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Get familiar with the reaction system: Introducing the Reaction System
Jupiter Station High End Media Playback Deck
I've mentioned it in passing before, but since I'm about to build the beast next week on my vacation, I figure I'll detail the design here. Let me start with the overview and then the block diagram of the overall system.
Simply put, the design is simply a costly HTPC focused on audio performance. The core is a Windows PC, driven by a power adapter fed from a laptop power brick. The audio is converted by an audiophile grade AKM4495 dual mode DAC (one DAC per channel to reduce the noise floor). That output is fed into a Burr Brown PGA2311 preamplifier, which is a single chip stereo analog solution controlled digitally. The controller for this will be an Arduino based board, written by me. Here is the block diagram:
The deck requires an annoying three power supply solution. I avoided using a single R-Core for the DAC and Preamp because I'd rather buy the toroids from AnTek.
If you notice, I've chosen to use a splitter to pull the PCM audio from the HDMI feed rather than use a usb connection. This is a choice I made to make the audio experience more transparent, since any device on the HDMI output end will get the same audio feed that the high end output gets, without having to switch any settings in the windows software.
Two additional RCA, line-level inputs all the preamplifier stage to act as a preamp for other attached devices.
The back panel will offer: 2x USB 3.0, 2x USB 2.0, HDMI, Gigabit Ethernet, Wireless N antenna, RCA analog out, 2x RCA analog in. The nice thing about the USB and analog in, means direct level-matched comparisons between USB external DACs can be easily made.
The whole device will be controllable via a 2.4ghz wireless keyboard/mouse, as well as via webpage using local network and devices such as your phone.
The clincher: If I can get the programming for the arduino right, and rig up a simple quality MIC, the preamp stage will be able to automatically level match for DIY events.
Simply put, the design is simply a costly HTPC focused on audio performance. The core is a Windows PC, driven by a power adapter fed from a laptop power brick. The audio is converted by an audiophile grade AKM4495 dual mode DAC (one DAC per channel to reduce the noise floor). That output is fed into a Burr Brown PGA2311 preamplifier, which is a single chip stereo analog solution controlled digitally. The controller for this will be an Arduino based board, written by me. Here is the block diagram:
The deck requires an annoying three power supply solution. I avoided using a single R-Core for the DAC and Preamp because I'd rather buy the toroids from AnTek.
If you notice, I've chosen to use a splitter to pull the PCM audio from the HDMI feed rather than use a usb connection. This is a choice I made to make the audio experience more transparent, since any device on the HDMI output end will get the same audio feed that the high end output gets, without having to switch any settings in the windows software.
Two additional RCA, line-level inputs all the preamplifier stage to act as a preamp for other attached devices.
The back panel will offer: 2x USB 3.0, 2x USB 2.0, HDMI, Gigabit Ethernet, Wireless N antenna, RCA analog out, 2x RCA analog in. The nice thing about the USB and analog in, means direct level-matched comparisons between USB external DACs can be easily made.
The whole device will be controllable via a 2.4ghz wireless keyboard/mouse, as well as via webpage using local network and devices such as your phone.
The clincher: If I can get the programming for the arduino right, and rig up a simple quality MIC, the preamp stage will be able to automatically level match for DIY events.
= Howard Stark: "This is the key to the future. I'm limited by the technology of my time, but one day you'll figure this out."
Comments
https://www.flickr.com/photos/jasonp75/28978281314
https://www.flickr.com/photos/jasonp75/29523037901
https://www.flickr.com/photos/jasonp75/28978276184
The input transcoder that feeds the AK4495 is the AK4118, known for being a good low jitter solution. The output stage for each channel is one JRC NE5534 opamp in a minimalist design. I think the board is looking good, can't wait to hear and measure it.
If you configure the mic input to use a 3.5mm jack and a dynamic microphone, the calibration mics supplied with the better AVR units will work just fine. In fact, I will donate one I have sitting around. Frequency response is not hyper critical when setting levels - since it is applied equally across all DUT.
Can the mic in be used to control and set the appropriate spl automagically?
Regards
Ani
Ani, the splitter pulls the pcm audio stream out of the HDMI output of the PC. The reason for this approach is to make computer operation simple. If you are watching a YouTube video, the same audio stream going to the tv feeding into the DAC.
There is no audio stream going to the Arduino, it just programs the PGA2311 volume. And yes, with a calibrated Mic on it, we might just have automatic level matching. Which would be awesome.
The dual DAC was harder to find, but I found this design eventually, with a couple mods that the provider was willing to make for me. Researching it looks like yuan jing designed this board, though it isn't listed on their store.
I have all the parts and have started laying out the physical design. It will be two "decks", meaning a two layer design. On the bottom deck/layer will be all the computer components: motherboard, psu, ssd. On the top deck will be all the audio components: DAC board, Preamp Board, Arduino controller, toroids for power. The top deck will have its own power switch, independent of the computer core on the lower deck.
Here is what I've drawn up for the layout (minus wiring guide) in my trusty draw program:
Top Deck:
Bottom Deck:The overall box dimensions will be 18" wide, 12" deep, and a little over 5" tall given the two decks. There is some wasted space in the layout but I don't dare push smaller over concern for ventilation and wiring. If you notice there is a hole between the two decks, allowing the CPU cooler for the motherboard to have enough air space to do its job. The top deck will have its own power switch, so that the core can be operated with or without it on as needed.
Stock Intel Haswell cooler and Antec 120mm True Quiet case fan. All you can hear is me in that video, I couldn't hear them at all from a few inches away. NIce!
All the machining on the panels for the box was completed today. Pics to come this weekend when I glue up the box.
Flickr Album: https://flic.kr/s/aHskEE2L3T
https://www.flickr.com/photos/jasonp75/albums/72157671272685023
https://www.flickr.com/photos/jasonp75/29959909982/
https://www.flickr.com/photos/jasonp75/29511733123
Assembled with the top on.
Now to get it all together, tested and in working order. The fancy cutout on top is for the 120mm silent fan to cool the components. Air flow exits from the small quarter-inch holes on the sides.
I hope to have the start of the distressed metal finish on the birch ply before Iowa!
https://www.flickr.com/photos/jasonp75/29545225874
https://www.flickr.com/photos/jasonp75/30095796042/in/album-72157671272685023/