12 input balanced sum amplifier DIY project
« on: August 19, 2008, 01:17:23 PM »
A 12 input sum amplifier with balanced inputs and output.

Documents:

http://audioxxx.googlepages.com/SUM-12_schematic.pdf
http://audioxxx.googlepages.com/SUM-12_wiring.pdf
http://audioxxx.googlepages.com/SUM-12_layout_designations.pdf
http://audioxxx.googlepages.com/SUM-12_layout_values.pdf
http://audioxxx.googlepages.com/SUM-12_copper_mirror_image.pdf


Input connector (D-25 female) is placed on PCB so manual wiring between sum resistors and connector is not required.

The board is 70 x 50 mm single sided and designed so that it is suitable for home etching.

THD: 0.002%
Noise: -100 dBu (1 source connected), -90 dBu (12 sources connected)
Gain: 0 dB
Maximum level: +28 dBu

Unbalanced output: Leave R28 out and take output from the + output terminal.

**********

My other projects:

Studer 169 EQ
http://www.groupdiy.com/index.php?topic=33996.0

Neumann W492 EQ
http://www.groupdiy.com/index.php?topic=28332.0

Neumann OA10 discrete op-amp
http://www.groupdiy.com/index.php?topic=34105.0

Balancing/unbalancing amplifier
http://www.groupdiy.com/index.php?topic=29333.0
« Last Edit: September 01, 2009, 02:07:54 AM by audiox »


livingnote

12 input balanced sum amplifier DIY project
« Reply #1 on: August 21, 2008, 12:48:39 PM »
That's pretty. Nice little 10K grave, too ;)
My Stuff: Livingnote's META

Quote from: emrr
F-in' hook some Sh*t up and see if it catches on fire

Mobius

    Beautiful Resort City of Chicago
  • Posts: 11
12 input balanced sum amplifier DIY project
« Reply #2 on: August 21, 2008, 08:08:55 PM »
Can you explain the purpose of R27? Since it parallels R28 all it does is reduce the feedback resistance to 5K.  Is that what you want?

Matthew
Success is on the other side of failure - so we're halfway there!

okgb

12 input balanced sum amplifier DIY project
« Reply #3 on: August 21, 2008, 11:34:50 PM »
nice effort & package
although i plan to build a passive one ,
i'll support you with a order if it gets there
GKB Audio / Greg Boboski

12 input balanced sum amplifier DIY project
« Reply #4 on: August 22, 2008, 03:08:56 AM »
Quote from: "Mobius"
Can you explain the purpose of R27? Since it parallels R28 all it does is reduce the feedback resistance to 5K.  Is that what you want?

Matthew


Yes. Gain of the sum must be -6 dB because the output stage raises the level by 6 dB.

tongenerator

Re: 12 input balanced sum amplifier DIY project
« Reply #5 on: February 06, 2010, 01:49:32 PM »
can i use this to create AUX Output? what would be the resistor value when i use for example only 8 channels or 32 channels.
i want to make 8 Aux Outs... and use 16 or 20 Input Channels. thanks for any help

JohnRoberts

Re: 12 input balanced sum amplifier DIY project
« Reply #6 on: February 06, 2010, 04:01:16 PM »
Simple is good. Nice job.

Since you've already got that unused 5532 section just sitting there, what about configuring the output 5532 as two independent differential to single ended amps (with opposite polarity), each fed by both sum amps. This gives us two identical (but opposite polarity) SE outputs, that when both are used, gives us a balanced/differential output.

I would run the two sum amps at -6dB or less, with the diff amps at unity or whatever to make overall unity gain. The sum amps that are working harder, can use the few dB more loop gain margin.

In general adding an opamp is not an obvious recipe for improving any circuit design but I like the symmetry of identical + and - audio paths, while there may be some subtle differences between using 5532 inverting or noninverting (in diff stage).

 I wouldn't be surprised if what I suggest has already been done before by someone else.

JR


 
Visit https://circularscience.com to hear what properly "cleared" drums sound like.

Re: 12 input balanced sum amplifier DIY project
« Reply #7 on: February 07, 2010, 07:08:56 AM »
Simple is good.

That was the idea behind this project. I think that was also the reason why the project never came popular despite very good specs. It can't be good because it looks so simple (not enough manual wiring and exotic components).

what about configuring the output 5532 as two independent differential to single ended amps (with opposite polarity), each fed by both sum amps.

Why not. Slightly more noise and slightly worse CMRR (despite "unsymmetry" this circuit has surprisingly good CMRR). But 5 more resistors could make it complex enough to be convincing...

