Korg Forums

[brent]

I'm getting a 60 cycle hum on input 1. I noticed this started happening suddenly while my rig was on and I was working on the computer. It started to hum.

Here's some characteristics of it.

Input 1 = 60 cycle HUM with guitar volume up. There is no hum with the guitar volume turned down. Hum occurs if plugged into the back or into the front of the unit on input 1.

Input 2 = no hum regardless of volume. It's quiet as a mouse.

I've replaced all 4 capacitors in the unit, just as something cheap and easy to try. This change had no affect (positive or negative) on the unit.

Any electronics buffs out there got a solution to this? Seems like it might be interference from the front jack and the AC power? Why would it start suddenly? Possibly an issue with the transformer? Help! Thanks!

[ebassotti]

Hello Brent (thanks for your reply on the other thread ),

Since you mention working on the computer, is there any connection between the amp/rig to which the DTR2000 is attached, and your computer? If there is it might be worth making sure there isn't a ground loop involving the two systems. Although - just like in the case of a transformer issue - the next question would be why it would only affect input 1.

The other thing that comes to mind is a ground loop within the DTR2000. I'm not familiar with its internals in any way (haven't opened mine and not going to while it's still under warranty) but the jack in question could somehow have gained undue contact with the chassis. I know it's a long shot, but I've experienced a similar problem with a GK 2000CPL preamp in the past, where a plastic jack had been replaced by an uninsulated metal one.

[brent]

Ya, thought I'd report back that I've resolved the problem. I made a new cable. I'll do my best to describe the problem and my solution.

So if you open your unit, you'll see there's a left and a right side printed circuit board. Front of the unit facing you, the right side has the AC power from the wall and also input 1 along with the mute phono jack. The cable in the picture is responsible for taking the signal to the PCB on the left side where some of the processing is done (as is the rest of the inputs and outputs). I know you mentioned you were reluctant to open it due to warranty void, etc.. I totally understand, this is just FYI stuff.



So, the picture shows two cable ends. Cable left is the factory cable (the one with the orange wire). The ORANGE wire carries INPUT 1 signal! Cable right is my cable I made after purchasing some nylon connectors and pins. Using the right crimp tool, I took some Belden shielded cable and crimped up a new cable. The drain wire connects to the ground on the cable. I could go into more detail, but basically... the once unshielded orange wire is now shielded as it passes by the power transformer and AC current.

If you want to test your system to see if you have the same issue. Simply plug the DTR-2000 into your amp (nothing in the inputs). Crank the volume on your amp to exagerate the possible issue and switch the tuner from input 1 and input 2. See if you hear a noticable noise difference between input 1 and input 2. I'm curious to hear your results. Also, I'll send you an extra cable I made if you want.

-Brent

[ebassotti]

Good to hear that you were able to solve the problem, and thank you for your generous offer!

I'm going to send you a PM.