Bass hum, who's responsibility?

[jazzyvee]

I tracked a frustrating hum problem back to my broad band over mains powerlines adaptor. When I turned it off the hum and crackling stopped.
. http://www.pcworld.co.uk/gbuk/networking/networking/powerline-home-networking/devolo-9131-dlan-500-duo-500-mbps-powerline-adapter-kit-twin-pack-21376659-pdt.html

If you also have one of those things or the ones for sending media down the mains you could try turning off.

Jazzyvee

[Grangur]

[quote name='jazzyvee' timestamp='1379152290' post='2209145']
I tracked a frustrating hum problem back to my broad band over mains powerlines adaptor. When I turned it off the hum and crackling stopped.
. [url="http://www.pcworld.co.uk/gbuk/networking/networking/powerline-home-networking/devolo-9131-dlan-500-duo-500-mbps-powerline-adapter-kit-twin-pack-21376659-pdt.html"]http://www.pcworld.c...376659-pdt.html[/url]

If you also have one of those things or the ones for sending media down the mains you could try turning off.

Jazzyvee
[/quote]
It sounds like you could need to think if there's anything in your house you've only just turned on that wasn't in use for the first 10 days... the heating maybe?

You could also try wiring a 13A plug with an [b]earth cable only[/b], then try touching the other end of the earth cable to all the exposed metal parts of the bass and see if the hum disappears.

[discreet]

[quote name='uncle psychosis' timestamp='1378982066' post='2207259']
The human body is a massive antenna for unwanted electrical noise. This noise is picked up by poorly shielded pickups and so you can hear it.
[/quote]

Simply stay at least 10m away from the bass. Hey presto - problem solved.

Edited September 14, 2013 by discreet

[rmorris]

[quote name='uncle psychosis' timestamp='1378982066' post='2207259']
Not this again.

Noise goes away when you touch the strings because you're grounding *yourself* not because you are grounding the strings.

The human body is a massive antenna for unwanted electrical noise. This noise is picked up by poorly shielded pickups and so you can hear it. When you touch the strings you ground yourself and the noise goes away.
[/quote]

+1 That's basically the way it works. The strings / bridge / metal on the bass is connected to mains earth / ground all the time. But your body isn't until you touch the strings / bridge. Your body acts as an antennae for electrical noise and if you are near the bass but not 'earthed' then that noise can be picked up by the pickup.
When you touch the strings or bridge you 'earth' yourself and the noise is shorted to earth ( slightly dodgy technical explanation but you get the gist or textbooks are available :-)
To illustrate - if you weren't near the bass it wouldn't pick up noise from you. If you moved toward it then noise pickup would increase but then (more or less) disappear when you touched the strings.
In fact - you get the same effect whether you touch the strings / bridge / or anything else that is 'earthed' - jack plug shell / earthed rack unit chassis etc.
Worth bearing in mind that degree of noise pickup is basically related to the impedance of the pickup. Higher Impedance = More noise pickup. Hence why low impedance pickups ( active EMGs for instance) can get away without string / bridge ground /earth connection.

wrt the OP's question here I'd suggest taking it back to the shop environment to try ; think about any electrical changes at home esp broadband over mains ; bear in mind that problems can come from floors above/below and neighbouring properties ( brick and plasterboard etc are fairly transparent to electrical noise interference !)

Hope you get it sorted or have done already.

Edited September 14, 2013 by rmorris

[stingrayPete1977]

[quote name='Ou7shined' timestamp='1378977584' post='2207197']


Don't you just hate it when a bass is fine for weeks then suddenly overnight the shielding lacks.
[/quote]
Actual lol moment!

[stingrayPete1977]

I have had this on lots of basses especially new ones, the earth behind the bridge sinks into the soft paint, peel it out clean it and move it to a fresh area before screwing the bridge on tightly and its gone. Why and how it hums I will leave to the experts but all I know is I have had that exact problem 3 times at least!

[bassix]

Well I have now visited the shop and they were very helpful, interestingly the amount of hum varied dependent on which amp I went through. They have agreed to inspect the bass and resolve any issues. Equally strangely I went to band practice today and had no issues with hum.

[discreet]

[quote name='bassix' timestamp='1379268490' post='2210639']
...I went to band practice today and had no issues with hum.
[/quote]

Which points to it being an environmental issue rather than a specific problem with the bass.

[stingrayPete1977]

[quote name='discreet' timestamp='1379269742' post='2210657']


Which points to it being an environmental issue rather than a specific problem with the bass.
[/quote]
I'd say its still the bass but the amp and eq just highlight/mask the hum.

[afterimage]

Don't. Forget mains filter tooi had a dimmer switch that caused similar problems. At home

[rmorris]

[quote name='stingrayPete1977' timestamp='1379266413' post='2210595']
I have had this on lots of basses especially new ones, the earth behind the bridge sinks into the soft paint, peel it out clean it and move it to a fresh area before screwing the bridge on tightly and its gone. Why and how it hums I will leave to the experts but all I know is I have had that exact problem 3 times at least!
[/quote]

if the ground connection to the bridge strings becomes disconnected then you can expect noise regardless of whether you are touching the strings or not. In fact might be worse when you touch strings as they are connected to your body and close to the pickups.

It can get complicated though as a connection might be made but have a significant impedance. Even if there's no dc continuity ( meter doesn't buzz ) there may still be some continuity at ac due to capacitance.
Anyway - you really do need to make sure that everything that should be connected to ground is connected solidly.

[rmorris]

[quote name='afterimage' timestamp='1379276224' post='2210794']
Don't. Forget mains filter tooi had a dimmer switch that caused similar problems. At home
[/quote]

yeah - lighting dimmers can be evil noise generators. And mains filters won't necessarily help as noise is radiated (as well as conducted back through the mains wiring ).
Shielding can be fairly ineffective too due to the frequency. Only real solution is low impedance and/or hum cancelling pickups together with low impedance balanced electronics. 'Starquad' cable might be useful too in extreme or critical cases but this is more typically an issue for the PA soundpeople...