Computer controlled mixer (Home audio)

[henninggs]

Hi

I need some advice/guidance/thoughts.

I'm building my new home. In each room I'll have a set of speakers. Each set of speaker should be able to play 1 or more of 4 sound sources individually mixed.
Let's say I'm listening to the radio (source 1) in room 1 and my wife is listening to a cd (source 2) in room 2. Now the "house-computer" wants our attention witch it will do by sending a soft ping (source 3) to all speakers in the house.
If I move to the bathroom, I'll need the house-computer to turn on the radio in the bathroom too.

So basically I need a computer controlled mixer that takes 4 inputs, mix those inputs and send the signal to one or more outputs.
This is a drawing of what I need: (Just for 2 rooms)


The volume controls should be connected to my computer. Here is my idea:

I'll use the PGA2311 volume control, one for each input, pr. room.
The output from each PGA2311-group will be feed to an amplifier that drives the speakers
The PGA2311 will be controlled by some PIC, the PIC will be controlled by my computer.

Is this doable ?

Your comments are greatly appreciated!

Regards.

[Speedskater]

You will need a recording studio type mixer to combine the 4 volume controls before the signals get to the speaker amplifiers.

[gootee]

You can combine the four line-level volume control output signals with a simple summing amplifier, made with an opamp and some resistors. Go to National Semiconductor | High-performance Analog and search for application notes AN-20 and AN-31. The very simple circuit you need is there. They show a two-input or three-input version but you can just extend it for four inputs.

if you've never built an opamp circuit, before, you will also need a small bi-polar power supply for each room (something like +15v, Gnd, and -15v, for the opamp), and you will need to know that for each of the two power pins on each opamp you must connect a 10 uF electrolytic capacitor in parallel with a 0.1 uF film or ceramic capacitor and connect them from the power pin to the power supply's ground.

Cheers,

Tom

[dangus]

I think it's better to just run ethernet to each room, and use a media player plus amp in each room. The media player/amp console could include an input to use a local iPod or CD player. If space allowed, include a CDROM drive with a controller. I'm not sure what the ideal media player thing would be. It needs networking, LCD display (alphanumeric or graphic), play music and maybe video, possibly recognize people using RFID tags or Bluetooh. Software should be customizable and expandable. The "Chumby" looks promising. [edit] Really really promising; there's plenty of support and even schematics. http://wiki.chumby.com/index.php/Main_Page Maybe there's some network media player that qualifies. For a display, there's 3.5" car headrest LCD monitors for about $30, 7" for $40, or even 17" LCD computer monitors for under $100. (Video could be useful to see who's at the front door, or what the kids are doing.) There's also the Beagleboard, which is well-supported, but that's just a board. Chumby things like the Insignia Infocast are cheaper and include a touch-screen display.

On the other other hand, audio can travel reasonably well over CAT5. Probably even S/PDIF if you can find a cost-effective DAC. Use that CAT5 for ethernet in the future.

[henninggs]

Thanks for your replies.

Originally Posted by gootee

You can combine the four line-level volume control output signals with a simple summing amplifier, made with an opamp and some resistors....

I was wondering how I could combine those 4 signals, you just gave the answer, Thanks gootee!

Originally Posted by dangus

I think it's better to just run ethernet to each room, and use a media player plus amp in each room....

I have been thinking that thought too but I would rather solve my problem with a single box. Also if I for some reason wants to have 2 or more rooms play in sync, it would be hard to do with x numbers of media centers.

Right now, I have a hard time figuring out how I could control a volume IC from my computer. I mentioned the PGA2311+PIC... Another posibility is to use a VCA like the SSM2164 and control that IC whith an analog out board....

How do I do the controlling stuff ?

[gootee]

Can you write software? Or maybe you should find out if someone has used some kind of X-10 module to do a volume control, since there are also wireless computer-control add-ons that can talk to X-10 modules of all sorts (see ebay.com). That way you could also have regular remote controls that you could carry or scatter around, in addition to the computer control.

P.S. You might want to also look into digital potentiometers.

[mdhull]

You really don't need to mix inputs, like CD plus radio, since they're likely to be different and cacophonous when mixed.
Better to use an electronic switching matrix, with all sources at an even level, and then adjust volume on the outputs. The computer audio can be mixed into each output.
I have designed several products using the Analog Devices AD8108 analog crosspoint. It's specified for video, so has a massive bandwidth. This will allow 4 stereo sources to feed 4 stereo destinations



The volume controls indicated can be dual channel digital pots (Microchip MCP4231 - does not remember it's setting on power loss, or MCP4241 - does remember)
The computer audio is mixed in after the output controls, so it's always a constant level.

Regards
Mark

[ronjodu]

A few years back I built a web enabled amp with a "siteplayer to pic to pga to amp". I can access it from anywhere over the web. I'm not all that good at coding but I got most of it working rather well.


FYI SitePlayer - SitePlayer Telnet

[henninggs]

Thanks for your replies. (For some reson I don't get an email when someone replies to this thread so I was unaware of your repiles untill now)

I've do some more research and I'm drawing some schematics. I'll post them here when they are more compleate.

By the way this type of mixer (I think) is called a Matrix Mixer.

[ChrisA]

Originally Posted by henninggs

Hi

I need some advice/guidance/thoughts.

I'm building my new home. In each room I'll have a set of speakers. Each set of speaker should be able to play 1 or more of 4 sound sources individually mixed....

Far to complex. You don't need to build any hardware mixer. Get a USB or Firewire audio interface with one output for each speaker. Connect each output to a small amp and then to the speakers. If two sources need to be mixed you do that inside the computer with software mixer. For physical controls you can use any MIDI control surface, including virtual controllers that run on the iPhone. Then the system is controls by any a a half dozen iPhone apps.

There are any number of controllers available. Or course you couldalways use a mouse bt they would be a major hassle to have to go to the computer. Software controllers look like this example
http://www.saitarasoftware.com/Site/AC-7_Core_Mini.html



As for the home construction details. run speaker wire back to some closet and have it terminate in a big patch panel.