Help understanding hum removal techniques.

[Travis]

The tip from the DC jack (ground) is wired to the input jack ring. When the input cable is connected, the ring connects to the sleeve and it is star grounded.

[OasisMcFly]

Okay. I'm not sure the shorting jack stuff applies to my present predicament. Are you guys suggesting I should switch the jacks to to make them shorting?

On a different note, I had no clue that it was best to keep the power and ground as close together as possible. It makes total sense when I think about it, but I had just never given it too much thought. I guess this is why I see some builds where the power and ground wires have been twisted around each other.

Also, I've got some shielded wire on order, so I will try that suggestion as soon as it arrives.

In the meantime, I was interested in clarifying one of the other suggestions I found online. Several places I saw suggested adding in a resistor on each jack, essentially connecting the tip to the sleeve. Wouldn't this change the tone of the pedal? And would it not need a cap as well, to make it more of a high or low pass filter?

[induction]

OasisMcFly wrote

Okay. I'm not sure the shorting jack stuff applies to my present predicament. Are you guys suggesting I should switch the jacks to to make them shorting?

No. That was a digression. Doesn't apply to your problem.

In the meantime, I was interested in clarifying one of the other suggestions I found online. Several places I saw suggested adding in a resistor on each jack, essentially connecting the tip to the sleeve. Wouldn't this change the tone of the pedal? And would it not need a cap as well, to make it more of a high or low pass filter?

This sounds like a terrible idea. It will not only change the tone of the pedal, it will change the bypassed tone as well. And I can't see any reason it would solve your hum problem. Can you provide a link to this suggestion? I'd like to know what they're talking about.

[induction]

I just noticed this:

When I take it straight into my pod, I have no issues or hum at all.
...
When the pedals are bypassed, the hum is considerably less, but not altogether gone. However, if I remove the 5 pedals I made from the chain entirely, the hum is inaudible except at extreme volumes.

The fact that you are getting hum in bypass, but not when the pedals are completely removed indicates a few possibilities:

One possibility is oscillation in bypass, but I can see that you have grounded the circuit inputs in bypass, so that is unlikely to be the cause. Have you used the same bypass wiring for all of your pedals?

Another possibility is a poor ground connection somewhere in the chain. You can check this by connecting all of your pedals and looking for continuity between the grounds in the first and last pedal in the chain. Check the grounds at the jacks and on the circuit boards. Since you say that the hum isn't there when your commercial pedals are in the chain but your DIY ones aren't, this one is a real possibility.

Another possibility has to do with your POD. Being digital and current hungry, it may have the tendency to inject noise into the mains wiring, which could infect the ground voltage of anything on the same mains circuit. For example, I can't use my Whammy IV at all because when I plug it into the wall, my amp starts to hum. This happens even if the Whammy is not in my pedal chain, just plugged into the wall, sitting alone by itself. If I recall correctly, it might even happen when just the adapter is plugged into the wall, but not into the Whammy. The hum is bad, but it gets worse when I turn on any pedal that has a gain stage. This one is a real possibility, but I don't see why this wouldn't cause trouble with your commercial pedals as well.

Can you try your pedals into a real amp, just as a test? We need to see whether the hum is actually coming from the POD or the POD's power supply.

Two final questions: does the setting of the Sag control on the Barbershop have any effect on the hum? Is the hum any worse with the single coil than with the humbucker?

[Sensei Tim]

a few other questions:

are you playing in a room with fluorescent lights?

when you're playing them do you have the back plates on?

does the hum go away or diminish when you touch your guitar strings with your fingers or if you touch the stomp switch with your finger?

if you switch guitars does it still hum? do you get equal amounts of hum when you switch between bridge and neck pickups?

have you tried using shielded wire?


a good rule of thumb when routing wires is power lines should cross signal lines at 90 degrees. try not to run power lines parallel to signal lines.

with that many dirt pedals all on in a row, you're going to amplify the noise as well as the guitar signal.

[Beaker]

Any luck yet mate?

I can tell from your first post that you have done your homework, but the internet has as much bad information as good information.

The suggestions so far are all good ones, but bear with us, and take things one step at a time.
Hopefully we won't get too sidetracked.

Just a note on Induction's suggestion about the POD, my son had a similar issue in his studio when he got a new laptop. The power supply for it caused havoc, inducing hum in a whole heap of other equipment. It took us weeks to sort it out!

[OasisMcFly]

As it often does, Life got in a way a bit. I haven't had any time the past couple of days and it looks like it will be early next week before I get any real time free. I am definitely not done with this topic though. Also, I have some shielded cable on order that should be in soon as well, so I can try that suggestion out.

[motterpaul]

I have one outlet that gives me oscillation all the time (from power supplies for pedals or mics), because of something else plugged into it (my solder gun? I don't really know) - but if I change outlets it is much cleaner, Its not always the pedal.