My unbalanced line mixer design needs something... - diyAudio
Go Back   Home > Forums > Source & Line > Analog Line Level

Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 28th February 2010, 11:51 PM   #1
diyAudio Member
 
Join Date: Mar 2007
Send a message via AIM to thefunkybeat
Post My unbalanced line mixer design needs something...

So, a buddy of mine does music production for video games and has a lot of synths and sound modules. He asked me to build him a summing amplifier.

He wants to sum all the signals from all his synths and samplers and things into one stereo pair. Since he's controlling volume and panning via MIDI sequences, he doesn't need ANY controls at all; just a lot of stereo inputs that get blended into one stereo output.

So, I've decided to build him an unbalanced stereo summing bus with 16 stereo inputs. (He doesn't need that many, but I wanted to make sure he has some extra inputs for when he buys more sound modules later.) I don't have an electrical engineering education myself, but I'm pretty good with schematics and putting things together. After some research, I found this:
MIXER 6+ channel in English

I figured I'd take the unbalanced stereo input schematic, multiply that 16 times, skip the EQ section and go right to the summing amp. So far my plans look like this:
Click the image to open in full size.

... but... I feel like I'm missing something... My intuition is telling me I need a cap or a resistor or both on each Left and Right output of each unbalanced stereo line in circuit... or maybe just a couple of caps on the Left and Right inputs of the master summing amp?

What am I missing here?
__________________
WWW.HIPAUDIO.COM
  Reply With Quote
Old 1st March 2010, 02:37 AM   #2
diyAudio Member
 
Speedskater's Avatar
 
Join Date: Sep 2002
Location: Lakewood, Ohio
That circuit is not going to work at all. The output of each input IC will try to drive the output terminal of all the other input IC's. The output impedance of an IC is just over 0 Ohms so all the IC's are driving almost dead shorts. Normally a summing bus is connected to the negative input and each signal has it's own input resistor (maybe 1K to 10K)
__________________
Kevin
  Reply With Quote
Old 1st March 2010, 08:24 AM   #3
diyAudio Member
 
Join Date: Mar 2007
Send a message via AIM to thefunkybeat
Quote:
Originally Posted by Speedskater View Post
That circuit is not going to work at all. The output of each input IC will try to drive the output terminal of all the other input IC's. The output impedance of an IC is just over 0 Ohms so all the IC's are driving almost dead shorts. Normally a summing bus is connected to the negative input and each signal has it's own input resistor (maybe 1K to 10K)
Well, I'm sure some parts will work, but others won't. So, you're saying I need a resistor on the Left and Right outputs of each channel huh? ... and maybe rework the summing amp a little? I'll do some more research on that summing amps using the inverting input thing... I've seen that too.

Anybody else have suggestions? tips? solutions?

Thanks!
__________________
WWW.HIPAUDIO.COM
  Reply With Quote
Old 1st March 2010, 10:11 AM   #4
wahab is offline wahab  Algeria
diyAudio Member
 
Join Date: Nov 2009
Location: algeria/france
You can use an inverting amp to sum the signals
through a resistor for each channel, but with 16 inputs,
the noise gain will be very high.
  Reply With Quote
Old 3rd March 2010, 08:08 PM   #5
zdavesf is offline zdavesf  Canada
diyAudio Member
 
Join Date: Apr 2006
Location: alberta canada
read this and subtract what you need.

High Quality Sound Mixer

This project can become time consuming very quickly. input and output buffers could both be improved. if your buddy is looking for a relatively cheap low noise mixer and wants it fast i would suggest maybe looking at Musician's Friend | Your Online Music Instrument & Pro Audio Store | Best Prices, Great Service

I do not want to discourage any DIY project but Realize if you are going with a simple design it will take some R&D to get it tweaked. Best of luck. Like mentioned before use a inverting opamp configuration as a summing buss... i believe most commercial mixers use 4K7 feedback resistors (or there abouts) due to lowest noise. usually no more then 4 signals per mixer (ie 4 groups of 4 mixed together with another mixer).

Dave
__________________
we all have to start somewhere...

Last edited by zdavesf; 3rd March 2010 at 08:24 PM.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Intentionally Unbalanced mixer? dlciii Car Audio 16 11th March 2009 05:39 AM
Unbalanced to Balanced Line Level XFMR wrenchone Solid State 8 22nd October 2005 09:06 PM
Unbalanced Line Driver punchpeanut Solid State 7 12th December 2003 02:31 PM
Unbalanced Line Driver punchpeanut Solid State 1 11th December 2003 10:56 AM
unbalanced line stage almost completed Hanzwillem Pass Labs 15 24th October 2003 02:01 PM


New To Site? Need Help?

All times are GMT. The time now is 04:55 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2