Mixers are always used both during recordings and gigs - always. If you have got a band you'll need one, otherwise you will need a single amp for each one well if you use tube amps for each one, it'll be better but not everybody can afford him the joy of the tube amp. So you will again need mixer to connect all the instruments to an amp and than to the speakers.
What a problem? will ask some of the readers I'll use 2 inputs to one output little jack adapters connecting some of these together will give me the needed amount of inputs to my amp + it'll cost about 5 or 6 $ max, whilst the cheapest mixer with 3 inputs costs 30 dollar which has got no options to control except volume.
But they'll be wrong in that case mixer not only connects yr instruments but controls each instrument's volume separately + good mixers have got EQ's for each line, phantom power (which won't be used that much often in garage/little bands cause condenser mic costs an arm and a leg and they are not used during practicing), some of them has got FX They will be useful both in studios and practices There are also PM's (Power Mixers) which have just got an amp on Main Mix Output cool right?
Hmm so when buying a mixer you have to decide what you need. There are dozens of mixers so it'll be hard to decide. Well first things you have to think of are what budget dya have? And what options dya need most of all. (well these are the only things you have to decide) Mixers begin from 30 dollars to millions (ouch! ) Hmm well if you will be gathering the money first(if ya don have the cash yet) than better first see how much dya need otherwise start looking for available options in the desirable price.
Like I said the cheapest mixer costs 30 dollar it has got nothing but 4 mono line ins with volume control and only that sux better to add at least extra 30 dollars and buy Behringer Xenyx 802. Well there is Xenyx 502 as well which cost less but they got only 3 inputs which in most case are useless (Look, you'll have your guitar plugged, bass, mic or two (if you need backing vocals), 2nd guitar (maybe) and/or keyboard) so I'd say minimum 4 is the minimum.
Now deciding what options do we need?
I'll go on with examples on Xenyx 802 as it's the cheapest but yet useful mixer. Ok now first there are several types of line-ins Mono and stereo. Mono's got 2 jacks which can't be used both at a time 1st is 1/4 jacks (You use them to plug guitars and so) and XLR jacks which are used for mics (some including UB802 has got phantom power for condenser mic powers through the same jack) Mono's mostly have pre-amps The first thing is Trim Knob. Than comes the EQ (Equalizer) for each mono line after comes FX (Effects) knob (will talk about him later) and after comes the PAN (Panorama) knob - rotating it will just pan the sound to the left or right speaker signal And than, comes the level which comes in two versions - whether knob or slider (the 2nd version is used on expensive mixers and is more comfortable (it's faster and you can see the volume visually)) it controls the volume of the line in.
The stereo line-ins contain from two 1/4" jacks, and all the same stuff as the monos (in little mixers sometimes they don't put EQ's for stereo line-ins as for example Xenyx 1002 or Xenyx 1202) they also have got BAL (Balance) knob in place of Pan turning to the left will mute the right signal and you will only hear the signal coming from current stereo input's left jack and vise versa You can use the stereo plugs for two different instruments so turning the BAL control will control the volume (both at a time)
Now bout the EQ's they put 3 band EQ's on mixers but sometimes there are some extra knobs like *treble or mid* Freq which controls what frequencies control the band controller. But more often they put buttons on treble or mid like Boost Cut, Hi Cut and so There are also the Peak Leds which show if the line falls into overdrive on some mixers (like I said, if they've got pre-amps (well nowadays all the mixers got them) there are the gain or trim knob which doesn't need explanations right? (Hmm if they do than just read further)
Now bout FX knob and Aux send return stuff
You'll see some additional jacks named FX send and AUX return. FX send jack sends the signal to an external effect's device such as Delay, reverb and so. Than the signal comes back to the mixer and connects to the AUX input. The FX knob on each line in controls wet signal's level. The AUX return inputs can be also used like additional inputs. The Aux stuff works like this the sound comes into the mixer passes all the stuff like pre-amp EQ and is being copied the copy than is being sent to the FX send jack. Than it comes back through the AUX return jacks (they're usually stereo) and the sound is sent to the main mix output (not to the same channel it was taken from) There also are AUX RETURN knobs which control the volume of the effects So these also can be used as additional inputs.
There's also a button FX to Control Room/Headphones which send the AUX return signal to the headphones (is pretty useful future in some cases). But some of the mixers don't have AUX returns, you use one of the free channels to have the effects back to yr mixer, plus in this case ya can have EQ on yr effect signal. On most mixers there are also the MUTE buttons at the bottom which mutes corresponding line. On more advanced mixers there are also the solo buttons which mute all other inputs, letting the corresponding line to go SOLO (you can SOLO-up more than 1 signal at a time so it's pretty useful and comfortable (for I.e. Instead of muting 8 channels from 10 ya can just Solo-up the other 2).
There are also the tape in and tape out. You can connect a tape deck CD player or other external signal source to the mixer. The tape out is wired parallel to the main out and is used to take the main signal to recording devices and so You can use tape in to have the signal from the recording devise back to your mixer and sent to the Control room to monitor whether the recording device overloads or does it's work.
There are also the phones (control room) level and outputs - Use them as ya want. There also meet buttons like tape to phones which takes tape signal to phones, tape to mix which takes the tape signal to the Main Mix. Some have also the Fx to phones which send to the Phones only dry signals not the main mix. Than comes the main mix level (master level) which controls the volume of the Main Mix. There are also Control LEDS these are the Main Mix's Led VU Meter. They Show whether the line is overridden or no.
Somes have also these buttons on every channel named PFL (Pre Fade Listen ) it just makes the VU meter to show the corresponding channel's signal to check in no overdrive. Now about the Gain/Trim knob. Use these to make yr signal stay at 0 on VU meter.
First trim them so you'll get the clean tone and than use your channel vol controller to control the vol. Overloading it will bring you to undesirable overdrive Note: when the overdrive is sometimes desirable with analog recorders, the digital ones fall drive faster and make yr record useless. Oh and forgot to say about Phantom power nothing too special - there's only a button named phantom power which turns it on wait for a minute or so till the system will be stabilized.
So these are the basics. Loads of mixers got more than one AUX channel which let you to connect different channels to different FX. Somes has got separate Master Level Knobs for left and right signals or additional outputs (in this case there are additional buttons like FX to alt 3-4 outputs, Channel to alt 3-4 and so which choose whether the signal is being sent to the Main output or to the extra ones? ) I can't think of any moer general/important options yet as there are dozens of them (monitors and sliders and so)I will aso write the second part if you want and it will be about using the Mixers for nebies.
Feel free to ask anything you want and make any correction you think is being miswrote or dismissed. Also feel free to contact me whether by UG or by my e-mail.