Qu16 With QSC k10.2 Noise

Qu Qu Troubleshooting
1

Hi everyone,

I am totally new to Allen & Heath. Two days ago I bought myself QU-16 and spent about 4hours youtubing and learning tutorials and finally I got simple system up to work. My setup is very simple.

QU16
QSC k10.2 Pair
Shure BLX4R with Beta 58A
Furman Power Conditioning M-8Lx
Monster Power Conditioning Pro-2500 (kinda old)
Samsung TV 3.5mm audio out to Line 15 and 16.

I ran into an issue with noise coming in into my QSC. It is not a 120hz ground loop issue more like 60hz sshhhhh and they are quite noticeable from 3-10ft away.

These are the steps I have done so far to isolate the issue.

Try 1: Only QU16 and QSC are using Furman and Monster (everything else are off)

Firmware are up to date. Electronic equipment within 10ft or more are off.

  1. I Make sure QU16 and QSC are plugged into Furman and Monster
  2. I make sure QU16 has only Main L&R out to the two QSC k10, nothing else, no mic, no sub, except ST3 in 3.5mm
  3. I use 3.5mm input into ST3in with my Ipad to play music from youtube
    Result: After the music kicked in for a few seconds, I muted or stop the music from the channel ST3, and I noticed the noise from both QSC k10 from at least 8 feet away.
  4. I unplugged both QSC k10 from Main L&R, and of course no noises. Plug them back in and noises again. I LEFT THE SYSTEM IDLE FOR ABOUT A FEW MINUTES, NO NOISES COMING OUT. Then again if I started the music and stop, noises again.
  5. I switch out with another XLR cable from QU16 to QSC and no change.

Try 2: I remove both Main L&R from QU16. Without using the QU16, I plug my 3.5mm directly into the QSC k10.2 and play the music and then stop the music, and no noises can be hear when stand front of the speakers (3ft)

Conclusion: I came into my conclusion that QU16 produced noises and I could be wrong, but I have exhausted my options and leaning toward return the unit for another one from Guitar Center. Any suggestions please feel free to add. I am looking forward to resolving the issue without return the product.

Thanks in advance.

2

Do you have the K10 set for mic or line input, it should be line?
(Each input has a line level input setting)

Do you get the noise with nothing connected to the mixer except the outputs
connected to the speakers?

Does the noise level change when you turn the master fader up and down?

Did you check that you do not have the tone / pink noise generator turned on?
(set up menu under the audio tab)

Do you get the same noise if you connect the speakers to one of the mix outputs?

Do you hear the noise in headphones plugged into the mixer?

Make sure you XLR cables do not have pin 1 tied to the outer shell of the connector, some of the import budget cables come wired that way.

I would describe a 60hz sound more like hummmmm.

Post a link to a clip of the audio or even a cell phone video of it.

” I LEFT THE SYSTEM IDLE FOR ABOUT A FEW MINUTES, NO NOISES COMING OUT”
That comment makes me think the K10 has a signal mute if it does not detect audio
input level after a few minutes.

Without a transformer isolation there’s 50 50 or better chance that when you connect part of a video system to a sound system that you will get hum, buzz or noise of some type.

3

Try getting a 3.5 to 1/4” Y cable and attach to st1 or st2. I believe I’ve read posts here of the usb connector introducing noise.

4
I’ve read posts here of the usb connector introducing noise.

It can/has but the latest firmware took care of most of that issue and I don’t think he is using the USB for anything at this point.

5

Hi Mike,

Do you have the K10 set for mic or line input, it should be line? YES - both inputs are LINE
(Each input has a line level input setting)

Do you get the noise with nothing connected to the mixer except the outputs
connected to the speakers? When the system is completely off for awhile and turn back on with k10s not much noises at all. After play music from itune for 5-10mins, at the beginning (i stopped the music to track the noise) the noise is comfortable later on the noise getting worse ( i can hear from 6 ft away). I unplugged the input 15 and 16 and their faders and Main fader all down, still the worse noise. Raise the Main fader to max…higher noise lvl output.

Does the noise level change when you turn the master fader up and down? So after Qu16 warmed up, I unplugged line 15,16 and their faders down. When I use Main fader up and down, the noise will increase and decrease as I use the fader.

Do you get the same noise if you connect the speakers to one of the mix outputs? Interesting questions, thanks for asking. I did this test before and here the result: Main L&R, Stereo Mix 10&9 have the same noise lvl. Stereo Mix 8,7, Mono 6 to 1 are very quite.

