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I have a problem!!

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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.
 

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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 :D looking 4 help....
 
roby said:
sorry but i dont know much about electronics i asked if u could describe how does it works...didnt want to impress u :D 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.
 
w.r.t. that cct, arnt the OPAMPS the wrong way round? both have positive feedback?
 
Styx said:
w.r.t. that cct, arnt the OPAMPS the wrong way round? both have positive feedback?

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
 
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 :oops: :oops: :oops:
 
roby said:
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 :oops: :oops: :oops:

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

**broken link removed**

or here

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

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Here is Aaron's parts list for his mixer:
 

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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??????
 
andy257 said:
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.
 
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
 

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YUP because MOST cct you seen do NOT show then doesn't mean they do NOT exist

ALL supply rails need to be decoupled!!! end of!

THAT cct you just posted doesn't even show where the +v and -V come from as far as you don't know there is more then likely going to be decoupling on that sheet


decoupling is NEEDED

an opamp (and other silicon) need to see a steady voltage source connected to the rail's Capacitors right next to the chips ensure that any noise is coupled to earth as well a de-coupling any supply leads (that would make the supply rail look more like a current-source due to inductance)


go read the bible (horitz & Hill)
 
Yes, they often are not shown, but they are essential in almost any electronic circuit - for one thing they keep the supply rails at the same AC potential, which is a requirement for most electronic circuits.
 
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