Another PCM1730 based DAC

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cviller

cviller

Member
Joined 2005
Hi Jens,

I'm working on a similar project http://www.diyaudio.com/forums/showthread.php?s=&threadid=79152 , but with cs8416.

I think you might have connected the FMT to 20bit Standard instead of 24bit I2S. Your schematics are so much cleaner than mine. :( It is a really good idea to rearrange the symbol, so related pins are close to each other - maybe I should adopt that.

Have you considered reclocking? I can't decide if I should go for a reclocking and sample rate conversion approach or rely on the recievers pll.
 
JensRasmussen

JensRasmussen

Member
Joined 2002
Hi,

Thanks for your comments.

I have used this setup:
FMT2 = 1
FMT1 = 0
FMT0 = 1

I think this sets I2S 24 bit mode..... I think that this also supports 16 bit mode (Not sure though but it is what Lars did in his DAC).

I will not do any reclocking it my first attempt...maybe second time arround.

If you use eagle I can offer you some of my lib files

\Jens
 
cviller

cviller

Member
Joined 2005
Sorry, you are right! :clown:

Thanks, but I'm not using eagle. I'm an open source kinda guy :cool:, but some times I have to pay by getting used to a crazy GUI. I'm using gschem, and I don't really like it, but the layout part called "pcb" is actually quite good.

Are you making the same psu as lars did?
 
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ezkcdude

Member
Joined 2005
ezdiyaudio.com
Jens, I am also in the process of designing a DAC, which uses CS8416 and PCM1794 (and AD1896 for upsampling). I'm planning to use AD8610's for the I/V stage (I've posted a schematic elsewhere in the forum, which has been slightly changed now but nothing major). Basically, the last thing I need to work out before I start prototyping are the specifics of the regulation. I'm thinking about using LM317/337 adjustable regulators. I'm guessing you will need +/- 12V for the 627's, so proper regulation is important.
 
JensRasmussen

JensRasmussen

Member
Joined 2002
I started this project to find out what it would take to make a nice sounding DAC, if you are further in your project, I might ask you for boards if you get any made....

Why do you want to upsample? is the I2S signal from the S/P dif converter not ok?

Is there something "wrong" with the PCM1730 converter?

\Jens
 
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ezkcdude

Member
Joined 2005
ezdiyaudio.com
JensRasmussen said:
I started this project to find out what it would take to make a nice sounding DAC, if you are further in your project, I might ask you for boards if you get any made....

Why do you want to upsample? is the I2S signal from the S/P dif converter not ok?

Is there something "wrong" with the PCM1730 converter?

\Jens
Click to expand...

You ever heard the expression, "There's more than one way to skin a cat."? There's an infinite way of designing these things, and I've chosen my design "philosophy" based on all the available knowledge. PCM1794 has better specs and higher current output. You can also substitute the cheaper and slightly lower-spec'ed PCM1798 which is pin compatible. As for the AD1896, it really serves two purposes (if you believe the hype, of course): 1) Minimize jitter by asynchronous re-clocking and 2) Upsampling to a higher frequency makes possible the elimination of analog filtering (hence, removal of the second op amp in your design). Now, it should be noted, that these are just my opinions based on what I have read, albeit extensively. There are plenty of people who completely disagree on either or both of those counts. I thought about making my design more simple, but I figured if I'm going to take the time and spend the money to actually do this, which will take a lot of both, I might as well try to "get it right" the first time. I should also mention that I am not definitely not the only one with this design. If you go over to head-fi, you will find a thread about a USB DAC that also uses CS8416/AD1896/PCM1798(4). I don't know what the state of that design is right now. It uses OPA1632 for a balanced I/V stage, and I thought about that for a while, but then decided to go single-ended. That design is also more complicated because it uses a microcontroller (PIC) for the CS8416, which I didn't want to do. (Too hard for me!)
 
C

capslock

Member
Joined 2002
ezkcdude said:


You ever heard the expression, "There's more than one way to skin a cat."? There's an infinite way of designing these things, and I've chosen my design "philosophy" based on all the available knowledge. PCM1794 has better specs and higher current output. You can also substitute the cheaper and slightly lower-spec'ed PCM1798 which is pin compatible. As for the AD1896, it really serves two purposes (if you believe the hype, of course): 1) Minimize jitter by asynchronous re-clocking and 2) Upsampling to a higher frequency makes possible the elimination of analog filtering (hence, removal of the second op amp in your design). Now, it should be noted, that these are just my opinions based on what I have read, albeit extensively. There are plenty of people who completely disagree on either or both of those counts. I thought about making my design more simple, but I figured if I'm going to take the time and spend the money to actually do this, which will take a lot of both, I might as well try to "get it right" the first time. I should also mention that I am not definitely not the only one with this design. If you go over to head-fi, you will find a thread about a USB DAC that also uses CS8416/AD1896/PCM1798(4). I don't know what the state of that design is right now. It uses OPA1632 for a balanced I/V stage, and I thought about that for a while, but then decided to go single-ended. That design is also more complicated because it uses a microcontroller (PIC) for the CS8416, which I didn't want to do. (Too hard for me!)
Click to expand...


Those PCM270x can only output 16 bit / 48 kHz max., right? Also, they appear to Windows as a HIF (human interface) device rather than standard WDM audio, so it will be difficult to use them in an ASIO environment?
 
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