Archive for April, 2012

New FDA-1B Development History

Monday, April 30th, 2012

Here is the history of the past versions of FDA-1B for past 1.5 years.  I am still searching for the photo of V3 but I believe I did not take any photo of it due to the poorly design of the digital input selection.

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During the development process in V1, many regulators had been tested on the PCM1794A for both the 3.3V and 5V regulators and eventually the simple LM317T plus AMS1117 regulators were selected for it most balance sonic performance.  The lesson learnt here is that expensive and high performance low noise regulator might not sound best in this design.  Also various SMT and Through-hole transistors were tested.  Resistors and capacitors were also tested at various locations to see how much it will affect the sound.  Of course the most important evaluation were the ASRC chips like AD1896, SRC4192 and CS8421.  After many hours of listening, AD1896 with 96k Fs output is rated the best sound ASRC chip in this platform.  For the digital input on the 4th selection – I2S/USB, PCM2707 (USB 16bit 48k) was evaluated but the sound was just too ordinary.  Later XMOS USB reference design was plug into the I2S input and the sound is just too good to be true.  Other receiver chips were evaluated like DIR9001, WM8804, WM8805 and CS8416.  The best sound chip is WM8804, then WM8805, then CS8416 and last is DIR9001.  In fact I would say the WM8804 and XMOS reference design sound equally good in FDA-1B. Thus I have no urgency to move to USB yet as the CD-PRO2 transport and the Logitech Classic media player is providing digital source music with no issue at all in both V13 and V15c versions.

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In the final version V13, it is basically a SMT version mainly designed for mass production.  Then a through-hole (TH) version V15c was created for the DIY market.  So here is why I start to sell the FDA-1B DIY DAC from April 2012.

FDA-1B Rev History – Summary of the revision change history

V1 – Through-Hole version – evaluate regulators, ASRC and 4th digital input + CS8416

V2 – Convert to SMT in digital section + CS8416

V3 – SMT and WM8804 with digital input switch.

V4 – Layout improvement, use relay for digital input select + WM8804

V5 – Layout improvement

V10 – Layout improvement

V13 – Improve I2S bus timing, add SMT pads for IV section; full SMT version for mass production

V15c – DIY version for DIY market