32x32 switchable audio matrix

[AndyJott]

Hello,

my vision is to create a 32x32 digitally controllable audio matrix. I already created a very basic functional concept based on the AD75019. But the IC in fact doesn't matter for now as it's still exchangable in my plans. Because I already own 4 AD75019 i've choosen them to create my first basic schematic. As I am only a software engineer with some basic knowledge in electronics I wanted you to have a look over this and tell me if its complete bullshit or perhaps ( I hope so ) a good base to start.

As I read at http://www.midibox.org/dokuwiki/doku.php?id=midibox_audiomatrix I think the biggest problems which can occur is the mighty crosstalk problem (where the MT8816 should fit better than the AD75019) and possible gain problems when routing 1:n or n:1 . I read that even n:1 would make bigger problems than 1:n . If I understood it right, when making 1:n, it would solve the problems if I just add some buffer opamps after the matrix outputs. When I wanted n:1 I need something like a mixer style schematic running through the matrix IC. This would mean I have to add some resistors before the input of the matrix ic. In common to the 1:n option I also have to add an buffer opamp at the outputs of the matrix IC. To be able to chain multiple matrix ICs I also added some buffers before the inputs to be able to distribute the incoming signals to multiple ICs. Additional to that I added resistors and a final output buffer stage to merge the outputs of multiple matrix ICs.

I don't know what would happen when making n:m connections. Should this be prohibited or is it possible without side effects ?

Is this a reasonable idea or isn't it good to chain opamps ? Simplyfied it's nothng more than 2 opamp mixer units chained through the matrix ics. Will the audio quality suffer from this ?

To keep it scalable I'd split boards into 3 types (without the controlling board and other stuff around).... 'input (distribution) stage', 'chainable matrix boards', 'output stage'.

I hope you were able to understand my idea in this :)

 

Best regards,

Andreas

32x32 audio matrix 01.pdf

Edited October 8, 2015 by AndyJott

[AndyJott]

k, just found this thread .... have to read through it :) http://midibox.org/forums/topic/10490-diy-audio-patchbay-with-digital-routinghow-hard

[novski]

Hi Andreas

Thats a big thing you are planing! I like people who think big! 

May you provide some less detailed descriptions about the why you whant to develop such a Matrix/Mixer and what signals you whant to switch?

For me its not clear what you mean to do with 2x 16x16 MX Chip. Is that for stereo analog audio?

Regards, Novski

[Zam]

Hi

Not to discourage you at all, but maybe have a look at second hand audio router like vikinx.

I believe they already have midi control option in addition with Ethernet and RS232.

So as a software guy maybe you can take that route and dev a nice mios32 tool app remote for this.

Just an idea !

Best

Zam

[AndyJott]

Hi Andreas

Thats a big thing you are planing! I like people who think big! 

May you provide some less detailed descriptions about the why you whant to develop such a Matrix/Mixer and what signals you whant to switch?

For me its not clear what you mean to do with 2x 16x16 MX Chip. Is that for stereo analog audio?

Regards, Novski

I want to switch audio signals in my home studio. I am searching a solution where I can handle more than 16 ins/outs while still staying flexible all the time. Most affordable audio interfaces have a maximum of 16 input channels. Usually this are 8 out-of-the-box and 8 additional ones per ADAT extension or s.th. like that. Today I would be satisfied with 16 ins, because I have not so much external gear that the number of 16 need inputs gets exceeded. But for sure in the future there will be the one or other more gear which need to fit into my setup. With a 32x32 matrix switch I would stay very flexible to a) virtually connect only the devices I actually need in a project to the given 16 ins, b) share channels if it suits the situation, c) not have the need to (dis)connect cables and d) save the virtual wiring configuration for my projects.

You told about 2*16x16 .... it's actually 4*16x16 as the needed matrix ic's count will exponentially rise to the channels you want. It shouldn't matter if there are mono or stereo signals as long as the routing gets configured as needed. For example I have a Mutable Instruments Shruti which actually is mono and on the other hand a Virus TI with 6 independant channels.

Hi

Not to discourage you at all, but maybe have a look at second hand audio router like vikinx.

I believe they already have midi control option in addition with Ethernet and RS232.

So as a software guy maybe you can take that route and dev a nice mios32 tool app remote for this.

Just an idea !

Best

Zam

I'd feel better if I can build that device on my own, not only because I think it gets a bit cheaper. As I said I already own 4 AD75019. Opamps arent that expensive and sockets are cheap to buy in china (aliexpress.com) . On the other hand ... selfmade gear is just cooler if it doesn't lack power in comparison to 'professional' gear.

 

Sadly I still don't know if this project 'makes sense', because I have no doubt if the audio quality will suffer from the signal chain. But I can't imagine that it actually would do that much, because it isn't more than simply an input buffer and a mixer circuit with the matrix switch ic in the middle of them. If anybody could answer this question I'd finish the details of the schematics and create the board layouts.

Edited October 11, 2015 by AndyJott

[ilmenator]

Check the data sheets and answer that question yourself!

After spending quite some time thinking about a DIY audio matrix I ended up buying analog patchbays. Probably my best studio purchase in the last couple of years...

[Zam]

Sadly I still don't know if this project 'makes sense', because I have no doubt if the audio quality will suffer from the signal chain. But I can't imagine that it actually would do that much, because it isn't more than simply an input buffer and a mixer circuit with the matrix switch ic in the middle of them. If anybody could answer this question I'd finish the details of the schematics and create the board layouts.

As ilmenaor say, best route for "music" studio is patch bay and cable, I never see any studio with active patchbay/router.

Active patchbay aka matrix or audio router are only used in TV and broadcast (like the vikinx I quote), where audio fidelity come after ultra speed workflow and flexibility.

Best

Zam

[AndyJott]

hmmm. then I think will start with an analog patchbay for now. Thanks for your help !

[novski]

Hi Andy

I installed several Patchbay variants in different studios and i wold recomend you a Neutrik TT Bantam Patch. There are different types availabe on market, but also a one with default connections. It connects the most needed in to out without cables. You can then ether Y a signal or detatch it by sticking a cable in a Uper or lower hole and link it to someware else.

And that for 48 signals on 1RU. Magic...

regards, Ivan

[Antichambre]

Hi,

In broadcast systems we use Guielmetti audio patch, bantam contact is not fine enough for digital signals like AES or S/P DIF.
We use CSF 2x48 in general but ASF model some time is enough for both analog and digital.
I've got 2 CSF 2x48 in my homestudio, there are associated with some krone wiring module which permit to change the position of a machine without soldering on the patch.

regards

[novski]

True! The Neutrik Bantam aren't 110 Ohm AES Compliant! But for cables below 20m there are no problems to expect.

[Antichambre]

You're right too!