JMJ Mustang Bass - 60 Cycle Hum

[Bass Canuck]

I am getting a 60 cycle hum out of my JMJ Mustang bass. With bass volume on full and the gain at 11:00 on my Aguilar TH350, I can increase the master to only 9:00 before the 60 cycle hum drives me nuts. Aren't these Seymour Duncan pickups suppose to be hum cancelling? Is anyone else having this problem? I'm using the proper filters on my power supply, so it is coming from the bass.

 

[mfbolton]

More likely to be a grounding issue than a pickup issue. Does the hum go away when you touch the strings or bridge?

 

[Bass Canuck]

More likely to be a grounding issue than a pickup issue. Does the hum go away when you touch the strings or bridge?

Yes, it does go away when I touch the strings or even the amp. Any solutions?

 

[mfbolton]

Most likely an issue with the grounding wire that goes from the bridge to the electronics cavity. If you aren’t familiar with that kind of work (soldering, etc), I suggest finding a good local tech to repair it.

 

[Axstar]

Most likely an issue with the grounding wire that goes from the bridge to the electronics cavity. If you aren’t familiar with that kind of work (soldering, etc), I suggest finding a good local tech to repair it.

It sounds like the ground wire is intact, as the hum diminishes when he touches the strings.

The issue is that the JMJ Mustangs aren't shielded. OP can ditch the hum by fully shielding the bass.

 

[Bikeguy57]

It's a ground problem. When you touch the strings, YOU become the ground. Check under the hood. Additional shielding is generally not required on these basses.

 

[Turnaround]

It's a ground problem. When you touch the strings, YOU become the ground. Check under the hood. Additional shielding is generally not required on these basses.

NO this is exactly wrong. So long as the bridge grounding is sound, you ground yourself to the guitar when you touch the strings. And when you touch the amp you are doing the same thing. You are grounding yourself to the amp - the amp and guitar grounds are connected together when you plug in. You are the source of noise, and that noise gets drained to ground when you touch the strings, jack, bridge or amp.

 

[Bikeguy57]

NO this is exactly wrong. So long as the bridge grounding is sound, you ground yourself to the guitar when you touch the strings. And when you touch the amp you are doing the same thing. You are grounding yourself to the amp - the amp and guitar grounds are connected together when you plug in. You are the source of noise, and that noise gets drained to ground when you touch the strings, jack, bridge or amp.

Well, I'm not an Instrument Technician, But when I've had this problem, it's been a grounding issue. Maybe you have some constructive advice for the OP?

 

[Turnaround]

The problem is that the system is pickup up noise from you until you touch the strings or otherwise ground yourself. So the solution is to prevent the noise from reaching the circuitry, and that means shielding. Line all the cavities with shielding paint or foil and connect the shield to ground. Make sure that all the shielding is connected together. And make sure there is shielding on the underside of the pickguard where it covers the cavities, and make sure it also touches the shielding in the cavities.

 

[Axstar]

Well, I'm not an Instrument Technician...

You should have left it at that.

As I already pointed out:

It sounds like the ground wire is intact, as the hum diminishes when he touches the strings.

The issue is that the JMJ Mustangs aren't shielded. OP can ditch the hum by fully shielding the bass.

 

[ole Jason]

As stated the JMJ Mustang isn't shielded from the factory so this is normal

 

[KenB]

My JMJ has very little hum or noise unless I'm standing fairly close to my amp head. It's not bothersome when I'm a few feet from the amp.

A few questions for troubleshooting:

1) Have you tried plugging in a different (passive) bass, like a P-bass?

2) Have you tried your JMJ with a different amp?

3) Have you tried a different instrument cable?

4) What happens if you aren't touching the strings and move the bass around the room? Does the hum change as you get closer to the amp, or change the orientation of the bass from parallel to the amp to perpendicular?

5) Just for the heck of it, what happens if you switch the ground lift on your Aguilar?

6) Have you checked that your AC outlet is correctly wired? Try a different outlet in another room. Also try a different AC cord. You never know...

 

[78Stingray]

Have the same bass. Had the same buzzing. Shielded the cavity with copper tape. Buzz went away.
I followed this tutorial.
The Buzz Killer: How To Shield Your Bass

 

[Bass Canuck]

Thank you everybody for your input, it has been helpful. I have called Fender support, the store I bought it from and two well known local master luthiers. At the end of the day, the decision was to return the bass and have it checked out. I returned it and replaced it with a Fender American Performer Mustang Bass, which has absolutely no faults what so ever. I am totally happy with this new bass.

 

[mikecd1]

Just a follow-up on the ground situation. I purchased a JMJ and had exactly the same problem. Following the same wiring as my pbass I painted conductive shielding paint in the cavity (can't believe it didn't have it) and added a wire from the volume pot grounded to the pickup cavity and problem is solved. I also moved the bridge ground and connected directly to the ground on the input jack as that is exactly how my pbass is wired. Should add that I upgraded from the Jin Sung pots to CTS and added a period correct.1 tone cap. Love the sound, love the bass!