basically the use a IC with 3 op-amps and some pots to both ampligy the sound and control the volume which is exaclty what I want and need
my problem is since im noobish to electronics, do I need to change any of those resistors or condensator vaalues since the Arduino works on 5v and not 12v!??
If so some can guide me how can I determine (the process) of all those value? Ill be glad to work a bit and learn it for my self but im lost now
When you set the pot to 0 Ohm, then it acts as a buffer (Gain = 1) and when the pot is at maximum, your gain would be 3.2 times your input. Depending on what your input is, you may need to use higher pots, but I think it should be fine.
well Im not connecting this (the final project) to small speakr but normal speakers, even pre-amp concert speakers so dont know then if I should go with your recomendation??
another thing... I just noticed the +12V -12V, that probably means the other project uses a AC supply and not DC no?? I guess ill have to work a bit with the diagram on the bread board to make it work?
My only fear is to short my sound chips :).
what will be the critearia to choose the propem op-amp ??
You have to make a split supply from the single ended 5V supply.
Arduino Ground becomes -2.5V
Arduino +5V becomes +2.5v
then your amplifier ground is connected to the mid point of two 1K resistors as a potential divider going between the +5 and ground.
You should AC couple the audio inputs, that is connect then through capacitors.
well Im not connecting this (the final project) to small speakr but normal speakers, even pre-amp concert speakers so dont know then if I should go with your recomendation??
if I understand what you are doing, a mixer really isn't what you want. And the regular op-amps don't have enough power (Watts & current) to drive a 4 or 8 ohm speaker.
A mixer is for mixing sounds... i.e. With a 3-input mixer, you could blend two guitars and a microphone (assuming they've been pre-amplified).
You can drive a preamp directly from the Arduino. You just need a series capacitor (maybe 1uF) to knock-out the DC component. A volume control (pot) would be a good idea too. A series resistor (maybe 1K) wouldn't hurt either. It will limit the current so that you don't wipe-out the Arduino if you accidently short-out the output (or if you accidently connect a speaker).
It can be fun to build stuff, but unless you want something unique that you can't buy, it's often cheaper to buy something already built. The op-amps & electronic parts are cheap, but when you start adding a power supply, knobs & switches, and put it in a nice box, you usually end-up spending more. Manufacturers can buy parts cheaper, they use low-cost labor (China, etc.), and there is very little per-unit labor on an assembly line...