'Buzz' or 'Hum' when recording.

E

Eddzz!!

New member
A couple days back I bought myself a small recording setup for some radio work I do at University. Included in this setup is an Alesis MultiMix 4 USB mixer and an SE Electronics se2000 microphone. Now since using it, I've been both over the moon with sound quality and incredibly infuriated by an annoying hum that is occurring more than often now.

Here's a sample of the buzz. Annoying microphone buzz

I've gone through several procedures of removing the buzz and have succeeded on occasion, however I am no closer to solving the mystery! I have unplugged wires and moved them across the channels. I have tried holding the mic in hand. I have tried moving the cables away from other electrical equipment.

All of these 'solutions' have been effective at one stage, but the problem still persists. Any suggestions? I'd hate to have to send this microphone back! When it works, the audio quality is flawless! (To my ear! :D)

[EDIT] I should also mention that the buzz is still apparent when monitoring through the mixer and when not connected to the computer.
 
That sounds like mains hum from a ground loop.

A couple of things to play with.

The next time you hear the hum when monitoring off the mixer, disconnect the usb cable and see if it goes away.

If it does, reconnect the usb and, assuming you're using a laptop, unplug the power supply from the laptop and run off battery for a few minutes. Does that make the problem go away?

One thing to make sure off is that the mixer and the laptop are on the same electrical circuit. If they are and you still have a problem, try moving them to a different circuit, even it it's just with a long extension cord to someplace else.

Anyway, let us know how you get on with the plugging tests I suggested.

Bob
 
Ground loop? I take it then that this isn't a problem with the mixer or the mic?

Thanks for all the tips! FYI I'm using an iMac, so I can't unplug that :p Currently the microphone is working well with no hum or buzz. When the problem next persists, I will try moving the power supply to a different circuit!

[EDIT] I should also mention that the mixer runs off an AC power supply and is not powered via USB.
 
It depends. Definitely power related. If you look at a spectrogram you'll see peaks on multiples of 60Hz (or 50Hz PAL/Euro). Unplug the mic from the mixer and see if you still have the hum from the mixer. If it goes away, it's likely in the stuff on the mic end of the mixer. If it doesn't go away, it's something further down stream. I had an issue once with a USB cable, but I don't think it was that type of issue. But something to test if you've got a spare cable or two.
 
Hmmm. Thanks for the advice! One other thing I forgot to mention, is that when the buzz and hum is present, the Main Level LEDs are lit and stay lit at around -24 and -12 ... If I unplug the mic, the LEDs fade... Wouldn't that suggest a microphone fault? :confused:
 
Don't think that's mains think it's a bad cable or shorted internal - it's the annoying noise the guitarist makes when he unplugs his lead...
 
bruiser1964 said:
Don't think that's mains think it's a bad cable or shorted internal - it's the annoying noise the guitarist makes when he unplugs his lead...
Click to expand...

I've been thinking bad cable... It was only a £8 ($12) cable from an electronics store. Can't see why there would be an internal fault - both the mixer and mic are brand new! I'd hate to have to send them back :mad:
 
There's two settings switches on my mic. One is a limiter I believe, as it has 0dB and -10dB marking next to it... The other switch is mystery to me. There are two markings beneath the switch. One of a straight line and one of straight line with an angle at the beginning. Any ideas?:confused:
 
The -10dB is a pad switch. It lowers the output of the mic. Useful for gear that's designed for lower input levels. Or excessively loud sources that are just to hot. The other is a high pass filter. aka Bass roll off. Or whatever the terminology of the week is. If you have issues like yours it can help by reducing the low frequencies. < 80Hz, it varies from mic to mic. But you either need it or you don't, and it's not normally an IF condition, depending on the day of the week. If you're in excessively windy conditions for example, it comes in handy to lower the handling / wind noises. Which lets you push the gain harder on the other parts of the chain. You want to try to avoid using either of those IMO. i.e. Set to a flat line, and 0dB. Only use them if you have to. In your case the highpass might help, but it wont "fix" the problem.

I'd suspect the cable(s). Not that it is, but in terms of cheapest things to replace. Or things that you're more likely to borrow or have more than one of, it's a candidate.
 
Yeah, the mic cable is a first thing to try. If a whisker of cable is touching something it shouldn't in one of the connectors it could cause that. Second guess is a possible fault on the ground for the mains circuits in the house itself or on something plugged into the same ring main-this would be hard to check.

It's less likely it's a faulty mic or mixer--but still slightly possible.

A word on ground/earth faults: this is a fairly generic description of a fault that can have lots of different causes. The noise you posted sound like 50 cycle hum and the mains frequency in the UK is....50 cycles. What this tends to mean is that a tiny remnant of AC power is getting into your signal path and being treated as a 50 cycle sound. I say tiny because it's a low level sound and nothing is smoking!.

The trouble is, this can be caused by all sorts of things. I asked about your computer because it's quite common for laptops to be not very good with their power arrangements. It's quite possible for them to leak power down any copper wire including a USB cable. Similarly, Pin 1 in an XLR connector is often earthed to the chassis of the mixer and/or microphone so if any stray mains is going to earth, it can get into a badly made connector....and so on. As I say, there can be lots of causes and detective work, especially when the problem comes and goes, can be a pain.

Glad you like the sound you're getting when it's not humming though!

Bob
 
I'm pretty certain it's the cable. I've rearranged my desk so that the XLR cable is kept away from all other cables on my desk. I've got my mic and mixer a fair distance apart from each other as well, as when they were close together the problem seemed to occur more often. That was probably mere coincidence however. I will update if I find out anything else.:rolleyes:
 
I used to have this, try turning up the sound sources earlier up the chain (ie gain, main mix etc) before trying to pump it up in the computer.
 
Triazic said:
I used to have this, try turning up the sound sources earlier up the chain (ie gain, main mix etc) before trying to pump it up in the computer.
Click to expand...

This is partly good advice. Getting your gain structure right so you're not amplifying noise later is always a good idea. However, the OP's set up shouldn't have any electrical noise at all--so it would obviously be better to track down the fault and eliminate it at source.

Bob
 
Just a heads up for everyone, I've found that detaching and reattaching the XLR cable from the mic seems to resolve the issue. :confused: Puzzling...
 
It's not a problem you should have though....something, either your new mic or the cable is faulty. Really you need to find somebody who can lend you an alternate mic and/or cable and see if you can sort out where the problem is then take the bad bit of gear back to the shop.

Bob
 
Sounds like the connector has a faulty connection. Whether that's the connector for the mic, or the cable? Who knows. Or the cable is so cheap that it corrodes easily. Some folks make a habit of replugging the cable several times to clean the leads. Something about contamination there making the susceptibility to radio broadcasts higher.

Otherwise your gear doesn't sound very shielded. If putting more distance between devices helps reduce noise. i.e. cables (again). Although some devices lack shielding too. Not normally an issue in the middle of a corn field. But in a tall office building with every interference known to man, or near a broadcast tower, high power lines, and other things. It all adds up. But that's why we record at home. 3am-ish, the road traffic has ceased. It's cooled off and the A/C isn't cranking. Anyone who might have been doing laundry has finished doing it. The neighborhood dogs have lost their voice, and other pleasantries.
 
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