Stereo Mini Mixer

[septi0]

I just made a passive mixer to combine line audio signals.
I made it using this schematic-> https://lh4.googleusercontent.com/-zLslc_bNFq4/U0V3MHqPuyI/AAAAAAAAA4A/7JTy8kEdXsU/w787-h413-no/Implement1.gif
Is pretty cool except that the attenuation is kinda annoying...Can this schematic be modified somehow to boost a little bit the output signal but using just a 9v battery and keep that 10k resistors and pots?

I tried to make a circuit using a TL074 but it was a fiasco, so I thought to ask you guys for a solution.

[wavley]

I just made a passive mixer to combine line audio signals.
I made it using this schematic-> https://lh4.googleusercontent.com/-zLslc_bNFq4/U0V3MHqPuyI/AAAAAAAAA4A/7JTy8kEdXsU/w787-h413-no/Implement1.gif
Is pretty cool except that the attenuation is kinda annoying...Can this schematic be modified somehow to boost a little bit the output signal but using just a 9v battery and keep that 10k resistors and pots?

I tried to make a circuit using a TL074 but it was a fiasco, so I thought to ask you guys for a solution.

Maybe slapping a 5532 on the output for some make-up gain would do some good?

[septi0]

Does the schematic from link above looks ok?(keeping my 10k resistors instead of that 22k)

http://www.next.gr/uploads/135-8992.png

[wavley]

Does the schematic from link above looks ok?(keeping my 10k resistors instead of that 22k)

http://www.next.gr/uploads/135-8992.png

That would probably work just fine, for stereo you would need two, that's why I was thinking a single dual op amp would be the way to go, plus the 5532 is a mixer standard.  The up side of the discrete version is that everybody probably has decent npn's laying around.

[septi0]

Got any schematic?I couldn't find any using 5532.

[septi0]

Still looking for suggestions.

[wavley]

Got any schematic?I couldn't find any using 5532.

You could just tack the op amp portion for Jack Orman's simple mixer on the end and double it for stereo.



Here's the data sheet for the 5532. http://www.ti.com/lit/ds/symlink/ne5532.pdf  Honestly any dual op amp should do fine, 5532's are a mixer standard so that's why I suggested it

[PRR]

> Maybe slapping a 5532

He "tried to make a circuit using a TL074 but it was a fiasco"; I don't see any difference with a 5532?

(Yes, if his "fiasco" is a dB of hiss.... )

> using a TL074 but it was a fiasco

I think that's your hook. What did you do? What did it do?

[septi0]

I tried to do something like this -> http://forum.allaboutcircuits.com/image_cache/httpwww.ecelab.comcircuitaudiomixer.jpg using a tl074 but I used a 9v battery to power the op amp...like battery + to vcc + and battery - to vcc - straight to the op amp...

[bluebunny]

If you followed that schematic directly and only substituted the bipolar supply for a single battery, then the + input on the opamp needs to be biased half-way between the power rails (so to ~4.5V).

[septi0]

So...If I follow the schematic from above it will work?





L.E. Or this one:

[septi0]

I decided to make the circuit with tranzistors...using that schematic from post #2.
I modified it for stereo..Could anyone look at it and tell me if I made it ok for veroboard?

[wavley]

> Maybe slapping a 5532

He "tried to make a circuit using a TL074 but it was a fiasco"; I don't see any difference with a 5532?

(Yes, if his "fiasco" is a dB of hiss.... )

> using a TL074 but it was a fiasco

I think that's your hook. What did you do? What did it do?

I guess I just assumed because he was using a quad op amp and I didn't see any use for a quad at the end of the circuit that he was using it before the summing and that's why I suggested a dual at the end of the circuit as make up gain instead driving, just seemed like better gain staging to me.

But you know what assuming does, looks like the problem was bipolar supply.

[septi0]

Problem solved!  I made the schematic from above using transistors (bc547b), with a few modifications works like a charm.

Thank you all for your suggestions and replies.

[jishnudg]

On a related note, are there any verified schematics of active matrix mixers?

[septi0]

And it's all done.

It looks like this:

[Kipper4]

Nice work

[noisette]

@jishndg (or smthg.)
look at this site
http://www.cgs.synth.net/
click ´modules´ and look for matrix mixer...

[jishnudg]

Thanks!

[septi0]

I made a low battery indicator and to make it more accurate for my application I need to know what is the minimum voltage that a BC547 transistor needs to operate properly.

Right now I have a 6.2v zener diode, but I want to optimize my circuit.