super stupid aby box question

[pinkjimiphoton]

i warned ya... extra special crispy stupid question,...
if building a passive a/b/y box, if you're getting ground loop noise, can you use big freakin poly caps in line with the audio to block the dc hum potential?

i was thinking about it, and figured since caps block dc but not ac, it may be a quick-n-sleazy way to get around ground loop issues without messing up the tone too bad... i was thinking somewhere in the order of 470n to 1uF orter do it, at least for a guitar...

am i crazy? do ya think this would work? stoned musing? it seems to me like it could maybe help quiet stuff down a wee bit... kinda like blocking caps in amplification stages...

you may say i'm a dreamer.....  but sometimes stupid ideas lead to something kinda cool... thoughts/rebuttals/education appreciated!!!!

[MaxPower]

nevermind

[vigilante397]

What layout are you using for your A/B/Y? I have to admit I've never had hum from a passive circuit.

[thermionix]

Lift the ground on one of your amps.  Loop gone.  Ground lift adapters are like a buck each.

[bluebunny]

Hum is AC, otherwise you wouldn't hear it.   

[pinkjimiphoton]

like i said, just a stupid question.

i built a simple a/b/y box from a schematic i found on GGG. works fine. as long as everything is plugged in, anyways. no hum whatsoever.

i was just curious if it would work sorta like  iso transformers is all, to "float" the audio to the tips of the jacks.

dumb question, but i figured i'd never seen it asked so i would. now i know why.

[blackieNYC]

Use an ISO transformer.  Get one of those edcor transformers- less than Jensen, nice piece of iron, and full guitar audio spectrum. Don't lift the ground on a tube amp. I mean, maybe as a test - then you'll know if that's your issue.
Also, if the amps are on one AC (120v, 220v, etc)circuit, sometimes this loop buzz isn't very much at all.

[pinkjimiphoton]

i'm actually good bro, i was just wondering if it would make a difference.

i thought the hum was dc, i didn't realize it was ac... so i thought a cap would block it.

the box i built is actually dead silent, and i am not worried about ground loops... it switches the output of my pedalboard between the input to my 44 mag to drive my talkbox, and my delay to feed my amp after all the other crud i use.

i have no problems with it, i was just wondering if it would work, is all. i agree on the transformer.

lifting the ground on one amp is something that should NEVER EVER EVER be done. when you're told to lift the ground, it should be on the audio cable, not the power supply.

and if ya have enough issue to need to lift it on the audio, you should fix the actual problem itself instead of putting a bandaid on it imho.

i DO agree with using 3 conductor mic cord however... hot and cold, and only connect the shield to the plug at closest to ground potential. works out great and can drop your noise floor about 6db

[vigilante397]

lifting the ground on one amp is something that should NEVER EVER EVER be done. when you're told to lift the ground, it should be on the audio cable, not the power supply.

+1

[thermionix]

lifting the ground on one amp is something that should NEVER EVER EVER be done. when you're told to lift the ground, it should be on the audio cable, not the power supply.

+1

Meh.  Ground is ground is ground.  Either way you do it, same result.  Just gotta be careful the order in which you hook things up.  Signal cables first, then plug in to AC power.  Sometimes its much easier to use a ground lift adapter, especially when simply linking two amps via input jacks.  If you build a Fender 6G15-type standalone reverb, or other AC-powered effect, you use a 2-prong AC cord, right?  Same thing.  But if you're building a custom ABY box, no reason not to lift the ground there, if it works with the circuit.

[blackieNYC]

A little reverb never killed nobody. Can't generate enough current.
I used to put a ground lift on one of two 100watt tube heads.  Back when I was young and didn't know better.  Purely lucky with it. Not recommended.  If there is some kind of short, and all that current can't find a path to ground through the AC cable, it will find a ground path, which may involve you.

[thermionix]

But there is a path to ground.  Through the shield of the instrument cable(s) to the chassis that isn't ground-lifted...

[pinkjimiphoton]

don't mistake telescoping the shield for lifting the ground. two different applications. if you lift the shield and ground on one end that is the only way to lift the actual ground.

and believe me, getting bit by a big old ferocious tube amp like my old ampeg v4 was no fun. bad grounds are not something to play with. i was lucky last time and didn't get hurt, but it roasted the passives in my guitar. i was afraid of getting bit by a microphone. so i just barely touched the end of a string to it and saw white light. not fun. turned out some hipster had added a ground lift plug to the cable running to the stage, and some other hipster, after tripping on it plugged it in backwards. in that case, shortest route to ground would have been me if i had touched the mic instead of letting my string touch it.

[thermionix]

I've been hit by plenty, believe me.  Worst was 100W Super Lead B+ on one hand, other hand resting on chassis.  Dumb!  But the scenario you outline with the V4 and mic is a different situation than what I was talking about above.

[vigilante397]

100W Super Lead B+ on one hand, other hand resting on chassis.  Dumb!

You're lucky to still be here! The one-hand rule saves lives.

[thermionix]

You're lucky to still be here! The one-hand rule saves lives.

Yeah no kidding!  It was about 18 years ago, so I reckon I pulled through.  Now sometimes I'll find myself cooking in the kitchen or something like that and my left hand is behind my back.