Trying to identify an intermittent noise caught by instruments pickups

Problem's source is outside the instrument. Check this passive single coil pickup JB bass at another location. If this special noise disappears you can continue to search it at your location :)... It is not 50/60Hz AC hum, but kind of EMI/RFI (high frequency initiated) noise. Can be radiated by something digital controlled - fridge, hot water boiler, alarm system etc. If there is a difference of noise level touching strings/bridge (grounding yourself) - it means instrument is not shielded, or weak/wrong shielded, or shields are not grounded at all, or wrong grounded. All it is more or less typical for most even much higher priced pro instruments. This industry is very conservative, still living in 50'... Solution is total shielding of instrument's electronics (cavities and pick-guard), including shielding of pickup coils and careful grounding of all metal parts - including pickup poles. I can suggest grounding even of neck plate, truss rod and all screws located close to the pickups. It is not so easy to do (some case rather tricky) but no another way. Even inside the instrument grounding must be done without ground loops, shields can be connected parallel or/and serial to ground but never twice or more. Signal and shielding grounds must be grouped and separated until output jack. However - some part of the noise problem can come from the low quality guitar cable with bad shielding (not 100% covering), or damaged cable's shielding (physical/corrosion/oxidation - resulting in higher resistance). All the not shielded or weak/wrong shielded guitar parts (including cable) are working like high frequency interference "antennas". Total shielding will reduce AC hum noise too. Plus - put ferrite clips/beads (inductive HF filters) at cable's both ends, it will reduce the HF problem too. *Using ferrite beads on all cables and wires (including AC, speaker, signal, control etc. - all connected to your active and passive gear) is the best idea this "noisy time". This is long talk/story, but most case result is surprising good.
 
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Sorry, didn't read through all the replies in depth....

Have you tried it without the DI? Straight into the interface?

Does your interface have a separate power supply so you're not running off the USB buss power? Can you run the interface with the PC off?

Did you try a different instrument?

can you add foil to the underside of your pickguard and pick up cavities?

Is the bridge on the guitar grounded? Should be, but check.

The noise is digital. Maybe from your PC, but I'm guessing it is a radio source somewhere nearby.

The cable looks weird, not like a regular guitar cable. It looks short and less flexible than I would expect from a guitar cable. Are you sure it's shielded?
 
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