I occasionally gig with a local singer-songwriter. On one such gig, I was to be on lead guitar and when we rehearsed in the BL’s front room, the bass player was getting noise through his old-school Class AB combo (can’t remember what, but not Ashdown). After our rehearsal I volunteered to take a look at it, so we heaved it into the kitchen so that I could get the chassis out and onto the table.
The amp worked fine in the kitchen. We identified the source of noise as the BL’s wireless router.
There are plenty of old bass amps either designed or built in the 90s that are still being gigged today because of their perceived sonic heft, and despite their physical heft. Far fewer people back then had WiFi at home, so it wasn’t something designers had to address.
Also I think getting your gain staging right may help to reduce background noise.