Beta Scratch Build

Introduction

Tail end of 2012 I built a small HTPC, Mini-ITX based with a [not very well done] hand crafted case.
Sadly in operation, this lasted about a week before the PICO PSU failed - probably due to over heating caused by bottom air vent being blocked.
So, in spring, I resurrected the hardware, added internal 15W stereo amp unit and built a new case.

Components

MSI H61I-E35 Motherboard (min-itx unit)
Intel Pentium G860 3.0GHz
Akasa AK-CC7118HP01 K25 Low Profile Intel Cooler
OZC 60G SDD
4G generic
PICO 12V PSU
Yoga USB sound adaptor
2 x 15W Class D 12V amp based on TA2024

Case

Chassis - old Dell desk top unit
Skin - reclaimed oak floor board

OS + Software

Windows 7 64Bit
MediaPortal 1.4 Final
Modified FlowGold Theme
MPTVSeries
MovingPictures

Pictures

Front - the illuminated section is strip of white LED with green filter - was red but looked too much like offspring of a mismatched mating of the Eye of Sauron & Kitt from Knight Rider.
 

 
Back - shows the donor PC chassis.  The 60cm fan mount is from the original PSU.
 

 
Motherboard - the USB 5.1 audio interface is connected to the MB USD header, with a simple converter.
 

 
PICO PSU - very unit, external 150W 12V power brick, supplies the PC & amp.
 

 
AMP - small D class 15W unit.
 

 
 

Design Consideration

Internal Amp.   Previous clients have output either direct to external amp and more recently via HDMI.  
Both had issues, turning off the TV didn't stop live TV or video sound, and needed TV on for music using HDMI.  
As I had a pair of small Denon bookshelf speakers sitting idle, using a dedicated internal amp seemed sensible.  While the performance of the amp in terms of distortion is not good at higher levels, the speaker efficiency and small room mean it operates only at low levels - max output is capped at 35% and I had to update the volume settings with a custom scale to allow a wider dynamic range.
One issue in using this specific unit, on the HTPC back panel, the phono sockets I'm using to connect the amp to speakers was to be built with common earth via chassis.  Fortunately, before I completed the wiring I checked the circuit diagram - the speaker outputs are no common earth - with the protection built into design, suspect it would simply have not worked, but I don't want to test it:->

 

Size

Based on components.  The width set by donor chassis, the height by on board USB header connector and depth, just enough to accommodate the parts and allow a little air flow.

Performance

Even with internal amp and single 60cm fan venting out [does make a little noisy in a quiet room but totally un-noticed in normal operation], running 24x7 in a warm room, idle or busy, temperature varies little, with CPU around 40 and system between 35 and 50 [50 only when the XBox that sits on top of it is active].
Operating performance, fine, even though this is low spec CPU, no problems noted.

Issues

Click suppression on the amp/speakers on power on AND the OS starting - lacks finesse.

Overall

Modest hardware, great fun in building it [if you like angle grinders and sparks that is], modest looks [still not happy with case overall, but step up from the alpha.  Build in amp was more a whim than a well planned decision, I think I was very lucky in the selected unit in terms of power, performance and audio quality.
As I'm using recycled parts for case, it's quite cost effective - unless you count time & effort; 

Final Version

Still in planning, but looking at Haswell based unit, double decker build [so I can replace amp with 3 channel unit, install 4 port ethernet switch and move from NAS to internal drives] based on a couple of 1U reclaimed switch/router chassis I have.  System illumination built into deck separators [acrylic light path], no external switch [experimenting with capacitive touch sensors] and Arduino controller for power & speaker sequencing to avoid power surges.