Problems Qu combined with Shure GLX-D

[RuudParticipant]

In combination with my A&H QU-24 I am using 4 Shure GLX-D/beta 58A (digital wireless mics). To my opinion this should be a nice combination! But……!

Sometimes, especially at higher volumes, a get a ringing tone at a frequency around 11 kHz. It sounds like feedback.
As this does not occur with an analog (Soundcraft) mixer, it must be the combination. I don’t have the opportunity to test on another digital mixer.
One of the issues could be the difference in sampling frequencies: QU-24 is 48 kHz and the Shure GLX-D uses 44,1 kHz. If that is the problem I have to assume that the LP-filtering of the Shure GLX-D receiver is not effective enough.
But I did not yet find any combination where the differences in frequencies rsult in a ringing tone of approx. 11 kHz.
Or could it be that overloading of the mic result in other frequencies than only 44,1kHz (as it appears only at higher levels).

Anyone have the same experience or have any suggestions?

Thanks

Ruud Franken
Noise To Sound
Assen – Netherlands

[AndreasModerator]

11kHz can’t be a feedback issue. That would require an overall latency below 0.1mSec, that’s way below you get from a digital mixer (and need get the mic in contact with the membrane of the tweeter).
What’s the connection between the receiver and your mixer? I’d suspect some kind of grounding issue or a nasty switching power supply.

[RuudParticipant]

Hello Andreas,
Thanks for your reaction.
The connection between the GLXD receivers and the mixer are simply XLR-XLR signal cables. The Shure receivers have external power connectors. I tried with or without ground lift. Which did not result in any solution.
I’m also convinced that it is not a feedback matter. After a lot of experiments (it does not occur at predictable moments!) I think it has something to do with interferences between some frequencies, which have nothing tot do with the audio-signal. Such as (digital) sampling frequencies or carrying frequencies. But until now I can’t find the match that result in approx. 11kHz.

[airickessParticipant]

Make sure that there isn’t any Wi-Fi interfering with the GLX-D. They do run in the 2.4gHz range.

[Author]

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