One end floating ground on cord between effects pedals

[Guitarist]

Though I have a toroid/isolated pedal power supply, there is yet noise—even bypassing pedals. So I'm wondering if any one else has tried swapping in custom cabling where one end of the ground is lifted? It's akin to where in an amp, you lift one end of the shield. It might not work or hum.
One of the pedals is a DOD and has the old 1/8 power jack, so that may an issue. Anyways I'll try/pull a few things and report back...what a pain!

[52 Bill]

If all of the pedals are grounded together by the dc power supply lines to one source, then the audio grounds can be lifted at one end of each cable. I've done this to eliminate ground loops.

If you do this be sure to mark the cables in some way so that you don't try and use them for normal uses.

[Guitarist]

OK, thanks I'll give it a shot...

[pinkjimiphoton]

what i did with my pedalboard was use mic cable, low noise 3 conductor and wired it so that one wire was hot, one wire was ground to both ends and plugs, but only connected the shielding on the "ground" side. seemed to make a significant difference in the noise floor. to make it idiot proof for myself, i tend to use right angle cables on the grounded side of long runs, like from my board to my amp and guitar to board. the short ones i mark the grounded/shielded side with a green wiretie so i don't forget. i never could seem to get the ground lift idea to work well for me, but this way the cords work normally but "telescope" the shielding the length of the cable... at least that was how my bud mike explained it to me years ago. if ya run into problems, it may be worth looking at. hope it helps.. peace

[Mick Bailey]

+1 on telescope grounding. Just make sure the screen is only connected to one end. There's an argument towards directionality of cables made up this way, but in my own setups I've not heard any difference in noise levels when swapping the grounded end around. I certainly think that this system works well.

[pdf64]

The Rane library is a fantastic resource for all sorts of info http://www.rane.com/library.html
Note #110 is the classic on this topic Sound System Interconnection

[pinkjimiphoton]

thanks mick, happy new years my friend!

i too have found reversing the cables to often be fine (but not between your guitar and a fuzzz!! instant antennae!!)

you can i think break up ground loops by doing so, as the ground will be referenced to wherever it attaches in the chain. can be really useful, and significantly
less rfi and noise.

[Guitarist]

Well, some success but I feel a bit lame. I swapped out a cable that Ω tested fine but wasn't working well enough. Eying a replacement from months back, an intermittent Planet Waves, I meeted it a healthy chop at the 90ø end and added a Switchcraft jack— but floating the shield at that end. PW tie both ends to ground. They use twisted mic-style cable.
I also X-Actoe'd their broken end apart to see what's inside. They've their own tech, but as the metal isn't very thick, the angled corner bit had snapped apart. Now fixed and tested at a jam last night, the rig was MUCH better. There is yet work to do though and the pedal-out, stereo leads to the rack amp will get upgrade soon, but those are low-Z anyways. But I have to engage the ground "lift" at the amp back panel yet. I wish that Carvin TS-100 was better made or that I still had my 100 lb. VHT (ach too heavy

Also, can I just test for continuity of the inner DC barrels to see if the PS grounds are isolated or not?
EDIT: Tested the PS output grounds and they are all isolated.

Anyways great help, thanks!

[pinkjimiphoton]

yeah, pw is right... both plugs should connect to both hot and ground. but the shield should only connect on one side. i had tried the cut the shield trick without, and never ever got it to work, or perhaps i didn't have an actual ground loop problem. lifting the shield on the non grounded side sends all the rfi and hash to ground. but lifting the ground connection as well never worked for me personally. glad ya got it sorted out.

as for your carvin.. be careful not to ,bump your pots... my experiences with carvin amps, tho they sound great, haven't been really too positive. lotta broken pots where they join the pcb... open it up to fix and break 4 or 5 more. that was years ago, hopefully they've improved their QC substantially.

even if the power supply sections are isolated, don't expect to be able to run pnp and npn pedals off them. even tho it seems like it should work if they are truly iso'd, they don't in my experience.

[Guitarist]

Things are still working great! Another guitarist was noticing noise swarm at home-space and we quickly clued intuit the rheostat-dimmer dials we 100% causing it. Killed it noise vanished for him.