I have a couple (10 or so) microphone XLR inputs that goes into my analog mixer Allen & Heath PA20. The problem is that the channel inputs don't have a signal LED that lights up when someone speaks. So I have to rely on a stage hand to communicate to me, the currently used microphone or I have to individually check the PFL levels of the channel.

I am looking for a cheapest way to fix the issue. Either a device that I can use as a bridge between my microphones and the mixer which tells me the currently spoken into microphone.

Or a custom solution like attaching a Raspberry Pi in between and using a simple algorithm to figure out the active microphone (maybe getting the max level from all inputs and then using thresholding on the max level)

  • 1
    The simplest fix is to get a mixer with meters on each channel.
    – Rory Alsop
    Apr 6, 2022 at 10:57
  • I haven't owned an A&H in 40 years, but that one had an optional meter bridge… which I bought. It's either that or watch the stage constantly, so you know who's talking [easier with a band you've worked with before than a muttering bunch of lecturers, admittedly]
    – Tetsujin
    Apr 6, 2022 at 17:37
  • Have you a view over the speakers ? Colored rings or other visual clues can help to identify which mic is in use.
    – audionuma
    Apr 6, 2022 at 20:06
  • Really the simplest fix is to label each channel with the name of the cast member, then learn the show, who is acting in it, and what their voices sound like. Then, when you hear one of them speak, you will know which channel they are activating. Sure, it would be easier to get a mixer with a meter bridge or individual meters on each channel, but unless you can do that, you have limited further options.
    – Mark
    Apr 7, 2022 at 13:12
  • @audionuma, I don't have a clear view. I have a small TV, but by the time they change the camera from the previous speaker to the new one, it's too late. Apr 8, 2022 at 5:46

1 Answer 1


The most common solution to this issue is to use a Dugan Auto-mixer. This is either a standalone piece of hardware or a software feature built into some of the more modern digital mixers, for instance the Yamaha CL or QL series mixers.

Auto-mixers will automatically detect active mics and divert mix focus to those mics whilst automatically fading down unused mics in order to maintain the lowest possible noise-floor.

  • For auto-mix to work properly, one need to have proper gain settings on each contributing mic. That might be a challenge when the same mic is used by various speaker during the same gig.
    – audionuma
    Apr 9, 2022 at 5:32
  • Agree - however I am reading this as a panel show, with different guests each time the show is run.
    – Mark
    Apr 9, 2022 at 5:37

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