Ground loop hum from Korg DTR-1 tuner

[warlok]

Well, I picked up a used but in mint condition DTR-1. Works perfect as far as tuning, tracks fast, and is perfectly accurate. Signal is Guitar>DTR-1>RM100 input... Serial loop send>ValveFX>serial loop return... Parallel loop send>M108 EQ>Parallel loop return. Everything is plugged into my Furman PL-8 and even with no cables plugged into or out of the tuner, it makes a pop when I turn it on/off. And there is a pretty bad 60 cycle ground loop hum when it is hooked up. Seems from threads/reviews on the net that the hum is a popular issue with these. Ive seen fixes from using a 3-2 prong plug adapter (get rid of ground plug), remove the internal chassis ground, nylon washers between unit and rack rails, hum eliminator (ebtech), another pedal before the tuner to buffer the signal, or some output to tuner not coming back into the signal chain.

Does anyone know the specific reason for the these units causing this and what the correct fix is? If I can't fix the issue correctly, the only fixes I'm willing to try from that list are the nylon washers isolating the unit from the rails (doubt it), ebtech hum eliminator (have one in the closet, but doesn't fix the root cause), or switching my M108 EQ for my KFK EQ (stereo outputs) and using one side for the signal chain and one for the tuner out (should completely remove it from the chain, still doesn't fix root cause..)

[Twitch]

even with no cables plugged into or out of the tuner, it makes a pop when I turn it on/off. And there is a pretty bad 60 cycle ground loop hum when it is hooked up.

That right there tells me it is definitely the tuner or the Furman. Any crap that comes down through any of the units connected to the Furman should be filtered out by the Furman, thats its job. However, the fact that the only unit causing hum or causing the pop is the tuner, makes me think the tuner may have an issue as well. As to what to do about it, maybe try get a hold of another Furman and see if it does the same thing. Same with the tuner. Ground related problems can be quite hard to diagnose sometimes. Taking the ground out of the equation could solve the problem, and if it does then you have two choices, go with it and know that without a ground attached to it, both you and the unit could experience damage.

[warlok]

I'm thinking the best bet for the hum would be switching EQ's. They're the same exact thing except the second output. Using that output and not coming back into the amp can't hurt anything I guess. But that pop bugs me. Gonna try taking it out of the rack, isolating it from the rack rails that everything is attached to. Maybe it could be a short through the chassis ground and going through everything else attached to the rails?? Makes sense in my head.. If it still does it, then I know it's through the cord at least..

[Twitch]

Gonna try taking it out of the rack, isolating it from the rack rails that everything is attached to. Maybe it could be a short through the chassis ground and going through everything else attached to the rails?? Makes sense in my head.. If it still does it, then I know it's through the cord at least..

Actually, that makes perfect sense. The metal rails touch the chassis of all the equipment and since the chassis are grounded, you will have all their grounds conected because the metal rails. That would be a very effective troubleshooting test. And then if that solves the problem, put some plastic washers between the tuner ears and the rails when you put it back in, problem solved.

[warlok]

Exactly!!

[warlok]

Well, kinda figured out that the pop when I turn it on/off is normal as it happens with everything. Even my monitors/mixer/interface recording setup.. Just never really noticed it with anything else as I have the amp on standby when I turn everything on/off. So that's not an issue anymore..

For the hum, found that if I put the tuner in the parallel loop before or after my EQ, it works fine with no hum. And if I need to tune something during setups, etc., I can just plug into the front "Input 1" and it takes precedent over the rear inputs and I don't have to fire up my whole rig just to tune a guitar.. May switch to the KFK for the extra output but all is right with the world now..

Thanks Twitch!!

[Twitch]

No prob. Glad I could help.