Mixer Noise

B

Big Mike B

New member
I bought an ALTO ZMX 244 FX USB mixer and I have a problem. I'm getting a constant stream of noise, even with all the faders (channel, subgroup and master) down and all mic preamps at 0dB. The noise is only heard through my DAW (REAPER) but not through the headphones. I'm wondering whether it's some post-master fader issue.
Can anyone shed some light on the subject? I got a sample of the noise in case it's characteristic to anything common.
[MP3]View attachment untitled(1).mp3[/MP3]
View attachment untitled(1).mp3

I amplified it by 24dB but usually the noise comes in at ~-36dB.
 
Last edited:
It made a lot of sense initially, but I realised that my laptop isn't actually earthed. The noise, as described, was a high pitch whining, but since the laptop isn't earthed, the ground loop cannot be completed. Any other ideas?
 
Damn. That's annoying.
Are you connected to anything else that's earthed? Printer, for example?

Hello from up the road, btw. I'm near Belfast.
 
Nope, the only thing I had connected to the laptop was the mixer, charger and headphones. I know that this isn't a feedback issue because when I disconnected the microphone, the noise was still there.
Nice to hear that there are actually people with brains in Northern Ireland. :P
 
Big Mike B said:
Nice to hear that there are actually people with brains in Northern Ireland. :P
Click to expand...

Hmm, that remains to be seen. :p
I hope someone else has experience and can help; I'm kinda stuck.

Out of interest, is there any change when you remove the laptop charger from the equation?
I know it's not a path to mains earth, but it has been known to help.
 
Yep! Cheap A-to-D converters built into mixers with USB. My Mackie ProFX12USB is the same way. I had read comments about it AFTER buying it, but had never heard the noise myself until I turned the USB knob up past 11 o'clock one day - because the signal sent from my computer to the mixer was low in volume, I had already slid the main sliders up, my monitors were on full volume, and I turned the knob and got that high-pitched noise on playback. Some experimentation showed the same thing happening when sending the signal to the computer.

I can't tell from the picture I found if the Alto has a USB volume knob or not.
 
I am guessing the laptop is Win 7?

If so the noise is due I am sure to the usb sound channel having far too much gain.

If it has worked the attachment should show the spectrum of the noise with the characteristic spikes. You cannot eliminate these spikes but you can push them down to -75dBFS or so where they won't be heard above ambient noise.

Go into the sound menu and find "usb microphone" or similar. Find "Levels" then crank it down from 100% to around 5% or even less.

Agreed the problem is caused by cheap ass'ed converters and drivers but also because Win 7(w8?) defaults generic usb audio device to mic gains. The final solution is of course a proper AI with decent drivers and 24 bit operation.

Dave.
 

Attachments

  • Spectrum w7noise.png
    Spectrum w7noise.png
    6.7 KB · Views: 30
Big Mike B said:
I have headphones volume, control room volume and master fader. None of these affect the noise.
Click to expand...

Nope, USB volume, which obviously that mixer does not have. You can try to use a parametric EQ in your DAW to find and reduce gain at the bad frequency, but other than that, you're stuck and need to use a proper audio interface. Sorry. Mixers are for mixing sounds (live use) AIs are for converting sounds to digital for recording.
 
The first time I encountered this problem was not with a "crap" mixer at all but with my A&H ZED10!

I normally run the mixer into a 2496 PCI card but decided to try the usb system out one day. Plugged into my P4 "PCWorld 3G special" it was fine but when I tried it on my W7/64 tower PC I got a 5kHz whine at about, iirc, -50dBFS and quite obvious on clean voice or acoustic guitar recordings.

I hastily posted off audio clips and graphs to messsrs A&H and within a day they came back with the solution I mention above.

Now I have had 4 other usb AIs: Behringer BCA2000 (wish they still made that but properly!) Tascams 122 and 144, Fast track pro and the present incumbent, an NI KA6. None of those gave this noise issue on XP and the Fast track and the 122/144 did not on W7. The KA6 is of course perfection personified! But! You would expect a cheapo Behringer UCA202 interface to suffer? Not a bit of it and for 20 quid or so these are very useful wee boxes, fine for example for ripping tapes to PC.

Beats the H out of me!

Dave.
 
NOISE-EQ.jpg
That's the EQ curve I get. Amped it by +36dB so that you could see what I'm getting. This seems to be much lower than what I was getting when I first posted this thread, but it's still audible and I have nothing connected to the mixer (no mics, all faders at -∞, EQ and FX all off). I don't hear this noise on headphones.
I know that the noise isn't a constant set of frequencies, but do you think I could take a sample and invert it out of the recording to get most of it out?
Another thing I was thinking of doing is connecting the PHONES OUT to my AI (Line 6 UX2) and see if that helps to get clear recordings.
 
Umm, no one has asked, so ...
What are you recording? Use the UX2 as your audio interface, forget the mixer. Or if you really like the mixer's preamps, take the lineout signal from the mixer to your UX2 (not the headphone output).

The frequency graph shows the spikes at 1K, 2K, 3K and up, you could try inverting the recorded 'noise' and adding it to the track and see if it works. It's coming from the USB part of the mixer, so it doesn't matter if there is no input signal.
 
I was initially recording acoustic guitar, but in a few months I'll be recording drums, and my AI alone won't be able to handle that, so that's why I need the mixer. Anyway, I guess we have found a workaround for my problem so I guess this thread is done unless someone has some other ideas. Thanks a lot guys!
 
You must log in or register to reply here.
Back
Top