JohnRoberts

Re: 12 input balanced sum amplifier DIY project
« Reply #8 on: February 07, 2010, 01:32:13 PM »
Sorry I didn't realize this was such an old thread...

never mind...

JR
Visit https://circularscience.com to hear what properly "cleared" drums sound like.

RedNoise

Re: 12 input balanced sum amplifier DIY project
« Reply #9 on: February 07, 2010, 02:54:09 PM »
noob question : is there a simple way to get a 24 input sum amplifier ? :P
If your neighbour is hunger : don't give him fish , teach him how to fish ...
if you don't like it don't buy it ;-)  [Wolker Texas Ranger] ( ;-) )


gemini86

Re: 12 input balanced sum amplifier DIY project
« Reply #10 on: February 07, 2010, 04:18:39 PM »
noob question : is there a simple way to get a 24 input sum amplifier ? :P

buy one?

...sorry, couldn't resist.

More specifics? Looking for schematics, kits, ???
- Rodney

"...you better call Kenny Loggins, 'cause you're in the danger zone."

RedNoise

Re: 12 input balanced sum amplifier DIY project
« Reply #11 on: February 07, 2010, 04:33:40 PM »
Ahahahaaaa...
I meant : based on this DIY project , is there a simple way to get 24 channels summing instead of 12?Maybe a mathematic law to apply to the resistors for example?Sorry I'm not an ohm law guru...
Many thanks for your help Gemini86 , your targeted my aim so precisely!
Cheers! ;D
If your neighbour is hunger : don't give him fish , teach him how to fish ...
if you don't like it don't buy it ;-)  [Wolker Texas Ranger] ( ;-) )

tongenerator

Re: 12 input balanced sum amplifier DIY project
« Reply #12 on: February 07, 2010, 04:43:31 PM »
noob question : is there a simple way to get a 24 input sum amplifier ? :P

i found a site wich is explaining the hole story very good.. unfortunatly the background picture makes it hard to read.. i had to mark it to be able to read it.. but it is a realy good page: http://www.all-electric.com/schematic/simp_mix.htm

and this one is also good... it has howto giude and shematics: http://www.forsselltech.com/do-it-yourself.html

RedNoise

Re: 12 input balanced sum amplifier DIY project
« Reply #13 on: February 07, 2010, 05:19:49 PM »
Thanks Tongenerator!A lot of readings!Thankssss!
If your neighbour is hunger : don't give him fish , teach him how to fish ...
if you don't like it don't buy it ;-)  [Wolker Texas Ranger] ( ;-) )

Re: 12 input balanced sum amplifier DIY project
« Reply #14 on: February 15, 2010, 01:28:26 PM »
noob question : is there a simple way to get a 24 input sum amplifier ? :P

Just more resistors. You can use a second PCB for the extra inputs (just leave out the opamps and place wire links between the summing points of the two boards).

AUDIO-ON

Re: 12 input balanced sum amplifier DIY project
« Reply #15 on: June 01, 2010, 07:56:45 AM »
Hi Audiox!
A stupid, I think, question:
12 inputs, mono.
For stereo, 24 inputs, two circuits.

Is it a must, putting 12 inputs, or can there be only 8 with the same configuration?
Thanks
MUSIC!!!

W DeMarco

Re: 12 input balanced sum amplifier DIY project
« Reply #16 on: June 01, 2010, 11:18:40 AM »
Audio on, search around the forum a bit, there are some really well documented passive threads with theory.

Re: 12 input balanced sum amplifier DIY project
« Reply #17 on: June 03, 2010, 04:26:29 PM »
A stupid, I think, question: 12 inputs, mono. For stereo, 24 inputs, two circuits.

See my answer in a post before yours.

Is it a must, putting 12 inputs, or can there be only 8 with the same configuration?

You can leave four of the inputs unconnected. It doesn't affect the overall gain.

Re: 12 input balanced sum amplifier DIY project
« Reply #18 on: June 03, 2010, 05:09:12 PM »
This is probably obvious, but for some reason it isn't coming to me.  I'm still new.

The DB25 cable has only one ground, which I understand.  Obviously they all share the ground...but how do you go about wiring the other side of that?  Say to 12 TRS cables.  You just plug all the grounds into that one pin?  Would that not get a little crowded lol?  Maybe connect all the grounds from the TRS's off the connector and run one lead to the pin?

Thanks.

Re: 12 input balanced sum amplifier DIY project
« Reply #19 on: June 07, 2010, 05:14:17 PM »
bump for my last question...

Plus, what would be the difference in sound between this and a passive one? 


 

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