Mixer circuit

Thread Starter

Aurbo

Joined May 6, 2005
9
Greetings,


I need to take 4 audio inputs from 4 separate (low power) MP3 players and combine then so they will all play off a single set of desktop computer speakers.

ganging all the inputs right now lowers the output and the distortion increases for each input added.


I have been told a "Summing Amp" will work, but I cant find one that is low votage (under 12Vdc)

Will I need to isolate each input ( diode? ) prevent and back-feeding into the other units?


Anyone have a diagram that might work?

Cheers
Steve
 

David Bridgen

Joined Feb 10, 2005
278
Originally posted by Aurbo@Jun 17 2005, 07:25 PM
So +power goes to pin 3 instead of pin 7?
[post=8595]Quoted post[/post]​
No Steve.
The potential divider provides a point which is mid-way between the supply rails. With a 12V supply, for instance, it is at 6V.
With pin 3 at mid-rail the output will sit at 6V without a signal (it will have a d.c. offset) but swing symetrically around 6V with a signal.

Without the mid rail connection the output would sit at or near 0V without a signal and couldn't respond correctly to the input.

If the 6V, or whatever, offset is a problem, e.g. the device driven by the output is direct coupled (unlikely) stick a capacitor in series with the output.
 

pinball8

Joined Jun 12, 2005
16
Originally posted by Aurbo@Jun 14 2005, 05:00 PM
Greetings,
I need to take 4 audio inputs from 4 separate (low power) MP3 players and combine then so they will all play off a single set of desktop computer speakers.

ganging all the inputs right now lowers the output and the distortion increases for each input added.
I have been told a "Summing Amp" will work, but I cant find one that is low votage (under 12Vdc)

Will I need to isolate each input ( diode? ) prevent and back-feeding into the other units?
Anyone have a diagram that might work?

Cheers
Steve
[post=8498]Quoted post[/post]​
buy a small audio mixing board.
 
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