build basic audio mixer (4 channels to 1)?

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janklug

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Joined 2004
epibreren.com/klug
hi,

i'm new to this forum (and basically to audio electronics, too, so please forgive any newbie mistakes ;-) )

(the first one was to post the same question to the digital forum, but apparently not all things containing IC's are digital ;) - so once again..)

i'm planning to build a very basic audio mixer, that should combine 4 channels (2 dynamic mics, 2 line level instruments) to 1 line level channel.

the level of the in's should be set individually, and i'd like to have a master fader, too.

i've searched the internet & found several designs that (more or less) seem to fulfil these wishes; unfortunately, i don't know the used amplification methods & their pros/cons, so i can't decide what solution would sound & work best...

does anybody have any idea wich of the following schematics to prefer, and/or answers to the related questions on that design?
any help greatly appreciated!

http://www.redcircuits.com//Page53.htm (looks like the best choice to me)
(question 1: do i need the full 'input module' also for the line level inputs?
question 2: what can be omitted to make it just a mono out?)

http://www-fa.upc.es/websfa/lab/111/audio/audmixer.txt
(question on this: Audio Taper pots - are that just logarithmic pots?)

http://home.maine.rr.com/randylinscott/may20.htm
(- question 1: does it need 9V power, or is that +9V / -9V symmetrical power? just heard of the existance of symmetrical power today ;-)
-question 2: what kind of caps are those? the 100uf seem to be polarized, but what about the 10uf at the outputs?!)

http://www.zen22142.zen.co.uk/Circuits/Audio/6ipmix.htm
(question 1: what are those opAmps? which model to choose for that?
question 2: this actually USES a symmetrical 9V power source, right?)

well, i found more, but these seemed to be fitting best.

thanks & greetings,

jan
 
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paulb

Member
Joined 2001
janklug said:
http://www.redcircuits.com//Page53.htm (looks like the best choice to me)
(question 1: do i need the full 'input module' also for the line level inputs?
> No.
question 2: what can be omitted to make it just a mono out?)
> The pan pots and either the left or right channel mixer amps.

http://www-fa.upc.es/websfa/lab/111/audio/audmixer.txt
(question on this: Audio Taper pots - are that just logarithmic pots?)
> audio taper = logarithmic taper

http://home.maine.rr.com/randylinscott/may20.htm
(- question 1: does it need 9V power, or is that +9V / -9V symmetrical power? just heard of the existance of symmetrical power today ;-)
> +/-9V. Two 9V batteries will do it.

-question 2: what kind of caps are those? the 100uf seem to be polarized, but what about the 10uf at the outputs?!)
> 10 uF non-polarized electrolytics would be best, but normal polarized electrolytics will also work. If the input impedance of whatever it is feeding is higher than 2K, you can reduce the capacitor size accordingly.
> Careful with this circuit. There is no such thing as an LM353, it's actually an LF353 which could be replaced by a TL072.

http://www.zen22142.zen.co.uk/Circuits/Audio/6ipmix.htm
(question 1: what are those opAmps? which model to choose for that?
> TL072 will work. You will need bypass capacitors close to each IC, one each on the +ve and -ve supplies. 0.1uF (100nF) will work.

question 2: this actually USES a symmetrical 9V power source, right?)
> Yes.
well, i found more, but these seemed to be fitting best.

thanks & greetings,

jan
Click to expand...

Also see http://headwize.com/projects/showfile.php?file=opamp_prj.htm
 
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paulb

Member
Joined 2001
janklug said:
thanks for having a look into this, paulb!

i think i'll go for the modular version at http://www.redcircuits.com//Page53.htm.

> The pan pots and either the left or right channel mixer amps.

ok!
i wondered though if for example R1, C1 and R2 should stay in there, or if they should be skipped together with the pan pot..

thans again & greetings,

Jan
Click to expand...
R1, R2 and P1 can be skipped. You need to keep C1, connected directly to the wiper of P1.
 
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OKI

Member
Joined 2004
Wow - very weird. I have just gone through the same routine myself.

I decided to build a mixer (with limited electronics knowledge) and searched the web for various circuits.

I too chose the redcircuits / page 53 idea and ordered the parts earlier this week - I have only started building the circuit last night...but we'll see. Hope should have the tone control section ready for testing tomorrow. Very strange.

The only difference is that I'm splitting the signal after the gain control to create a PFL button and add VU meter. Otherwise its the same project.

Anyway, I was just wondering how you got on...anything I should look out for or tips etc?

Thanks very much,

OKI
 
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