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powerpan 15th May 2011 03:45 AM

DIY hifi source
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starting a DIY project for HIFI source, supports most lossless compression expect WMA lossless. up to 192K 24 bit output. (higher output not tested yet)

hardware specifications:
up to 456M ARM926
128MB DDR2
USB 2.0 DUAL ROLE (could use as USB sound card, not fully tested yet)
USB 1.1 host
SDHCx2 one for filesystem on cpu board one for customer usage
10/100M cable network
usb serial converter included

plug-in codec supported
open source except control parts and cpu board schematic. interface by QT and could control by PC/PDA/network equipment via network.

there will be different configuration in digital part like 8805/FPGA clock module as i2s clock generator (FPGA with OCXO proved to provide the best sound in test), and WIFI is optional (under test now)

we designed this first by a part time team since 2008 and now wanna make it a DIY kit. there are lots of things to do, anybody interest in this or wanna join into this project, please drop a message.

need help on DAC part.

to do:
air play(with USB wifi ZD1211B first)
digital signal processing by DSP by upgrading cpu with DSP included
multi-channel output
digital input to digital output re-clocking to local OSC (it means after reclock, the clock will be the same as local OSC), no need 2nd PLL
GUI rewrite by simple cross platform support like SDL. (for lower cpu time and faster responds, much smaller in size)

SoNic_real_one 15th May 2011 02:29 PM


Originally Posted by powerpan (
digital input to digital output re-clocking to local OSC (it means after reclock, the clock will be the same as local OSC), no need 2nd PLL

That is tricky to do RIGHT. To make use of the DSP, I would use a FIFO buffer in the internal RAM (usually is dual port) to keep at least 5-10 seconds worth of data. Reset the pointer in the silence pause.

I would employ also a Over Sampling in the DSP. This OS needs to be done right, by interpolating the intermediate values (maybe dithering but that is more complex to do), not by simply repeating the sample. That means that the 16 bit signals will be converted to 24 bit (to allow headroom).

Because there are open sources for HDCD decoding around, I would add that to the capabilities. FLAC format.
DSD in .DFF format would be nice to have too. Decoding sources are also available.

DAC - I would go for one that doesn't have internal OS, in order to fully benefit of the DSP OS. There are a bunch of DAC's that have internal OS and claim better numbers, but I think a proper done external filter/OS (DSP) will "beat" them acoustically.

PCM1704U accepts at the input a 768kHz samplerate signal. That is enough for 4X of 176.4/192kHz, 8X of 88.2/96kHz and 16x of 44.1/48kHz. The bad thing about this DAC is that it gets expensive on the OpAmp side - recomended are OPA627 for I/V and OPA2134 for filter. Ideally it would to be "K" grade part. And is one per channel.

If cost is an issue, a multichannel DAC with voltage outputs will do a lot for lowering the cost. That means, sadly, that most of the OS/filtering will be done by DAC... sure, you can still go 4x for 44.1/48kHz and 2x for 88.2/96kHz in the DSP and apply dithering/interpolation for 16 bit.
ES9018 might be a good choise.

powerpan 16th May 2011 05:03 AM

HDCD is MS license, I have the decoder but don't wanna to release with the board.
DSD's output is not supported by i2s, ignore it.
and I don't think DSD sounds better, just kinda sigma-delta ADC data, like 120K sampling rate something compare with original ADC method.

I'm not making the whole machine, just the board with simple DAC, for DIYers only. target price under USB100.

I have all the DSP filters on hand but need time to port it.

wangxianok 17th May 2011 02:31 PM

good choice,i am look for a digital-player for several years.

too many compact discs make me headache...also the CD player' life is limited.

if you can develop a whole function software and a friendly interface,i think it will spark a revolution for the HI-FI.

we can use is as a high performance digital source,
an USB sound card,
a digital equalizer,
a digital dividing networks for loudspeaker systems
expecting to this board!

powerpan 17th May 2011 02:40 PM

supported lossless format:
APE --- could use monkey's audio but license needed
ALAC (apple lossless)

other format:

braveqian 18th May 2011 01:44 AM

expecting to this new high performance digital source

ARMik 18th May 2011 04:24 AM


Originally Posted by powerpan (
I'm not making the whole machine, just the board with simple DAC, for DIYers only. target price under USB100.

That in goes in these USB100?

powerpan 20th May 2011 04:57 PM


Originally Posted by ARMik (
That in goes in these USB100?

US$ 100 for the board with i2s out and s/pdif in/out, will include an AD1955 as DAC. this is the basic version with WM8805 as the clock generator.
FPGA clock source will be later, and will be pure digital output without ADC

wangxianok 26th May 2011 09:14 AM

will u provide a display module,also the basic UI for the software?

powerpan 1st June 2011 02:55 PM

current display UI is 1.77" 160x128 for car audio is good, and later will make it bigger like 320x240 with touch panel.

all interface are open for user modify.

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