Ambient noise from mixer. (Thoughts?)

[hellfire45]

I attached a small sample file to this email.

I do a radio show and I noticed that some noise comes from just our mixer. This audio file is a recording from a 4 channel behringer mixer with ALL inputs unplugged using Audio Audition for recording. So it is literally just the sounds from the mixer going into audition.

You'll hear a little hissing noise. What is causing this problem and how do I resolve it? Is there a setting on the mixer or on Audition I can adjust or maybe I need a new mixer/software program?

Thanks you very much!

[turk690]

Adobe Audition will be installed in a computer, whose audio circuits may or may not be producing this noise. To verify, what I'd do first is unplug anything from the sound card inputs, then record segments with the computer sound card mixer program recording level control set at different levels, including both ∞ and 0dB, with a few points in between like -3dB and -20dB.
Audio equipment like mixers have very sensitive inputs who, despite being balanced, may still pick noise if nothing is physically plugged into them (plugging in a low-z mic "shorts" them out and noise pickup reduced). I'd try plugging in a mic (powered condenser, so can be switched off but mic internal transformer secondary is still plugged, so OK for our purpose) or a 600Ω patch to see if anything changes.
Lastly, ground loops can and will always find a way to introduce themselves in audio equipment. Though the most common evidence for ground loops is nasty 60Hz hum, in some cases it is a harmonic of the switching supply frequency (I bet this behringer has an internal switch mode supply, as is the computer). I'd first electrically connect the Audition computer chassis to the Behringer chassis, as well as use duly grounded AC mains connectors for both, plugged into the same CO.

[hellfire45]

Adobe Audition will be installed in a computer, whose audio circuits may or may not be producing this noise. To verify, what I'd do first is unplug anything from the sound card inputs, then record segments with the computer sound card mixer program recording level control set at different levels, including both ∞ and 0dB, with a few points in between like -3dB and -20dB.
Audio equipment like mixers have very sensitive inputs who, despite being balanced, may still pick noise if nothing is physically plugged into them (plugging in a low-z mic "shorts" them out and noise pickup reduced). I'd try plugging in a mic (powered condenser, so can be switched off but mic internal transformer secondary is still plugged, so OK for our purpose) or a 600Ω patch to see if anything changes.
Lastly, ground loops can and will always find a way to introduce themselves in audio equipment. Though the most common evidence for ground loops is nasty 60Hz hum, in some cases it is a harmonic of the switching supply frequency (I bet this behringer has an internal switch mode supply, as is the computer). I'd first electrically connect the Audition computer chassis to the Behringer chassis, as well as use duly grounded AC mains connectors for both, plugged into the same CO.

Sorry I should have said that I am using a laptop computer for this. I'm not really sure if I'll be able to open the laptop up and mess with the sound card. Also, I'm not sure I can do the final suggestion. As for the second suggestion, I literally unplugged all the inputs. There are no mics or cables plugged into the mixer's inputs.

[turk690]

Sorry I should have said that I am using a laptop computer for this. I'm not really sure if I'll be able to open the laptop up and mess with the sound card. Also, I'm not sure I can do the final suggestion. As for the second suggestion, I literally unplugged all the inputs. There are no mics or cables plugged into the mixer's inputs.

Even with the a desktop PC sporting a recent model main board with built-in a built-in sound card, audio can be a precarious venture, noise-wise. So many things conspire to produce noise of all sorts: the power supply, the processor, all other electronics introduce their bit into the mix. A laptop compounds the problem even further by confining all these components into a small space, upping the ante. Laptop audio can only range from so-so to the downright wretched; serious people who want to record stuff will never do so with any laptop's audio capability, which is only about as good for listening to downloaded horribly compressed itunes crap, but that's another storee.
The audio file you have uploaded is noise that varies from -50dB to -45dB. That's a fairly high noise floor (in today's world where we want and need it to be down to -100dB, even lower), but is about what I would expect from a laptop. I suggested completely disconnecting the mixer from the laptop audio line inputs and recording to see if the noise is still there (I bet it will be, a bit higher or lower); I don't think there is a problem with the mixer.
For serious recording with out these noise problems and much greater flexibility, I suggest going by stand-alone digital recorder devices. There are any number of these out there with killer specifications and do not cost an arm and a leg. They record to an SD card, after which you can immediately plonk into a card reader and read the pristine *.WAV file from. I use a Zoom H2n for the purpose; for multi-track I use Zoom R16. Never looked back.

