Last night my desk all of a suddenly started clipping in the mic imputs

With a mic plugged in, or with the input open? With the channel volume up or not?

1. Turn the main and monitor volumes all the way down (off). Plug a cd player into channel 9/10 and play a track of music of your liking. With the main/monitor volumes still off, adjust the gain on 9/10 until the clip light turns on, then back it down until the clip light just turns off. Put the channel volume at 12 o' clock.
2. With the music still playing, turn up the mains to the desired listening level first, and then adjust the graphic eq until the music sounds good in the room. Remember or mark the position of the volume control. Do not use the channel eq on 9/10 for music that has been mastered properly, leave the eq flat. Once this step is completed then you have now set the main eq.
3. Repeat the same for monitors. Turn off the main volume and then bring up the monitor main volume to the desired level first, then set eq. Now your monitor eq is set properly. Remember or mark the position of the monitor volume.
4. Set up microphone - plug a mic into channel 1 with volume all the way down. Speak or sing into the microphone and adjust the GAIN until you see the clip light, then back down a litttle on the gain. Put the monitor and main volumes back up to the mark from step 2. Now adjust the volume and monitor send on the mic channel to the desired loudness first before adjusting the mic channel eq. Use subtractive eq method to minimize distortion and feedback. ...i.e. if the mic is bassy then turn down the lows, do not ADD highs. If the mic needs bass, turn down the highs.

Which clip light on what and what mics are you using?
The small room settings are from 10 so just turn the know to the setting you require and press it, this should set it.

The stadard way of setting up mics is to set the channel gain so the channel clip light just blinks occasionally when you are making the maximum sound you can into the mic.

For effects repeat this process using the aux send FX for each channel you want fx on (turn the rest to 0) and doing a balancing act between these and the aux send fx master so you can only just get the FX clip light blinking occasionally.

Next set your gain/attenuators on the amp(s) so its clip warning can just trigger when you are giving it 0db when you are playing the loudest you ever will.

A mic fading away could be the battery dying (in which case try using phantom power) or if they're radio replace the batteries before each service. If they're wired dynamic mics then it is possible there's some protection circuit somewhere that's reacting to the constant clipping and backing off the amp.

Yes you can,you will need 2 run ,1\4 in 2 jack 1\4 in imput too the mic\line imput your chaing your signal so you will need too preset vol levels on the 120 too your desired max peak out put buy first putting you output slide too max on your mixer (running a signal from a cd player or other divice into mixer)then turn vol up 2 disered max loudness you want to run sound at then lower the vol using out put from main power slide on your mixer. Its called chaining your componets .better way of hooking up a band on a small system.ywc Rev bob dj 25yrs exp

If the mic is a low Z- mic, that might be the issue. Check the mic straight into the sound card of the mac and see if it works or if it is shorted. Is there a switchon the mic? it may be dirty.

These seem to be tempermental. I would look for radio frequency interference from nearby transmitter leaking into your guitar cable or mic cable that puts this on the ragged edge of feedback. DO NOT boost highs with the EQ... You can get supersonic feedback that you can't hear, but puts the amp into limiting. Any audio input can start the feedback. These amps are VERY hard to work on due to the packaging. A lot of people have smoked their units and then require repairing.

Some mics will require the trim gain to be full on. Check the mic gain by pressing the PFL for each channel and set trim to be below the clipping level with maximum vocal into the mic.

There are some low output mics that may be inadequte as far as output goes. Shure SM58 are industry standard mic... If you don't have one to try, borrow one to test with.

After that, the slider, EQ controls and the MAIN sloder has all the control.

Thiis amp has plenty of gain for mics. Make sure your mic has a good XLR to XLR cable (balanced) and connects to the XLR input connectors. If you have 1/4 inch jack cables that aren't TRS balanced on the mics, get rid of them and get XLR's.

Then push the PFL button down (LED will light red) for a single channel with a mic and adjust the trim (top knob for the channel) so that the level peaks without clipping on the main LED display when highest input to the mic is being generated. You should not get clipping then during operation.

After that you use the slider tio adjust the level for the mic. The MAIN slider should be at least up around -10 to zero during operation. If your main slider is way down, then you haven't balanced your channels properly. Do the same for each channel as the instructions for the mic above. If the gains of the other inputs are too high and the MAIN slider too low, this is what is causing your problem.

Typically the trims for mics like Shure 58 are about 3 o'clock.

High level guitars may have trims anywhere from 9 to 3 o'clock.

Ideally you will want your channel sliders to be between -10 and zero.

try this;

1.using different usb inputs on your pc desk top
2.update drivers on both your desk top and laptop
3.using a different usb cable

if it works fine on your friends computer most likely its not the mic

I would try unplugging some of the extras. All of that could have been causing your line voltage to sag too low for the mixer supply to operate properly.