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[web/gag.com] / electronics / audio / wholehouse / index.mdwn

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 # Whole House Audio System
 
 We're designing a completely open hardware and open source solution for
-whole-house audio distribution.
-
-The key hardware component is a board containing a USB audio interface
-and stereo 50 watt class-D audio amplifier.  A set of these boards, one per
-"zone", get wired to speakers in the various rooms.  A Linux system runs
-software that controls audio stream sources, maps them to the various zones, 
-and volume controls the zones .. all controllable from a web browser or 
-Android application.
+whole-house audio distribution.  The intent is sufficient audio quality
+to support a pleasing background music experience around the house... not 
+to be an audiophile-level system.
+
+## Motivation
+
+The system proposed by our builder was hideously proprietary, and apparently
+violated the GPL.  Just couldn't do it...
+
+## System Design
+
+Our builder had a sub-contractor install ceiling-mounted speakers in each
+of 9 zones in our house.  Each zone has a local impedance-balancing volume
+control to allow for local / emergency "turn it down" capability.  There's
+a wire bundle from each zone to the central mechanical room consisting of
+4 conductors for the stereo audio, and 4 twisted pairs (ala CAT-6) we don't
+intend to use immediately.
+
+The new hardware component Bdale designed is a board containing a USB audio 
+interface and stereo class-D audio amplifier.  The USB audio DAC part was
+designed by Burr-Brown and is now a Texas Instruments part.  The class D
+amplifier is also a TI part, available in 15, 30, or 50 watts per 
+channel.  While the PCB layout can handle any of these parts, the 50 watt
+per channel part needs additional heat-sinking and we just don't need that
+much power.  So we built the system using the 30 watt per channel parts.  The
+circuit board is 2.75 x 1.25 inches and less than an inch thick fully 
+populated.
+
+<a href="usbclassd-v0.1.jpg"> <img src="usbclassd-v0.1-thumb.jpg"></a>
+
+A set of these boards, one per
+"zone", each attach to the speaker wires, a DC power supply, and a USB hub
+that is attached to a Debian system in the mech room.  
+
+The Debian (Linux) 
+system runs software that controls audio stream sources, maps them to the 
+various zones, and volume controls the zones .. all controllable from a web 
+browser or Android application.
 
 More details will be posted soon!