DIY Audio Router

bubba_b

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I've looked and looked 'til my head hurt and I can't find what I'm looking for. I would like to build a simple 4 input/4 output signal router. I wanna take 4 different audio sources (CD1, CD2, computer, tape, etc.) and be able to route any or all of them to any or all of 4 different outputs (computer, mastering deck, monitors, etc.). Anyone help with this, maybe point me to a schematic that's even close? Thanks. :grin:
 

enthalpystudios

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are sources mono or stereo? balanced or unbalanced?

I'm working on something similar, but still haven't got all my needs sorted out, as I have more features than that to implement. But for a basic in/out box, you can do that with rotary switches. Two of 'em. And i/o connectors and wires.

It's simple, but I'm new to this stuff too, so I could be wrong. I can go more in depth, but things get a bit different depending on if your sources/destinations are mono/stereo balanced/unbalanced.

I can post a picture to illustrate what I mean, and perhaps someone who's totally sure can dbl check it for me.

Billy
 

soundguy

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if you dont need the thing on a rotary switch, dont overlook how easy it would be to do what you need with a half normalled patch bay.

dave
 

enthalpystudios

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for more than 3 stereo balanced sources, you'll want a switch like this

http://www.mouser.com/index.cfm?han...uctid=777370&e_categoryid=144&e_pcodeid=01019

You'll have to put in stops for 4 positions. If you only have 3 ins and 3 outs, if stereo balanced is indeed the case, you can use lorlins, which have a stop installed. Those 2-deck alphas in the link above need little tiny screws screwed in as stops, otherwise they'll click around and around and..... you get the point.

I just finished my 'real job tasks,' i'll make something in corel that should illustrate my point, and maybe someone can verify that i'm correct.

billy
 

enthalpystudios

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posted at the same time, but very good point dave. 2 patch cables is all you'll need if using anything other than your 'normal' connections.

the reason I want to make a 'unit' like this, which may actually not have i/o selection in the end (i change its config every 8 days), is because I want a passive volume control and vu meters on my monitor outs. Probably a buffered feed for a headphone amp as well. But like I said, my configuration changes all the time, thats why i'm still putting it off until I finish installing my patchbays, as I may need (or not need) different features.

billy
 

NewYorkDave

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4x4 audio crosspoint switch (aka "matrix"). Your router could be made from a chip and a few supporting components. This is really the "right" way to do an any-input to any-or-all-outputs scenario with appropriate isolation between sources and destinations.
 

bubba_b

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Ok, to sum up most of the questions here:
  • - 3 stereo balanced TRS inputs
    - 1 stereo unbalanced RCA input
    - outputs the same as inputs

NYDave is right on with what I'm looking for (a matrix style router). Using rotary switches, I'd only be able to send one of the 4 ins to one of the 4 outs at a time. Same with a patchbay (thought of that, too). I need to be able to send all four ins to any of all four outs simultaneously.

Ex: send a tape deck(IN1) to a computer soundcard (OUT1) and a CD recorder (OUT2), while also sending a CD player(IN2) to a stereo channel on a mixer (OUT3) and a hard disk recorder (OUT4).

Dave, do you have specifics on the parts I'd need? I've got all the jacks and wire, need switches and the chip(s) you're talking about[/b]
 

NewYorkDave

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I know there's a number of chips out there that'd fit the bill, although you might have trouble finding 'em smaller than 8x8 these days. Another, possibly lower-cost option is to use a bunch of active buffers for the input signals and mechanical switches. It's cumbersome but works. I think Opamp Labs still makes small routers built that way. Another example is the Gentner audio Routing Distribution Amplifier (RDA), a nice older unit that can select any combination of inputs to any output using jumpers. The jumpers are a pain in the ass compared to switches but not too bad if you're not changing your setup all the time, and of course switches could be kludged-in if you're ambitious enough.
 

mobyd

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A chip worth looking at is the Analog Devices AD75019 - it is a 16 X 16 matrix of transmission gates (think 74HC4066) and works just dandy for this sort of application. Costs around $20. I made a few muxes using them for multi room restaraunts accessing a stack of CD stacker players.
Here's my (primitive 1993 home-etch PCB) example of the beast...
mux.JPG

Use the microcontroller of your choice to drive the 3 wire interface.
M
 

Boswell

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The CD input is self-evident, but are the balanced sources high level or low level? Assuming they are high level (otherwise you would not want to switch them around with a CD signal), a good way to do this is to use differential multiplexers (muxes). You can get dual 4-in to 1-out selected by a pair of logic levels, eg Analog Devices ADG409.

What you would need is 4 of these parts. The same numbered inputs of each are connected to the 4 signal sources (+ and -), and the outputs taken through buffers to your 4 outputs. You then need 4 small rotary, push button or even piano-key switches to select the logic inputs for each multiplexer. The buffers could be NE5534, OPA134, OPA607 or similar. Put it together with the ins and outs and a linear +/-15V supply in a case to suit, and you're there!

Deal with the unbalanced source by grounding the -input of the muxes for that channel and not using the -out mux for the unbalanced output.
 

bubba_b

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Thanks, Boswell. I went to Analog Devices site and was able to get 4 of those ADG409's for free (2 free samples of two types). Nice! Otherwise, I'd have to spend $85 for a bag or 25 of them. I'll be trying this out and getting back here when it's all wired up. Thanks, fellas!
 

NewYorkDave

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It looks like I'm too late, but I just sketched this simple routing/mixing matrix:

IOMatrix.png


Individual pushbuttons could be used for the ability to route multiple inputs to a given output (i.e., mixing). Or you could use interlocking pushbuttons (or rotary switches) if you don't want the mixing capability.
 

bubba_b

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That's good, too. I'll try both. Are those NE5534's on the ind. inputs and on the outs?
 

Nanno977

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Mar 6, 2006
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Hi, i was reading and i thought i could ask if someone can help me.

I need something like that but inverse function.
I mean, one input and then shitching to 4 diffrent outputs, would it be possible? does it need to have amp for each output or it can be done using only the amp that the out source already have?

Any suggestions?
Thank you.
 

bubba_b

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Is this a speaker selector switch you're wanting? If you build it with just some jacks, wire and a rotary switch, it's simple, and it doesn't matter which way you use it (IE: a 4in - 1out is also a 1in - 4out, depending on what you plug in where). I've built one of those, but with my simple design, I sometimes have very low crosstalk on the unselected outs.

BTW, what's a simple way to get rid of that (better isolation between channels)?
 

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