Do you hear the noise in headphones plugged into the mixer? Sorry, I do not yet have a headphone 1/4 to test this part.

Make sure you XLR cables do not have pin 1 tied to the outer shell of the connector, some of the import budget cables come wired that way. One set is Live Wire from Guitar Center, the other Set is Mogami GOLD.

I would describe a 60hz sound more like hummmmm. So this part is what confused me. If I move my ears near K10s, I hear hummm from the low part of k10. Pink or random Pink noise from the top part. But from the distance I would say, the PINK noise is much more dominion

Post a link to a clip of the audio or even a cell phone video of it. I will my best to make this part happened.

” I LEFT THE SYSTEM IDLE FOR ABOUT A FEW MINUTES, NO NOISES COMING OUT”
That comment makes me think the K10 has a signal mute if it does not detect audio
input level after a few minutes. You are absolutely correct. I contacted QSC tech support, they said if you have a DIRECT connection of Line, Mic, 3.5mm into the K10s and you hear no noise or hummm the K10s are working perfectly fine.

Without a transformer isolation there’s 50 50 or better chance that when you connect part of a video system to a sound system that you will get hum, buzz or noise of some type. Do you have a link to one of the product you recommanded…see if I can get them local or from Amazon.

Thank you so much

6

Try getting a 3.5 to 1/4” Y cable and attach to st1 or st2. I believe I’ve read posts here of the usb connector introducing noise. Mike is correct…I do not have any USB. I do have a 3.5mm Y to dual 1/4 into 15&16

7

Are you sure, that all channels except the one for the iPad are muted? Maybe there is a hidden signal source, which create the noise. Once I got an audio interface with a buildin DSP mixer for really little money because the owner complains in strange noise of the device. So, I gave the device a try and found out that all inputs are set to maximum gain and are all sent with full level to all outputs. Now I have a fine interface for small money. :wink: try to initialize the mixer, mute all inputs, returns and all the rest. Just use your iPad, or even better some WAV files (CD rips) on a thumb drive and play only them via an assigned channel. If you use the iPad, put the output level of the iPad to maximum and adjust the input gain of the mixer to approx. -10 to -6 dB. Raise the channel fader to 0 dB and adjust the main mix to a desired level.
I have, among other speakers, also two K10.2 and there is no noise issue with any of my mixing consoles. Set the level of your input you use to 0 dB, the others to off. Set the preset to default, as a first step, and the input sensitivity to line. Do not use any EQing of the K10.2.
Use some symmetrical microphone cables with XLR connectors to connect the QU16 to the K10.2.
And last but not least. Remove the power conditioners. Maybe they are not in a good shape anymore and are producing unwanted noise even if their task should be the elimination of power issues.
If you follow these steps you should not hear any noise.

8

Did you check that you do not have the tone / pink noise generator turned on?

With the master fader all the way down is the noise gone?

As MFK suggested mute all the inputs, don’t forget to mute the top layer that has the stereo inputs and the
FX returns, mute the FX returns as well.

Do a full mixer reset and then see what the noise is like with nothing except the speakers connected.

9

Here is a link to a DI box for the that would work to connect the TV.

Radial AV DI

If your working with a device that can provide audio output via USB you could connect
that directly to the mixers USB B IO and set up the input that way or use a USB DI box.
Here’s a USB DI that works well for a good price.

Peavey USB DI

My earlier comment on doing a full hard board reset is just to make sure all the board setting would be at default.
Do the reset and nothing else then bring up the master fader to see what the noise is like with no inputs connected to the mixer.

10

Hi Mike and others,

My earlier comment on doing a full hard board reset is just to make sure all the board setting would be at default.
Do the reset and nothing else then bring up the master fader to see what the noise is like with no inputs connected to the mixer. I tried this as you suggested, but no change…noise still coming out to Main LR after audio played (even after stop and unplugged ST3 or input 15 and 16).

After exhausted all my options and talked to a few friends of mine and with all your suggestions to get this to work. Unfortunately, I have finally decided with at least 95% confident that I have a bad unit. So I took it back to GC and exchange the unit for another Qu16.

The New QU16 works wonderfully.

I would like to end this thread with a result of a bad unit.

Thanks everyone.

11

Good to hear it is resolved and GC did a quick exchange for you.

The last few days you did pick up some good trouble shooting skills!