this is my first post and i'm going in school about electronics so this is my last year and i'm doin a audio mixer but i dont know how to desrcibe it ....if someone could write mi an e mail about this sheme....tnx ops:
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http://www.elektronika.ba/el.sheme/?...&iz_idgrupa=12
just scroll down the page and you will see a gif file for download cause its on another language
btw my e mail : dj_incoxes@hotmail.com

 

i think it is in croat but i never got to the x.gif file cannot find it sorry

 

http://rapidshare.de/files/17976748/untitled.JPG.html
here is another link....

 

It's only a simple opamp mixer, there are plenty of others on the internet, or it's simple to design your own - and this one doesn't impress me much, I don't like to see gain controls wired that way!. It does add crude passive tone controls, but I would prefer to see active baxendall ones.

Attached Images

mixer_213.gif (4.4 KB, 275 views)

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sorry but i dont know much about electronics i asked if u could describe how does it works...didnt want to impress u looking 4 help....

 

OK.

An opamp is an 'operational amplifier', they were originally designed for analogue computers, but with the advent of IC's have become a popular electronic component.

U1 is configured as an 'adder', originally used to add voltages (numbers) together in the analogue computers - in this case it's used to 'add' (mix in audio terms) the three signals together. The three input controls adjust the percentage of each signal added to the mix.

U1 is followed by passive tone controls, for bass and treble, being passive these lose considerable amounts of signal, so U1 needs enough gain to overcome this.

The last section, U2, is simply a buffer, which gives a low impedance output to feed to an amplifier or recorder. Without this the fairly low input impedance of the following circuits would load the tone controls, and stop the circuit functioning correctly.

If you actually want to build a small mixer like this, let us know and we can make suggestions.

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w.r.t. that cct, arnt the OPAMPS the wrong way round? both have positive feedback?

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Yes they are wrong! - I just copied the circuit off the original link given, the -ve and +ve inputs just need changing over on both opamps.

I would also like to see the three input resistors and gain pots swopped over, I REALLY don't like to see them that way

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tnx a lot nigel...i am a dj and when i saw a mixer i thouhgt wooow look i can make this my final exam but as you see i dont have clue about it ops: ops: ops:

 

It's some what more complicated, but it is stereo, and designed for DJ use, so how about

http://users.otenet.gr/~athsam/2ch_mixer_eng.htm

or here

http://users.otenet.gr/~athsam/Audio_mixer_6_ch_ENG.htm

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PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

Somebody messed-up the 1st schematic because it looks different and is corrected on Aaron's site today:

Attached Images

mixer.png (6.4 KB, 239 views)

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Uncle $crooge

 

Here is Aaron's parts list for his mixer:

Attached Images

mixer_s_parts_list.png (13.3 KB, 235 views)

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Uncle $crooge

 

Hi Guys

Looking at that circuit ive never seen capacitors wired across the supplies like that before.

Are these just decoupling capacitors. Seems strange to put them on the op - amp supply rails??????

 

Are you serious?.

It's VITAL to have decoupling capacitors on the supply rails, with ones as close to the chips as possible highly recommended.

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yeah i am, most circuit ive seen never have them

unless its something you should assume regardless if they are thereor not.

Just as an example here ive found a circuit diagram on this board just a few posts down

Attached Images

la-light_20comp_166.jpg (50.8 KB, 187 views)