Sensor that measures line level audio voltage - need help

Hello, first time poster here. I’ve now spent a scary amount of time combing the internet for information and I’m out of ideas, I need some advice.

I own a music recording studio. I’m looking to implement some novel ideas to improve the ergonomics of the space. One such project is to measure the audio line level voltage being sent to my speakers in real time and then allow Home Assistant to create automations based on those data.

Audio line level voltage is in the range of 0 - 2V AC. (Line level - Wikipedia) All of the products and solutions I’ve found are suited for either mains (120V AC) or something like 12-24V.

There are some interesting solutions proposed using ESPHome and small DIY circuit board projects, but it’s been years since I’ve done anything on that level - it seems like a serious investment of time for someone of my limited experience.

I’d love to find an “off the shelf” solution to monitor the audio voltage - something that I could pair with zigbee or z-wave, attach a project box to the inside of my equipment rack, screw in some wires, and be on my way.

If I can’t find that, and I need to go to the DIY/ESPHome/circuit board route, perhaps someone can give me some quick-start advice? I’m a total novice to this side of things and 99% of the information out there is comparatively quite advanced.

Sorry for the long-ish post and thanks for reading.

Are you talking about a constant-voltage speaker system where the power level of each speaker is determined by a tap on the transformer?

That’s kind of low-fi used in grocery store MUZAK systems/ (The ones I installed certainly were). Why would you use it in a recording studio?

No. I am talking about line level audio signals

Then I am confused. Line level, as a line input to a preamp is usually 1V P-P or a bit less. Are you using amplified speakers like Klipsch?

Even then, I don’t see the benefit of measuring that voltage. Line-level inputs are high-impedance. Meaning that there is very little power in the signal. The load of a meter or an AC sensor on an ESP analog input would adversely affect the voltage, making the measurement rather useless.

So, yes, to answer your question, you could use a full-wave rectifier to feed a DC level voltage into the ADC input of an ESP device. You would have to calibrate the input voltage to the actual AC voltage.

But, again, why? Or am I completely misunderstanding your question?

Thanks for brainstorming with me. I want to detect when audio is playing, and use that as a trigger for Home Assistant to turn on power to the speakers.

Another way to accomplish this would be totally in hardware, with a box like this:

So you want a dead air sensor. This is your off the shelf solution. Just connect the relay contacts to a Zigbee switch. Then in your Home Assistant automation, trigger on the state of the switch.

Ahh, interesting, so how will I define the threshold at which the zigbee switch detects it to be “on” ?