Dreaded mains hum again.

[jazzyvee]

I've been practicing with my series I guitar today for a last minute gig tonight.
I'm using a my Fender "The Twin" amp tonight which always has a bit of hum. Anyway when I plug my DS-5 output into it the noise gets really louder, this happens whether the 5 pin cable is connected with or without the guitar. It does not get any louder when the guitar is plugged in. I have tried a rack unit, a blue box unit and both have the same issue.
Initially i thought the hum was coming from my new power supply for my pedal board but when i removed the pedal board and plugged directly from the DS-5 to the input jack the hum was just the same. It is quieter when in the second amp input socket. But too loud to use on a gig.
So i've decided to use the jack cable instead for the gig. Put some batteries in the guitar, plugged in and no noise above the general hum of the amp.
Any ideas?

[lbpesq]

On short notice?  Bring extra batteries and a screwdriver!   Good luck with the gig.

Bill, tgo

[JimmyJ]

Sorry you're having hum problems.  You're not using one of those George L cables from the DS-5 to the amp are you?  This almost sounds like a ground loop problem but that shouldn't be happening - especially over there in 240V-land where you can't just "lift" the mains ground.  Hopefully there is no voltage potential between your amp and your DS-5...

If you want to pursue the issue further (not for tonight's gig!) you could look into trying something like this:
https://whirlwinduk.com/iso1/

I had a friend whose guitar rig had a very complicated signal path with a lot of gear involved.  He carried with him two homemade audio isolation transformers which he could insert in the chain at any point.  And the weird thing was, the insert point which killed the hum was often different from gig to gig.  But that was a handy box to have along and usually solved the problem.

Jimmy J

[jazzyvee]

On short notice?  Bring extra batteries and a screwdriver!   Good luck with the gig.

Bill, tgo

Yep, i bought some new batteries at a local shop on the way. The batteries i put in the bass were also new. Because I don't gig much with the guitar I don't tend to leave batteries in there.

[jazzyvee]

Sorry you're having hum problems.  You're not using one of those George L cables from the DS-5 to the amp are you?  This almost sounds like a ground loop problem but that shouldn't be happening - especially over there in 240V-land where you can't just "lift" the mains ground.  Hopefully there is no voltage potential between your amp and your DS-5...

If you want to pursue the issue further (not for tonight's gig!) you could look into trying something like this:
https://whirlwinduk.com/iso1/

I had a friend whose guitar rig had a very complicated signal path with a lot of gear involved.  He carried with him two homemade audio isolation transformers which he could insert in the chain at any point.  And the weird thing was, the insert point which killed the hum was often different from gig to gig.  But that was a handy box to have along and usually solved the problem.

Jimmy J

As I was writing this I had a feeling you would ask about the George L cables. Actually it wasn't a gig were I needed my pedal board so I just took three pedals but only used one and wired them with regular patch cables.
Would it be possible to try that idea using my Radial Pro DI passive box to do the same thing with a DI to jack adaptopr on the output.

[JimmyJ]

... Would it be possible to try that idea using my Radial Pro DI passive box to do the same thing with a DI to jack adaptopr on the output.

That's not exactly what your Radial was designed to do but you could try it as an experiment.  I expect you'll lose a lot of level though because a DI's transformer is a "step-down" affair whereas that ISO box above is a 1:1 winding.  Plus, I think technically you'd need to use pin-2 and pin-3 of the XLR as your +/- audio signal and keep pin-1 and the chassis of the box isolated from the amp.  So it would take a bit of trickery.

Jimmy J