Buzzing (stops when touching bridge)

[Bay Splayer]

I play a Squier 70s vibe jazz bass that only buzzes when I play through my pre-amp pedal. That said, when I touch bridge or jack the buzzing stops. 

Thanks in advance for any information. 

[Bigguy2017]

Does  your pre-amp pedal run off a plug-in DC supply?

If it's a regular double insulated power supply it's not earthed (probably has a plastic earth pin), so there is no path to earth.

Touching the bass's metal work earths it via your body, and stops the buzz...  Normally the pre-amp would plug into a power amp and that would be earthed.

 

Take a piece of single wire and touch it onto the pre-amp's casing (if metal) or jack socket - touch the other end on something grounded .

If this cures the buzz you could plug a cable into a spare pre-amp out (?) and ground the cable's screen to some nearby piece of kit.

 

[Hellzero]

For all these buzzing problems there's a very simple solution. This cable :

https://www.bassdirect.co.uk/bass_guitar_specialists/Aero_DBuzz.html

Seems expensive, but what it does is simply amazing.

Edited April 13, 2021 by Hellzero
Missing word

[Bay Splayer]

Thank you both for your replies. 

[rmorris]

On 08/04/2021 at 10:33, Bigguy2017 said:

Touching the bass's metal work earths it via your body, and stops the buzz...  

Sorry but No. In general 'you' ie the bassist is not independently connected to 'Earth' so touching the strings / metalwork does not 'Earth' it. It's the 'other way round' basically. The strings/bridge are connected to 'Earth' (typically via amplifier or mixing desk) and touching them connects you to 'Earth'. This stops you acting as an antennae for interference - typically mains (50 Hz in UK/EU) and related harmonics.

To illustrate this - whilst not touching the bass metalwork - touch anything else that is 'Earthed' - eg typically the chassis of an amplifier or mixing desk etc and the 'buzz' will disappear or at least attenuate. (May need to wet finger and/or find a good contact point).

Essentially you are acting as an antennae for interference and connecting yourself to a defined low impedance point - typically 'Earth' - stops this happening. If you weren't near the bass/pickup this wouldn't happen - but it's rather difficult to play the bass from a distance 🙂

I've put inverted marks around 'Earth' deliberately as there's no particular significance of the planet to this - the connection to the 'Earth' is basically a safety issue - not a 'noise/interference' issue.

What is important is a connection to a defined low impedance node. That is typically 'Earth' or screen in a typical setup with '3-pin' mains connections - but may simply be a connection to a '0V' or 'Ground' connection where there is not an 'Earth' connection. eg battery powered setups.

Think about it - Aircraft electronics need screening but there's clearly no direct galvanic connection to any planet. (Yes - I do know that there is a characteristic rf impedance of free space to Earth - 365/366 Ohm but I stand to be corrected).

Apologies if this message seems a bit strident - a product of trying to educate mechanical engineers that proper screening really is 'a thing' and simply having continuity to 'Ground' isn't enough to get through EMC qualification 🙂

Cheers !