The purpose of the conceptual prototype was to build a device to show potential investors our concept and demonstrate the benefits of using a personal computer to organize and play music or audio. It's hard to explain the benefits of a product that integrates an external soundcard with high quality amplifier modules. It is a lot easier to demonstrate when connected to an HTPC.
Since we have fairly limited funds, it was important to make the prototype with components that wouldn't take a lot of time or cost a fortune to build. So the conceptual prototype is made up of some "off-the-shelf" components. We used a commercial external FireWire based soundcard typically used for professional audio engineering applications and class-D amplifier modules that are available for DIY audio amplifier builders. Since this is a 6 channel system which requires 5 channels of amplification (the 6th channel for the subwoofer or LFE channel does not require amplification because the subwoofers typically are purchased with their own amp), and we want our system to be a modular or flexible system, so we included 3 400W amp modules for the front left, right and center speakers and 2 180W amp modules for the rear left and right speakers. Since the 400W and 180W modules require different operating voltages, we also had to include separate power sections for the front and rear speakers. So we had to have 2 custom toroidal transformers built for the prototype because we couldn't find any stock toroids to meet our needs. Next, we had to add circuitry for converting the AC voltage into the DC voltage needed to power the amp modules and circuitry to limit high in-rush currents during start up. To complete the prototype, we had to build a chassis that could hold everything together in a nice neat package and dissipate any heat generated by the components without generating any noise.
So I now have a box that connects to my HTPC using a FireWire cable and to my Precision Monitor 10 loudspeakers using speaker wire.
Instead of trying to explain the advantages of using a PC to play music, I can now demonstrate that it sounds really good. So during the demonstration they get to hear a really good sounding system and learn a little about the advantages of using a computer for managing your collection and playing music.
It really does sound good. I don't consider myself an "audiophile," but I do appreciate good sound. I've owned a variety of fairly high end esoteric systems in the past, including a pair of Beveridge Model 2 SWs, a modified HQD system, B&W Matrix 801s with an assortment of electronics from Mark Levinson and Audio Research. Not the highest of the high end, but still pretty good sounding stuff. Actually, I had to get rid of the HQD system because it just was too big for my space. My system included a 27" Hartley driver in this huge, heavy subwoofer enclosure that was something like 4'-6" wide x 4'-6" deep x 3'-6" high. The double stacked Quads looked like a pair of big solar panels. It just took up too much space and was far from meeting good GAF or WAF (girlfriend/wife acceptance factor). I really downscaled after the HQD system. Through a series of trades and purchases, I ended up with an upgraded Dynaco ST-70 amp, an Electro Research EK-1 Phono Cartridge/Preamplifier System, Linn Sondek LP-12 turntable and the Precise Monitor 10 loudspeakers. The speakers were probably the weak link in the system (and the amp didn't have a lot of power). However, they were about the same size as the B&W 801s and seemed to have a little more clarity. The tube amp at 35W/channel provided enough power to drive the Monitor 10s, which have a rated efficiency of 88db, to pretty loud listening levels. Anyhow, I was pretty surprised to hear how much better the Monitor 10s sound now that they are hooked up to the class-D amp modules. They are really amazing sounding speakers. I hate to sell them, but could use the cash.
I haven't had as many demonstrations/auditions as I would like, but I've had the opportunity to play the system to a few investors or potential investors, along with a few of my friends and family. Even my wife is impressed and it takes a lot to impress her when it comes to hifi. My Dad, who is a fan of big band music, swing, etc. was very impressed. I played some Frank Sinatra recordings from the 60s and he was amazed. Then I put on a recent Michael Buble' recording and he nearly fell off his seat. Obviously the modern recording took advantage of the latest and greatest studio recording equipment and would naturally sound better than something recorded in 1961.
Now we are working on the "working" prototype. This will be much closer to the actual commercial product. The pro soundcard used in the conceptual prototype has a lot of functionality specifically for recording. Our soundcard component won't need a lot of the recording components, but will need functionality specific to home theater like bass management and digital room correction features. There are also a few options for enhancing the amp modules and power supplies which we will want to include in the working prototype. In future postings, I'll share some more of these details.