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Old 14th March 2011, 06:13 PM   #1
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Default Balanced Matrix Mixer Question!

Hey there y'all.

I'm looking to make a balanced line level matrix mixer for my home studio.

Everything is interfaced to the bantam patchbays. This will be too.

so far I figured I would take this project:

Project 129

and implement the DRV134 and INA134 chips at the I/O to attain a healthy balanced signal.

Does this make sense as far as economy and sound quality are concerned or should I go a simpler (or more complex :/) route?

Thanks so much!
Evan
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Old 16th March 2011, 06:41 PM   #2
zdavesf is offline zdavesf  Canada
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This project is definatley not for the faint of heart, there is alot that you need to consider. I personally have had a matrix mixer project in the back of my mind for some time. what are you using this for? I want to use it for multiple monitor feeds so i will have a line in and a direct line out to feed the main mix (or you can you the main mixers direct out). How many channels do you want (6 in 6 out, 10 in 4 out?). I would personally make pcb input cards and plug them all in to a main board where all the signal routingwill take place. you will be running signals all over the place so special care needs to be taken to ensure you are not getting degredation of signal. Depending on electronics experience and available resources this may not be that "Economic" of a project. it all depends on your needs.

Pricing at a glance
- desining your own custom pcbs ( PCB Prototypes ) about $100
- Pots + Knobs ~$4 each x 6x6 = 32*4 = $128
- drv 134 $5.75 each x 6 = $35
- ina134 $3.11 each x 6 = $20
- OPA134 $3 ...
-chasis $100-$200
- power supply $30

already over $400
or you can just buy a behringer mixer for $200 Shop Behringer | Musician's Friend

but building is way funner. Personally i would consider using op input stages (and output if you can find a good transistor buffer deisgn), but thast just me. I dont like being stuck with specialty parts if i can help it. yes these have been around for a while but i had a school project where i NEEDED some DRV134's for the PCB is designed when i acidently blew one up and needed more they were out of stock for 2 months after my deadline... I just added a output resistor to the last opa134 stage and the instructor was none the wiser, he just wanted to hear it work, and it did .

best of luck, let us know more details.

Dave
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Old 16th March 2011, 09:05 PM   #3
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I think that you'll need an inverting buffer at the mix end before the DRV134 to avoid crosstalk. The DRV134 has a connection to the positive outputs non inverting input, so you don't have the virtual ground like you do with an inverting buffer.

You can leave off the inverter at the input buffer and end up with the same number of opamps in the signal path. Just reverse the connections to the DRV134 to restore phase.

Dave's school experience is why I always buy several spares, or buy in bulk when I can. I still have over 100 OPA2134 so I build my own balanced drivers when needed. ;-)
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Old 18th March 2011, 04:04 PM   #4
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Alright.

I'm going to start working on a schem and post it up here when it feels alright.

But just to reiterate:

Is adding the 134 chips to the other circuit the best way to do this?

Also, to clarify:

I'm building this to add to my home studio which is designed largely for musical experimentation, but it will also be used for "aux send" like implementation. I want it to be balanced for my bantam patchbays.
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Old 20th March 2011, 05:11 PM   #5
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okay guys.

another couple questions:

can't I use the 5532s as a balanced line receiver?

could I use them as a balanced line driver?
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Old 21st March 2011, 04:12 PM   #6
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alright. still learning. still working on it. I've got answers to my last questions.
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Old 22nd March 2011, 06:23 PM   #7
zdavesf is offline zdavesf  Canada
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Yes you can use 5532 for inputs and outputs (use may need push/pull class AB output amp )

best place to start is to draw out a block diagram showing your input blocks mixing blocks and output blocks. After that then you just need to find/design circuits for each block and make sure the integrate with each other (impedance matching, phase shifting etc.)

Post your progress, and im sure you will get more feedback once you get into the design

Dave
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Old 12th April 2011, 05:19 AM   #8
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alright. another question:

is there a way for me to build a balanced unit that would also be comfortable taking unbalanced and sending unbalanced?

would it take a switch, or would the balanced receivers and drivers inherently be comfortable receiving and interpreting the unbalanced signals?

Can maybe somebody point me to a resource on opamp circuit design?

Thanks so much!
Rabs
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