Room and bass specific humming/interference. Thoughts?

[solo4652]

I have a Harley Benton MV-4MSB Gotoh bass. It's a P/J bass, completely stock, as it arrived from Thomann, apart from different strings. I'm getting a huge amount of hum/interference from it, but only really in one room. I was starting to consider cavity shielding, extra earth wiring, fussing with pickup polarity and such like but, realistically, all that kind of electrical stuff is beyond my skill level or knowledge. But - do I actually need to do any of that? Here's the background:

 

Bass at home with 50W Eden combo - no hum or interference at all.

Bass at home with my practice rig - no hum or interference at all. Practice rig is GKMB500 into Tech Amp 12" 500w speaker. Completely dry signal path.

Bass at rejearsal room 1 with my practice rig - huge amount of hum, regardless of tone or volume settings on bass, or EQ on amp. I can just about find a room position where interference is reduced, but the moment I turn or move position, interference returns. I could use the bass as a radio direction finder! Room is a small classroom at a school - bit tight for a 5-piece band.

Other basses at rehearsal room 1 with my practice rig - no hum or interference at all.

Bass at rehearsal room 2 with my practice rig. A little hum and interference, but nowhere near as bad as rehearsal room 1. Rehearsal room 2 is a large function room at a local museum.

 

So, it seems that I'm only getting the hum/interference with the HB bass at just one room. 

 

[BigRedX]

Do you have either fluorescent lights or dimmer switches in the problem room?

[Bigguy2017]

I'd try a with wiring check plug at Rehearsal room 1 - It may have a missing earth   ;-(

 

[solo4652]

Flourescent lights - yes. Dimmer switches - no.

 

[solo4652]

1 hour ago, Bigguy2017 said:

I'd try a with wiring check plug at Rehearsal room 1 - It may have a missing earth   ;-(

 

Do you mean one of these?  https://www.screwfix.com/p/lap-ms6860d-16a-socket-tester-230v-ac/91596?kpid=91596&cm_mmc=Google-_-Datafeed-_-Tools?kpid=KINASEKPID&cm_mmc=Google-_-TOKEN1-_-TOKEN2&ds_rl=1244066&gclid=EAIaIQobChMIrOrqx-2LgAMVWJODBx2qNw5oEAQYASABEgJdIvD_BwE&gclsrc=aw.ds    

 

Wouldn't that just tell me whether a particular plug socket was faulty? I've tried 3 different plug sockets at rehearsal room 1 - same result each time of awful buzzing/interference. Also, I only get the problem with that particular bass, and not with either of my other 2 basses. 

Edited July 13, 2023 by solo4652

[Bigguy2017]

9 minutes ago, solo4652 said:

Do you mean one of these?  https://www.screwfix.com/p/lap-ms6860d-16a-socket-tester-230v-ac/91596?kpid=91596&cm_mmc=Google-_-Datafeed-_-Tools?kpid=KINASEKPID&cm_mmc=Google-_-TOKEN1-_-TOKEN2&ds_rl=1244066&gclid=EAIaIQobChMIrOrqx-2LgAMVWJODBx2qNw5oEAQYASABEgJdIvD_BwE&gclsrc=aw.ds    

 

Wouldn't that just tell me whether a particular plug socket was faulty? I've tried 3 different plug sockets at rehearsal room 1 - same result each time of awful buzzing/interference. Also, I only get the problem with that particular bass, and not with either of my other 2 basses. 

They could all be on the same ring main

[BigRedX]

29 minutes ago, solo4652 said:

Flourescent lights - yes

 

That's most likely your problem. Try again with them all turned off in the room, as well as any in adjacent rooms and corridors.