Both mentioned above transports do that, but I chose the second one (its name is Tango, ARM-based). As from the very beginning, using of HDD as drives was considered (USB-flash maybe more convenient, but today are
still more expensive), the were not a problem with the files size, and therefore I can live without flрё. But support of the high resolution formats, up to 24/94 is great. 2 clock generators must be provided, in
order to have two frequency scales - "normal" scale (44.1 and 88.2 ) and the "computer" scale (48 and 96).
So transport was selected. And is was decided it will be not only transport, but the full audio player, with its own DAC inside. But there is a problem with the control - in the reference design a small LCD with I2C
bus was used, which I do not have and which view I do not like. Or RS232C can be used, with computer (through the terminal software, like Hyper Terminal, Tera Term, etc.). IR remote control works only with Philips
RC5 protocol. (A long time ago I developed an universal software, to work with IR RC several standards, that can learn a command from any remote control unit, working in one of the 5 standards, ported to some
As a result, I did not used Tango's own controls and made my control unit instead. Based on TI's MSP430 microcontroller, this unit provide information on a large format LCD display - 4 lines of 40 characters. Can
learn the commands from any remote control unit, working according to RC5, NEC, Panasonic, Sony (sirc) or Samsung protocol. 6 buttons for the direct control from the front panel were implemented:
- STOP-Directory Out-On/Off
- Play-Directory In
- Rev-Previous Track
- FF-Next Track
- Previous Directory
- Next Directory
In Play Mode, LCD display have information about the track number, track time, track quantity in the current directory, directory and track names, also the current track information (bits, sample rate). The special
technology was used to show the big digits on this type of LCD.
LCD in Play Mode:
LCD in Navigation Mode:
Storage Device (Disc-on-Key/HDD) must be in FAT32 format. Not only WAV file are supported, also CUE (with one or separate WAV).
As you can see at the block diagram, device consists of the following parts:
- Tango - USB Transport, RS232 controlled
- DAC (Analog Devices AD1853 based)
- Low Jitter Double Frequency Clock Generator
- Control Unit (with LCD, Remote Control and front panel buttons)
- Source/Path Switch
- Power Supply
Notice a lot of transformers in the Power Supply! Yes, total separation of power - is "must have" for an excellent sound quality. The
biggest transformer in the right bottom, is for HDD and Tango. One transformer power the Clock Generator. One transformer is
for a DAC's digital VCC, one is for DACs analog VCC, one is for DACs output filter/buffer.
It is now shown on this photo, but there is another small transformer, who power the Control Unit. This transformer is on duty, it
works all the time. When the power button was pressed on the Remote Control Unit (or front panel button), the Control Unit switches on all other transformers.
As HDD I used 1T 3.5" Western Digital Caviar Green 1TB IntelliPower WD10EARS drive. It is cold and quiet. By the way, with this
HDD, dedicated power supply can be reduced. What you see on the picture - was used during experiments with HDD with much higher current consumption.
Source/Path switch (small yellow prototype board on the right top) is intended to switch storage device between the internal HDD and external USB Disc-On-Key. Notice 2 connectors under the display:
Left USB-A connector - is for Disc-On-Key, right mini USB - is to connect computer. In the last case, the internal HDD is
disconnected from the player, and operate like external drive. This is for easy managing audio files on this HDD without opening the player.
It is prototype board used for Source/Path Switch, later this was changed to the normal 2 layers PCB. Also USB/SATA convertor was located on this PCB.
Source/Path Switch block diagram:
This device is totally home made. Standard 19 2U case was used, only its front panel was replaced. As I dont have a heavy
equipment for metal processing at home, front panel was made from wood. For wood I have some tools, even the router and the
router table (also home made) and air compressor for painting, thanks to my loudspeaker design practice.
Front Panel was made from a plywood:
After the routing, it was covered with veneer, painted and lacquered.
Front panel buttons were also made with the same technology:
You see 3 parts, operates as 6 buttons - these parts were mounted on a axis at the PCB peace. There are 6 pushbutton switches under these parts.
Maybe this player does not looks like industrial made, but its sound is excellent. Of course, I will not stop to develop another
versions, this model can substitute CD-Player, but I still need DVD-Audio Player to listen 24/192 format, and 24/96 5.1 multichannel. Also I have some ideas of another control and topology.
What I need is to say thanks to Tangos author, and everybody who took part in this player development, by his help, advice, component purchasing, listening, etc.