[betwixt]

The noise from an open input may be higher than a shorted input, it depends on he internal circuitry of the mixer itself. No promises but try plugging in a shorted audio plug to inputs you are NOT using and see it it makes a difference. The only other option is a lower noise mixer. All amplifiers, including those inside mixers, produce a small amount of noise and it's impossible to remove it completely but some are better than others.

Brian.

[turk690]

The noise from an open input may be higher than a shorted input, it depends on he internal circuitry of the mixer itself...

That's what I said in my first post:

Audio equipment like mixers have very sensitive inputs who, despite being balanced, may still pick noise if nothing is physically plugged into them (plugging in a low-z mic "shorts" them out and noise pickup reduced). I'd try plugging in a mic ...

But as I said, I'd leave that alone. It's the laptop audio IMHO, and this is a price to pay for using it for this purpose.

[betwixt]

My apologies for the duplication. I too would say the laptop is the culprit, they are rarely if ever designed for critical audio applications.
Does the noise level change when the volume set by laptop mixer software is adjusted?
I assume you are using a 'line-in" socket on the laptop rather than a "mic-in".

Brian.

[hellfire45]

My apologies for the duplication. I too would say the laptop is the culprit, they are rarely if ever designed for critical audio applications.
Does the noise level change when the volume set by laptop mixer software is adjusted?
I assume you are using a 'line-in" socket on the laptop rather than a "mic-in".

Brian.

Unfortunately, we don't have a PC to test it with. We have 4 laptops (1 IBUYPOWER, 2 macbooks, and a Lenovo) and 1 "all-in-one" PC where it's all built into the screen.

So to summarize in a manner that a lamen will understand, the electronics inside the laptop may be causing some interference in the recording process. It's magnetism and electronics so its a tricky issue. Using a PC instead may work better and resolve the issue.

[jagabo]

Use a quality external USB audio recording device. That will completely bypass the laptop's audio section.

[hellfire45]

Use a quality external USB audio recording device. That will completely bypass the laptop's audio section.

We have 3 mics hooked up. It's not possible to hook them all up to the laptop.


I have 3 XLR mics plugged into the mixer in channels 1-3. They are all pretty nice, pencil condensors. Cost around $100 each. I have the mixer plugged into the laptops USB. That is how I have been doing it.

[turk690]

Use a quality external USB audio recording device. That will completely bypass the laptop's audio section.

We have 3 mics hooked up. It's not possible to hook them all up to the laptop.

I have 3 XLR mics plugged into the mixer in channels 1-3. They are all pretty nice, pencil condensors. Cost around $100 each. I have the mixer plugged into the laptops USB. That is how I have been doing it.

You are not getting this. You may carry on using the mics as plugged into the mixer. The purpose of using USB audio devices is to get away from the substandard laptop audio; better versions of these devices have line-in, and this is where you plug the mixer's tape out or rec out. The latter connections are standard on any audio console mixer, provided as part of a tape loop, and usually sport RCA jacks. You get an RCA-male to 3.5mm male phone cable (as USB audio devices mostly have 3.5mm input jacks). Plugging a USB audio device into a computer may require device drivers, which should come on a CD in the box. If properly installed and tweaked, Adobe Audition will see the USB audio device and its order of significance can be changed in edit>audio hardware setup.
Better quality USB audio devices from Creative and M-Audio have excellent noise specs, etc. But they still require a laptop or desktop USB port to operate. They may cost as much as or more than a stand-alone audio recorder, which is really the professional way to go about it. As I've said, these devices are extremely flexible, and they record to SDHC cards. After recording is finished, it's a simple matter of taking out the SD card, inserting it in the laptop reader, transferring the *.wav files and edit away with Audition or not. Some, like the Zoom H4n, even have XLR inputs which present the option of directly accepting, for example, the monitor XLR outputs of the mixer. This makes mixer and mic placement non-critical because the recorder can be some distance away due to the use of XLR cables. IIWY, I'd step away from my comfort zone, forget the wretched laptop for a few moments, and just get a recorder already. You are doing a radio show and your listeners deserve better than dinky laptop audio.

[Cornucopia]

I concur.

Scott