Trying to design a Simple Active Mixer on sinlge voltage

acidblue · Joined: Jun 26, 2009 Posts: 226 Location: The Darkside

I've done lots of googling and reading about op-amps and mixers.
Seems most mixers use dual voltage, +/-12-15v.
Trying to design one that uses single voltage.

Not sure if I got the virtual ground part correct.
Any insight would be appreciated.

This is what I have so far.

Mixer.ps

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rich decibels · Posted: Thu Oct 14, 2010 6:00 pm Post subject:

http://www.beavisaudio.com/techpages/blocksfragments/

scroll down to the 'mixers' section.

excellent starting point, at least.

Draal · Posted: Thu Oct 14, 2010 7:55 pm Post subject:

Check the active mixer (schematic 2) here:
http://www.all-electric.com/schematic/simp_mix.htm

I built it with a few changes. Read my progress from a thread I started a lil' while back. Page 2 has the schematic as well as my substitutions : http://electro-music.com/forum/topic-42776.html

Hope it helps Very Happy

!

acidblue · Joined: Jun 26, 2009 Posts: 226 Location: The Darkside

Thanks..
So that will run on a single voltage?
Noticed it's called "virtual earth active mixer", if I read google correctly
A virtual ground is basically a voltage divider on the input,(+) to
cut the voltage in half.

Is that case here?

Draal · Posted: Fri Oct 15, 2010 5:17 am Post subject:

Yep, it'll work on single supply. I've used it when I ran my lunetta on a 9 volt battery for a while and it's still loud and proud running on my new regulated 5 volt wallwart.

No bipolar stuff going on here. I have to be more awake to remember the concept of virtual earth though Laughing

! Scroll down to the active mixer section here; it explains it better than I can:
http://sound.westhost.com/articles/audio-mixing.htm

I think it's a very decent active mixer and pretty simple to build.

acidblue · Joined: Jun 26, 2009 Posts: 226 Location: The Darkside

Cool
Thanks.

Top Top · Joined: Feb 02, 2010 Posts: 266 Location: California

General guitar gadgets mini mixer. Simple one chip mixer, works well.

If you want one with input gains (to plug in guitars or mics), I made a modified version, also with power regulation to run off of a wall wart without humming. If you don't need that and just want to run on a 9v battery, then omit the LM317 and caps/resistors connected to it, and hook the + of the battery to the line where the four 10k resistors are, and negative terminal to the bottom line, which is ground:

Posted Image, might have been reduced in size. Click Image to view fullscreen.

Posted Image, might have been reduced in size. Click Image to view fullscreen.

NOTE: if you build it, make those .47uF caps NON POLAR. That was a mistake.

textual · Posted: Fri Oct 29, 2010 9:29 am Post subject:

I am using this design from Ray Wilson's site...
I have 2 mixers in my system and this works quite well. Any general op amp will work. I added pots for volume of each input. Log pots are better as well -linear gives less actual 'control' over the difference between loud and soft volumes...

simple_opamp_audio_mixer.gif

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