Hello diyers,
This is my first post on this forum, and i want to present you my new DAC.
Ok, it's just another oversampling one, but i want to share this to help peoples who like me, encounter some problems during construction. I had some difficulties to make it working, but now it's quite ok. In advance, sorry for my bad english...
Presentation :
So, after tweaking for sometimes my cheap Sony CDP-XE330 i decided to build this DAC. This is my first one, so when i start the design, i want it too implements only the necessary functions, and to be a littely configurable after the board was done.
The receiver is an AD1892 asynchronous receiver. It's clocked by a PLL1707 at 24.576 Mhz (48kHz upsampling). A PIC microcontroler program the internals registers to choose the format of serial data.
The DAC is an AD1853 which is actually receiving 16bits words. I have planned to use 20bits words but during my first tests, I encountered a problem quite similar as this one :
http://www.diyaudio.com/forums/showthread.php?s=&threadid=19302&highlight=AD1853
but affecting the two channels.. It was less pronounced with 16bits packed mode. Now, i haven't precisely identify the problem (i have a very old scope with low bandwith, no memory), but it was solved by warming one more time all the pins of the CMS chip. 20bits will be tested soon i think
The I/V conversion, is a jocko homo simple implementation which sound really great (even if it's not the secret version ). Thanks for this jocko..
I have some questions about this point to finalize my board :
How to choose the current values ? Actually i have 10mA for the positive rail and 5mA for the negative. When i first test the board, i was using two identical CCS configured at 10mA each, and the sound was completely distorded. Can somebody explain me why ?
Also, i have not installed separated regulators for the two channels (I/V rails), and +15V and -15V are coming from simple power supply (LM317 regul). I was thinking of a simple zener+transistor solution to isolate the lines.. Will it add some noise ? What are the voltage reference more silent ? LED in series ? Some advices are welcome...
Thanks.
This is my first post on this forum, and i want to present you my new DAC.
Ok, it's just another oversampling one, but i want to share this to help peoples who like me, encounter some problems during construction. I had some difficulties to make it working, but now it's quite ok. In advance, sorry for my bad english...
Presentation :
So, after tweaking for sometimes my cheap Sony CDP-XE330 i decided to build this DAC. This is my first one, so when i start the design, i want it too implements only the necessary functions, and to be a littely configurable after the board was done.
The receiver is an AD1892 asynchronous receiver. It's clocked by a PLL1707 at 24.576 Mhz (48kHz upsampling). A PIC microcontroler program the internals registers to choose the format of serial data.
The DAC is an AD1853 which is actually receiving 16bits words. I have planned to use 20bits words but during my first tests, I encountered a problem quite similar as this one :
http://www.diyaudio.com/forums/showthread.php?s=&threadid=19302&highlight=AD1853
but affecting the two channels.. It was less pronounced with 16bits packed mode. Now, i haven't precisely identify the problem (i have a very old scope with low bandwith, no memory), but it was solved by warming one more time all the pins of the CMS chip. 20bits will be tested soon i think
The I/V conversion, is a jocko homo simple implementation which sound really great (even if it's not the secret version
). Thanks for this jocko..I have some questions about this point to finalize my board :
How to choose the current values ? Actually i have 10mA for the positive rail and 5mA for the negative. When i first test the board, i was using two identical CCS configured at 10mA each, and the sound was completely distorded. Can somebody explain me why ?
Also, i have not installed separated regulators for the two channels (I/V rails), and +15V and -15V are coming from simple power supply (LM317 regul). I was thinking of a simple zener+transistor solution to isolate the lines.. Will it add some noise ? What are the voltage reference more silent ? LED in series ? Some advices are welcome...
Thanks.
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