Shot in the dark question about mixers

[BassYerbouti]

sorry to use this area to ask a dumb question but we have a gig tomorrow night and are using an unfamiliar mixer. plus we are fairly clueless when it comes to PA's

we used it 2 weeks ago and eventually got the thing working but along the way managed to deafen the pub with huge feedback during the setup. It's a Yamaha MG series mixer. 

the thing that freaked us out was that we had all the mic faders all the way down but we were still getting sound out of the speakers from them.  Sounds like we did made a rookie error.  Can anyone explain what we might have done wrong please?

regards,

Chris

[cheddatom]

you probably had the speakers plugged into a monitor or an effects send, and one (or more) of the mics sent to the related bus

[mybass]

Agreed with Cheddatom, I've seen that done before, awful racket as a powered monitor was plugged into the (rear) PA speaker output of the amp.

[pete.young]

Great mixers the MG Series and I find very easy to use, but I have one so am biased. Probably Aux bus weirdness as Cheddatom says.

Pete's rough guide to MX series mixers:. This doesn't include the digital effects, if you have any. Start with:

All channels switched off. All channel faders down. Group bus faders ( dark grey) down. Stereo (Master)  fader (helpfully coloured Red) down. All EQ's to 12 O clock. Pan r/l to 12 O clock. Compression to zero.

All 'pfl' buttons up. All 1-2 and 3-4' buttons up (if you have these). All 'ST' buttons up. All the aux channel sends to zero (the ones with blue tops). All Aux master volumes to zero.

Connect everything up. Power on mixer, amps, powered monitors in that order.

For each channel:

Turn on the channel and press down the pfl button for that channel. Get someone to speak or play and adjust the 'gain' control until the output in the VU metres is occasionally reaching 0, in green. Put the pfl button back in the 'up' position and turn the channel off.

Lather, rinse, repeat, for all the channels you're using.

Set the monitor/phones switch to 'Stereo' (up) and turn on 'On' and 'ST' for the channels you're using. Bring up the faders on individual channels and get a rough balance on the headphones. When you're ready, bring up the Stereo fader gently until you get FOH.

Optionally, increase compression but don't overdo it. If you want to adjust EQ, try and cut rather than boost. (ie cut mid and bass to boost treble)

If you're using separate monitors, connect them to one of the 'Aux' inputs on the back of the desk (not the 'Monitor' sockets on the top of the desk next to the headphone jack). Usually you want Aux1. If there is a pre/post switch set it to pre. Turn up the Aux Send master for the Aux you're using to somewhere between 12.00 and 3.00 and then turn up the individual channels Aux Send to get a monitor mix.

Hope this helps, good luck and have a great gig. If all else fails, read this! https://partydj.be/PDF-files/Handleidingen/Sound/Yamaha/yamaha-mg166cx-manual.pdf

[BassYerbouti]

Guys, and especially Pete, thank you very much for this information. We've definitely been using the 'Monitor' sockets on the top of the desk to run to another power amp that powers the one wedge we use for the singer. So wonder if that was the problem, We will try your excellent and clear instructions and report back.

Thanks once again,

regards, Chris

[pete.young]

That could definitely do it - if you had any pfl buttons down (stands for pre-fade listen) it takes the signal upstream of the EQ and faders and routes it through to the headphones / monitor socket. The monitor sockets on the top are intended for when you're using the mixer in a recording control room and want your playback through studio monitors. 

Hope it helps, when I started out I knew nothing and people here helped me a lot, so what goes around comes around.

[atsampson]

... and if you don't have any PFL buttons down, then the monitor output mirrors the main output (or a group output, on the bigger MGs). So definitely don't use it for monitor wedges! Use one of the aux sends instead.

[EBS_freak]

Also, if using active speakers with a mic/line switch, make sure it is switched appropriately.

With regard to the green lights on a channel, memember that a mixer is summing all the channels... so that if all your channels are registering near 0, by the time they are summed at the LR, they could send the main output into clipping... so be careful where your LR is placed. In other words, don't push that LR too hard.

[bazzbass]

If you're getting good money, hiring a good sound engineer is the best way to sweeten your FOH sound

[Phil Starr]

I'd avoid any compression on the MG unless you really know what you are doing. They really increase the likelihood of getting feedback, especially if they are used on the vocal mics. I only use compression on the kick drum. Turn them all right down to zero before you start.

[Dan Dare]

Comments from others above are very helpful - make sure your outputs are connected correctly, using pfl (if the mixer has one) to set initial levels, etc. Assuming that is the case, it's important to set the gain structure correctly. You have three stages of gain in a mixer - the input gain, the channel fader and the output faders. Each stage feeds through to the next and they must be balanced to each other and not over driven. A quick and easy way to get started is to begin with all turned fully down. Then set the main outputs at around -5db (keep the power amps feeding the main system and the monitors off at this stage) and the channel faders at 0db. Whilst someone sings into each mic/plays each instrument, slowly raise the input gain until the signal lights show at around 0db, or maybe -+3db on peaks (allow for the fact that people sing/play more gently when sound-checking than they do when the gig is underway) and adjust the eq to suit. It helps to do this on headphones. Then set your monitor levels. If you are using monitors, roll the bass end off quite hard - that is a frequent cause of feedback (and you don't need heavy bass in monitors - you can hear plenty of it from the room normally). Once you are happy, raise the gain on the power amps feeding the main PA until the overall level is as desired. That should leave plenty of headroom and allow you to increase the output faders if you wish to raise the overall level during the gig, or individual channel faders if you want to hear more of a particular singer or instrument, without running into feedback issues. Hope this helps.

Edited December 23, 2017 by Dan Dare

[BassYerbouti]

Wow- so much helpful information guys - thank you . We followed Pete's instructions to the letter and got a good set-up first time. We are starting to know what we are doing which takes the stress out of it and let us concentrate on playing. Would be great to have a sound engineer but we are getting paid peanuts. Our plan is use proceeds from recent gigs to slowly build up our own PA - starting with a 12 channel version of the larger Yahama we've been borrowing. That way we can set it up and label it for our line-up. 

Thanks once again and happy Christmas to everyone.

regards,

Chris