Output Hiss – QU-16

[Incandescence]

I’ve recently taken delivery of a QU-16 Chrome as my first digital mixer and I’ve got it set up at home to learn as much about it as I can. It seems to have a very noticeable hiss and I just want to see what anyone else thinks about it before I declare it faulty.

I’m using a Bose S1 powered speaker, in battery mode, with the bluetooth turned off, and with both other gains turned to 0. The channel I’m using is set to halfway.

I’ve got nothing connected to any inputs on the QU-16 right now, and I’ve got all the input channels (1-16) muted. I also have the L/R channel muted too.

When I connect the desk to the speaker via a balanced XLR cable, I get a loud static-type hiss from the speaker. Disconnecting the cable stops the hiss.

I’ve tried a 20M cable, a 10M cable and a 0.5M cable, just in case it was a faulty one, but I get the same static hiss each time, and it goes away when I pull the cable from the desk.

Any suggestions would be useful – especially as I try and get used to this desk.

I’ve also tried connecting to Mix 1, Mix 2, etc and get the same hiss no matter which output I use.

Could it be my mains supply, do you think (Mixer is on a fully earthed supply)? Or is it more likely a fault on the desk itself. Or is it something I’ve stupidly missed?

[Incandescence]

Meant to say – Unmuting the L/R channel makes no difference to the hiss volume.

[Giga]

Things to check:
* tone generator
* is the hiss also present in the headphone out
* try another outlet (incl the Bose)
* can you see the signal on the meters

Good luck !

Giga

[Rafael A&H]

Hello @Incandescence,

I would recommend you try a different pair of speakers to disregard any possibility of the noise coming from the speaker side.
Regarding the suggestions from Giga just above, I would also recommend performing a Hard Reset of the mixer to make sure all settings are back to fabric state and disregard any possibility of having a tone generator active or any other setting that could cause this or any other potential issue.
Steps for Hard Reset can be found on page 84 of the user guide: https://www.allen-heath.com/media/Qu-Mixer-Reference-Guide-AP9372_10.pdf

If after this you still encounter the same behaviour, please submit a ticket with our support centre at: support@allen-heath.com

Thank you!
Rafael

[Incandescence]

@Giga
Tone Generator is off.
Hiss NOT present in headphones unless I turn them all the way to Max volume which is normal
Outlets changed around the house & workshop to test – no difference
NO signal present on any meters either “real LED” or on the touch screen Levels or RTA pages

@Rafael A&H
I’ve just hard-reset the mixer, which made no difference.
I’d also tried using a larger pair of speakers with a separate amplifier and ground-lifted the amp in case. The result is the same in all cases.

Just to be sure, I’ve now unplugged the QU-16 and grabbed my old Behringer analogue to plug in and test. It’s definitely not the cables or speaker – the hiss is coming from the QU-16.
I’ve put a (bad quality – sorry) video of the issue online so you can hear the difference between plugged and unplugged:
YouTube Video Here

[Mike C]

Maybe check that your xlr cables do not have pin 1 jumpered to the shell of the connector. I have ran into strange noise issues and have found that the XLR cable
had pin 1 tied to the outer shell of the connector, easy to check by opening up the connector.

Some equipment that will cause an issue others not so much.

[Rafael A&H]

Hello @incandescence,

If this is a hardware failure it will require service of the unit.
Please submit a ticket with our support centre to follow up and advise how to proceed, at: support@allen-heath.com

Thank you,
Rafael

[Incandescence]

Thanks everyone – ticket submitted to A&H to investigate and get it fixed/replaced.

Great forums, by the way – I’ll certainly be hanging around to learn and help where I can.

[Author]

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