noise free. Good bases have very good signal to noise ratio. The noise is just so small, you don't notice it. Sounds like you bought a good bass with quality components. Adding gain raises the amplitude of the whole signal (notes and noise). Distortion and compression reduce the volume of the notes, but not the noise. So, SNR goes down.

My advice is put a noise gate at the start of your pedal board.
 
#3
From the title of the post, I’m guessing you are trying to determine is the noise is coming from the pickups or the preamp?

If that’s the question, one very coarse way I check that is to move the bass around to see if the noise changes. If it does, then the pickups are picking up extraneous interference in the space. If it’s a steady kind of noise, then it’s probably starting in the preamp.

Based on what I’m reading, I would start with the bass only plugged in to your amp. If that’s quiet or at least acceptably so, start adding your gain and effects, one at a time and see when and where it gets noisy (er). That will help diagnose your issue and decide how to address it.
Good luck.
 
#4
This post seems to be in need of some clarification. I know the noise is rather being picked up by my pickups or my preamp. Definitely not my other gear or my amp. The noise level might be considered acceptable for single coils, but I thought I was buying humbuckers, so it's actually not acceptable at all. Rather these are single coils or defective humbuckers.

So perhaps a better question is how to tell if my pickups are single coil or not when they're soapbar-style like mine are. If they're single coils, I'll be replacing these regardless if the noise is "acceptable" or not.

If they're humbuckers and the noise is coming from them, I will be replacing them.

If they're humbuckers and the noise is not coming from them, that means it's an issue with the wiring or the preamp, and I can then go on to rather fixing or replacing the preamp from there.
 
#7
Magnetic flux viewing film will show you magnet configuration. I bought some on Amazon for around $12.

F2A16075-A2E2-4000-8077-C4E3EB2F8499.jpeg
 
#8
There are pickups that hum cancel just fine that will look like single coils on magnetic film - stacks and sidewinders only have one line of pole pieces (or one bar) and they hum cancel. While that's a useful test (it tells you something), it's not conclusive as to the point of hum cancelling or not.

If you do have single coils, be aware that there are two sources of hum/buzz noise - shielding deals with electrostatic hum, but electromagnetic hum will not be affected by electrostatic shielding (no matter how well you do it) - the only cure for that is a hum cancelling configuration.
 
#9
Escher Step said:
little bit of high-mid freq noise
Click to expand...
If your pickups are not humbucking, you will hear 50/60 Hz hum when balanced to just one pickup.

If you want to know what frequency the noise is at, you can do a FFT on a sound sample. Audacity is free and easy software.

I have heard stories of preamps and particular pedals not getting along well together. You end up with an oscillation circuit. There are many stories of pedal X not working well with pedal Y without isolated power. The preamp in your bass is essentially a pedal. If not already using batteries or an isolated supply for your pedals, try it out.
 

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