Volume output level is low on all channel.

Question edited for clarity and the real name of the model, plus all the typos.

Send it back and claim a 3 year warranty repair. It may be dirty controls, but could also be failed internal components like blown capacitors.

https://www.behringer.com/service/service-warranty.html?modelCode=P0AEB

https://www.google.com/search?q=Behringer+EuroLive+B115D

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1. Connect the output of the Yamaha MW12CX mixer to the input of the Stagepas 500 using a standard 1/4" instrument cable or an XLR cable. Connect the output of the mixer to the "LINE IN" or "MIC/LINE IN" jacks of the Stagepas 500, depending on what type of output signal you're sending from the mixer.
2. Set the levels on the mixer and the Stagepas 500. Turn down the master volume on the Stagepas 500 and set the individual channel levels to zero. On the Yamaha MW12CX mixer, set the faders for channels 1 and 2 to the unity gain position (usually around 0 dB).
3. Set the input mode on the Stagepas 500 to "LINE" or "MIC/LINE" for channels 1 and 2. This will ensure that the Stagepas 500 is receiving the correct input signal.
4. Adjust the levels on the mixer and the Stagepas 500. Slowly turn up the volume on the Stagepas 500 while monitoring the levels on the mixer. Make sure the levels are not too high and that there is no clipping or distortion.
5. Once you have the levels set correctly, you should be able to hear the sound coming through the Stagepas 500. Adjust the EQ and other settings on the Yamaha MW12CX mixer as needed to get the sound you want.

Note: The Yamaha Stagepas 500 has two more channels available, channels 3 and 4, which can also be used for additional inputs from the Yamaha MW12CX mixer or other sources.

If you are experiencing low volume output from your Icon IC 41 Pro speaker/microphone, there could be a few possible causes. Here are a few things you can check:

1. Check the volume settings: Make sure that the volume on your speaker/microphone is set to the maximum level and that the volume on any connected devices (such as a phone or computer) is also set to the maximum level.
2. Check the audio source: Make sure that the audio source (such as a phone or computer) is not set to a low volume level.
3. Check the cables: Make sure that all cables are properly connected and that there are no loose or damaged connections.
4. Check the battery: Make sure that the battery of the speaker/microphone is charged or replace the batteries if necessary.
5. Check the speaker: Make sure that the speaker of the speaker/microphone is not damaged or blown. A damaged speaker can cause a low volume output.
6. Check the microphone: Make sure that the microphone is not covered or obstructed. A covered microphone can cause low volume output.

If none of these steps resolve the issue, I would recommend contacting the manufacturer's customer support for further assistance. They may be able to provide additional troubleshooting steps or may recommend a qualified technician to repair the speaker/microphone.
It's worth noting that if the speaker/microphone is under warranty, you should contact the manufacturer to have it repaired/replaced.

Realize that the number on the volume control is only relative... it means nothing regarding what the amp can produce. With a high level output guitar you can easily drive the amp into distortion at very low volume control level settings... what counts is the actual output sound volume and specifically the voltage output going to the speaker. Once the amp reaches saturation, any further input just pushes it into distortion or "flat topping".
An oscilloscope on the output will quickly show when amp starts to flat top.

Directv low volume problem.
One sure way to eliminate Directv's low volume and any other volume problems in general is by installing a stereo compressor between your Directv receivers audio outputs and your TV's audio inputs. (Simply plug the compressor's outputs into TV and your receiver outputs into the compressor's inputs). By correctly setting the controls on the compressor, you won't loose the dynamic program content. Not only will it raise the volume level to where you want it be, it will also prevent it from exceeding any set level you chose, actually limiting how loud any sound can be. These settings are fully adjustable. In other words when you switch from Directv back to a dvd or any source, no more sound blasting, you can set levels to be the same now since you have raised then adjusted Directv's level to normal. Plus a compressor will raise those low hard to hear audio sections often found in movies. This is the reason we used them all the time in the recording industry. Another benefit is it levels all channels on Directv. The result, channels are now the same volume. This is what I'm doing to end the problem. Hope this helps someone. J Pynckel

It sounds to me that all you are getting is the pre-amp stage of the amp and nothing from the power amp stage. As it is on both channels then it is something that is common to both. This could be something to do with the power supply of the power stage. Or whatever is on the heatsink. It could be that the amp uses a single audio amp IC for both channels. If it does my bet is that it's gone. If it uses two sets of semiconductors for the right & left channel it would be highly unlikely that both channels have gone, but not impossible.

if you are using a digital converter along with a standard tv , you have one volume level low making the unbalance sound a humming sound, if it is directlly into your tv, check your settings on your tv bass, trebile, by the sound of it you probably have a digital converter , if this is so, raise the volume of your TV to mid point that raise /lower your volume on the converter and it should be fine, also make sure your ouput channel is not the same as your broadcast channel in your area, example,,if your area uses channel 3 for broadcast, set your rf output to chann 4 , and vice versa.

Well, some TV stations do broadcast at different volume levels. This is very noticeable when watching a TV show and the volume seems normal and then when a commercial comes on, the volume is very loud. They do this to get you to pay attention to the commercial. Another problem might be that you are adjusting volume from both your TV and your cable box. What you should do is make sure your cable box is set to "FIXED VOLUME" and then just adjust your TV volume. Fixed volume will have the cable box output only one volume level, letting the TV do the adjustment. Just go through your cable box setting and look in the audio settings. Hope This helps...

I been replied you in chat thread, please check and feel free to ask any question.

Channel level output can be adjusted in the menu if you have the remote. Set the rear channel level volume higher and the fronts lower if need be, and then turn up the volume. Enjoy!