Bass hums, but only when not on full volume

[chyc]

Hi everyone,

As I progress and learn the nuances of playing bass guitar, after 20 or so years' playing I have come across this knob I believe people call "volume". Now my bass may have had this from day dot, and I'll never know as I've only ever started fiddling with this control, but when I dip the volume down I get an annoying an audible hum. Full volume and zero volume are dead silent.

At this point I would usually take the bass to someone more qualified, but I'm kind of stuck at home with nothing better to do, so I'm asking for help here. Is this a common occurence and is it an easy self fix? I see general hum issues, but not related to when the volume is only partly engaged. The offending bass is a Sandberg California which I've owned from new around 10 years with no mods.

 

Any help gratefully appreciated.

[John Cribbin]

OK, I'm bored as well so I'll play!

Your signal chain comprises, guitar, lead, amp. So you need to eliminate two items before you identify the one that's giving you the issue.

My first port of call is the connectors, clean the cable plugs and the in/out sockets, dirt/corrosion are common culprits.

Have you a spare cable to try? They can break down and cause issues.

Different guitar/lead into the amp may help remove that as the cause of the hum.

Can you try the setup in a different room? Transmissions from electronic items can be picked up and end up coming out the speaker.

Is the bass active of passive? If active change the battery.

That should get you started ...

[chyc]

Thanks. This only happens on the one bass and I'd be surprised if it were outside the bass if turning volume to 11 makes it disappear but anything under that makes it buzz.

It's an active bass but has a passive bypass. Both buzz at lower volumes.

 

I've had buzzing issues before but nothing like these symptoms.

[geoham]

While some of John's advice may defy logic - like why would moving to another room have an impact if it's only one bass - it's always worth a bash to narrow things down as much as possible.

I was getting some weird noises on my Lakland,  not on other basses. I moved to another room and they were gone. I eventually discovered that I'd get the noises if a Powerline adapter was plugged in within the same room.  (They use electrical wiring to extend ethernet networks)

Regarding the buzz - assuming you have indeed isolated the fault to the bass - I'd suggest checking all the earth points are connected, particularly at the volume pot. Turning the volume down should bleed a part of your signal to earth - if it's not earthed properly it may lead to this problem.

A visual inspection is a good start, but if you have access to a multi-meter, then use it to check continuity between earth points.  (off the top of my head - black wires from pickups, back of pots, bridge,  sleeve connection point  at jack socket)

I'd also be interested in finding out whether touching the strings impact this at all.

I hope this helps - let us know how you get on.

George

[chyc]

Thanks both of you. I've tried all pemutations I can think of from your suggestion, putting it in another room, another power supply etc. It still persists, *except* on one amp. When I run through an Acoustic Image Coda R there's no buzz! I cannot explain that unless there's some amazing wizardry inside the Acoustic Image that doesn't feature in other amps.

I've opened the bass up to look for loose cables. It looks very clean and nothing jumped out as being wrong. While she was open I tried some contact cleaner on the volume pot. Did nothing. As you suspect touching the strings does make it better, even if not completely getting rid of the problem. While open I plugged the bass in to play. I wasn't able to make the buzz go away by  wiggling any cable. However, I was able to make it much worse by just touching the white cable leading from the volume pot direct to the jack socket. This was touching the outer sleeve rather than the copper, which surprised me a lot.

I should have said in my first report that the bass is dead silent at both 100% volume and 0% volume. It's around 50% that it's at its worst.

I don't have a multimeter to hand so I think it may be starting to get to the point I need to bring it into someone who would make it better by inspecting it rather than me who's making it worse.

I tried to take pictures but nothing came through with any clarity that I think anyone would find useful.

Thanks for your suggestions so far. Very helpful.

Edited November 26, 2020 by chyc