How do I prevent being the source of hum?
 

So I recently changed out the pickups and preamp on my bass and installed an active/passive switch. At first try there was no hum anywhere. Then after a few minutes, there was some serious hum in passive mode. Everything else worked fine.

I left, and came back home a few hours later and tried it again, and then no hum whatsoever. I checked all of my connections/solder points, everything was wired correctly, nothing was loose, and I then figured that I was the source of the hum. This is not the first time it has happened with me.

How does this happen and how can I prevent it?

Wear an aluminium foil suit? Strange that you are the source!

Single coil pickups do hum. It can be minimized by moving around, changing the axis of your body relative to the amp. Sometimes the electrical source can exascerbate the problem. Were there other things plugged into that circuit?

It was a circuit comprised of my bass plugged into my headphone amp along with my headphones and iPod. But I had the exact same setup later on in the day when there was no hum. The pickups I installed are Delano dual-coils.

He's talking about the electrical circuit. If there are other outlets connected to the same circuit breaker, anything connected to them could be the source of the hum as they are part of the circuit. Look at everything that changed over the course of the time you were playing, and eliminate the changes.

It can also be induced noise from electrical fields in the room. Dimmer switches, fluorescent lights, even a furnace or A/C fan with a defective motor can cause hum, without you being plugged into the same AC outlet.

The only thing I can think of is that I had my iPod plugged into a charger on the wall. Later on that day I no longer had it plugged in. I'm thinking this was probably the issue. Thanks for pointing that out. I'm obviously not educated in electronics/circuits and all of that stuff. Interesting....

OP, you weren't the source. You were present once without hum. One of the previous answers is probably correct.

Electrical fields are weird. When I turn on my microwave, my son loses his wifi connection but I don't.

Good luck!

Chargers are a terrible source of hum, so that could well have been the problem.

Ceiling fans can cause you problems too.

If it's portable, take it outside in the middle of the yard and see if the hum still there.

It might be that, it might be something else in your home or if you live in an apartment it could be something a neighbor was doing. Hum is a word that some of use indiscriminately and some of us use with precision. The precise definition of hum is the pickup of 50/60 Hz magnetic fields from equipment running off AC power outlets. This hum is coupled magnetically so the pickups on your guitar which are by design sensitive to magnetic fields will pick up this kind of interference quite well if it is present. If you turn off the source of the magnetic fields the hum goes away. So the situation you describe, hums sometimes and not others is quite normal. Single coil pickups are sensitive to this but humbucking and hum canceling pickups are cleverly designed to reject this kind of interference. Anything with an AC power transformer in it is going to generate hum if you get your single coil pickups close enough to it because transformers operate by generating strong magnetic fields. They try to keep those fields inside themselves for maximum efficiency but there can be considerable leakage.

Other types of interference are called buzz or anything but hum. They may be magnetically or capacitively coupled and they are either at frequencies that are not related to 50/60 Hz or else are very high harmonics of 50/60 Hz, high enough so they don't sound like the rich bass note of hum. Capacitively coupled buzz can be stopped by shielding and either kind of buzz can be stopped by filtering if it is high enough in frequency so that the filter does not disrupt your bass's tone. Once again if you turn the source of the buzz on and off it will come and go. These days high efficiency lighting circuits are a common source of buzz and depending on the venue they may be unavoidable so shielding and filtering may be required. Now your body can enhance the capacitive coupling of buzz to your bass but if your bass has a ground wire to the bridge as it should you can stop this by keeping a hand on the bridge or the strings. That tends to happen naturally when you are playing!

Strictly speaking neither hum nor buzz can be coupled to your bass through the power lines. But your AC powered amp can get infected with buzz this way. An amplifier should be immune to AC coupled hum because it has to operate while connected to a HUGE 50/60 Hz voltage source. If the filter caps in the power supply start to fail your amp will hum but that won't come and go it will just get worse and worse until you fix it.

Ken

Thank you for this thorough explanation. It makes perfect sense.

try singing instead :hiding:

LOL! With my luck, I'd probably make the microphone hum.

Were you in the 'Vacation" movies?

I bet you figured it out

RE: How do I prevent being the source of hum?
 

Learn the words?



No need to thank me!

Dan K.