Except for Mackie, which are different, you set up a modern mixer with a clip light above the gain control (ie at the top of the row of knobs for the channel) by turning up the gain control (with the person singing or playing as loud as ever they are going to do) until the clip light just comes on. On most mixers in theory you now have 3db before actual clipping, but everyone goes louder in the heat of the gig so turn it down just a bit again. I can't see the channel clip lights on the picture of your amp but I'm sure there must be some there. Don't the instructions say anything? If there isn't one turn up until you hear some distortion (you may need to use headphones for this) and then turn it down until it sounds a readily discernible amount quieter - that's about 3 Db. Now turn it down the same amount again. You now have 6 Db of headroom before input clipping.

Clipping point can only be found with a meter if the meter is a peak meter, and most are power meters. On a typical meter you set the maximum expected level to 0Db


Now turn up the main output until you think it's going to be about loud enough. You may want to guage this by using some pre-recorded music (that you know well) on the tape in, and you may also want to use that to set the shape of the 10-channel (on the Phonics) graphic until it sounds best to your ears. If you have a tape of yourselves that you like it is good for this, but if you haven't then someone who sounds a bit like you is good too, but the most important thing is that you know what the tape is supposed to sound like eg on a good hifi.

Now turn up the fader (the last knob on the channel) until that channel is about loud enough. Now turn it down a bit because when you get the rest on the whole thing will sound louder. You will probably want to juggle the fader and the main output controls to get the point onthe fader you are actually going to be using at about 5 or 6 out of 10. Now adjust the tone controls (and the FX) on the channel by trial and error until the sound sounds best (you may want to come back and do this again when all the other channels are done because the "best" sound as a solo sound is not necessarily the "best" sound in a mix, and when you do this you are going to need to turn all the other channels down a bit to make the one you want to judge stand out a little. Good mixers have a solo button to make that easier.

You have now done one channel. Do the rest.

The lights you were watching, if I identify them correctly, flash green when the amp realises you are giving it some signal, and red when ther is too much. If you got them green only a couple of times, you can turn the main up lots yet!

How does the sound of the other acoustic guitar compare to yours? Can you borrow guitars that you know "plug" well to compare to yours?
Taylor and Takamine represent the typical "I like that" sound that sound men usually go for.   A Fishman undersaddle and preamp for about £130 plus fitting will sound as like that as your guitar (what is your guitar, by the way) will permit. If you want to sound more like an acoustic guitar (and are happy to be quiet enough to avoid feedback) spend about £10 on a "lapel mic" and stick it on your soundboard with blu-tak just peeping over the edge of the soundhole. You can't work like that, it will fall off, but see whether you like that sort of sound. If you want to hear more "wood" try the Ashworth stick-ons at about £30. It does feed back easily though. If you like a "ring" the I-Beam is expensive and feeds back way too easily, but some people really like the sound. I like B-band and you can often pick them up second hand quite cheap on ebay because the name is not so well known. The really really expensive systems tend to have blendable sound sources - an undersaddle and either a stick-on or a mic inside the guitar. LR Baggs do a thing that has an I-beam and an undersaddle blended, but it is about £200 I think just to buy before you start thinking about the fitting costs.