Get rid of hum/buzz?

[Bob Jones 5443]

My little Galien-Kruger Backline 112 served me well for a while (the older heavier model before they lightened it up). It has all the volume I'll ever need (practicing and playing with a few friends). Lately there is a lot of hum and buzz noise I can't get rid of. Can that be fixed?

With pandemic restrictions it's hard to bring it in somewhere. I'm in the Bay Area. Ideally, I'd like to have someone knowledgeable look at the entire chain: bass electronics (Höfner Ignition violin and Ovation Magnum III), cable, amp portion (it's a combo), and speaker. The hum has to start somewhere.

I don't really know how to diagnose the cause. It's frustrating.

 

[agedhorse]

Is there hum with nothing plugged into the amp and the volume controls at normal levels?

 

[Bob Jones 5443]

Is there hum with nothing plugged into the amp and the volume controls at normal levels?

Hi aged horse. Thanks for jumping in. Yes, there is a relatively quiet 60 Hz hum with nothing plugged in and the master gain on half. Raising the bass, mid, or treble knobs doesn't change the sound much at all.

When I plug in the Höfner the sound is the same pitch but gets louder. That's with the amp's bass on high and treble off. As I raise the treble gain the noise becomes both higher pitched and quite a bit louder, so loud I wouldn't want it set there to play. So I've only been playing with bass up all the way and no treble gain on the amp. Even then the noise seems excessive to me.

The noise seems unaffected by the choice of neck, bridge, or both pickups.

 

[agedhorse]

Ok, this indicates that the majority of the noise is being generated by (or picked up by) the bass itself (or possibly the cable... are you sure it's not a speaker cable rather than a shielded instrument cable?)

 

[OddSenses]

Does this happen everywhere you play the amp or just one place? could be the electrical.

 

[agedhorse]

Since the amp itself is relatively quiet, that rules out the electrical system as a conducted noise source IME.

There may be a source of EMF (from the electrical system or other cause) that the bass is picking up though, this would be a radiated noise source.

 

[OddSenses]

Since the amp itself is relatively quiet, that rules out the electrical system as a conducted noise source IME.

There may be a source of EMF (from the electrical system or other cause) that the bass is picking up though, this would be a radiated noise source.

EMF is what I suppose I was referring to. In my basement the bass picks up noise but everywhere else is silent.

 

[BassmanPaul]

You're not just sitting too close to your amplifier are you? Pickups love to collect hum from an amp's power supply!

 

[beans-on-toast]

The Hofner Ignition has staple type pickups. These are humbuckers which are supposed to minimize hum. Try rotating ninety degrees and see if it helps reduce the noise. Keep your hands on the strings.

It isn't as easy to shield the inside of a Hofner hollow bodied instrument as it is a solid body such as a Fender. If your bass doesn't exhibit this problem outside your home, there could be an external source of noise that is overwhelming your signal chain. This could be fluorescent lights, a light dimmer, some type of motors, even bad home wiring or junctions. If this is the case, you have to fix it at the source.

 

[Bob Jones 5443]

Lots to check. I'll report back when I've had a chance to test out all these suggestions. Thanks, all.
Bob

 

[FARBass]

I have a similar problem. My Precision bass and GK Legacy 112 buzz loudly in my practice room with fluorescent lights and dimmers. When I brought the bass and amp to an outdoor outlet (only place without a dimmer) it was all dead quiet. I tried the Ebtech Hum X but it did not work. The buzz goes away when I touch the bridge. Any thoughts would be appreciated.

 

[agedhorse]

I have a similar problem. My Precision bass and GK Legacy 112 buzz loudly in my practice room with fluorescent lights and dimmers. When I brought the bass and amp to an outdoor outlet (only place without a dimmer) it was all dead quiet. I tried the Ebtech Hum X but it did not work. The buzz goes away when I touch the bridge. Any thoughts would be appreciated.

Check to see that your bridge is electrically bonded o the ground/sleeve terminal of your bass jack.

 

[jeff7bass]

You're not just sitting too close to your amplifier are you? Pickups love to collect hum from an amp's power supply!

It's a Hofner too.

 

[jeff7bass]

I have a similar problem. My Precision bass and GK Legacy 112 buzz loudly in my practice room with fluorescent lights and dimmers. When I brought the bass and amp to an outdoor outlet (only place without a dimmer) it was all dead quiet. I tried the Ebtech Hum X but it did not work. The buzz goes away when I touch the bridge. Any thoughts would be appreciated.

My band had to swap out some bulbs in our rehearsal space.

 

[FARBass]

Check to see that your bridge is electrically bonded o the ground/sleeve terminal of your bass jack.

I will check that and report back.

 

[FARBass]

My band had to swap out some bulbs in our rehearsal space.

I will give that a try. Thanks!

 

[FARBass]

I opened up my bass and there is a wire coming from the bridge to a capacitor. There is not a separate wire to the jack.

 

[beans-on-toast]

The wire from the bridge is connected to a pot case (the pot’s date code is the 5th week of 1974 BTW) which indirectly connects to the jack’s ground. It would be good to check that the bridge wire is actually connected to the bridge and that the wire is not internally broken. An ohm meter can be used to check the continuity from the bridge to the jack. It should read zero ohms from the jack’s ground to the bridge if things are correct. An infinite resistance is an open circuit and not what you want.

Use your fingers to check that the jack nut is tight. also see if the pot nuts are tight by gently rotating the back of the pot. They need to be tight against the metal shield to complete the ground circuit.

 

[byacey]

I would install a wire jumper between the pot cases, rather than relying on the aluminum foil for signal ground.

 

[FARBass]

The wire from the bridge is connected to a pot case (the pot’s date code is the 5th week of 1974 BTW) which indirectly connects to the jack’s ground. It would be good to check that the bridge wire is actually connected to the bridge and that the wire is not internally broken. An ohm meter can be used to check the continuity from the bridge to the jack. It should read zero ohms from the jack’s ground to the bridge if things are correct. An infinite resistance is an open circuit and not what you want.

Use your fingers to check that the jack nut is tight. also see if the pot nuts are tight by gently rotating the back of the pot. They need to be tight against the metal shield to complete the ground circuit.

The wire from the bridge is connected to a pot case (the pot’s date code is the 5th week of 1974 BTW) which indirectly connects to the jack’s ground. It would be good to check that the bridge wire is actually connected to the bridge and that the wire is not internally broken. An ohm meter can be used to check the continuity from the bridge to the jack. It should read zero ohms from the jack’s ground to the bridge if things are correct. An infinite resistance is an open circuit and not what you want.

Use your fingers to check that the jack nut is tight. also see if the pot nuts are tight by gently rotating the back of the pot. They need to be tight against the metal shield to complete the ground circuit.