[SnoopyRocks]

http://www.national.com/an/AN/AN-779.pdf
http://www.circuitsage.com/filter.html

These should get you started.

 

[Clutz]

I just thought I'd take a stroll through the thread and say "Hey, what's up fella's?"

So, hey- what's up fellas? Feeling good? How's life? Any progress to report?

 

[ble0t]

I've got the filter changes (balanced output section) as well as a couple of other corrections made. I've also been doing some cleanup here and there. 00940 is out of town until next week and I'm waiting to run the updates by him as well as some others to see what they think before I post another update.

Don't worry...I want to see a proto board as bad as you do, but we also want to make sure the design is as optimized as possible

PS - Thanks to Snoopy for the input on the filters

 

[Clutz]

I fully agree - optimize the design as much as possible before going to proto. I was just curious as to how things were going!

Cheers,
Clutz

 

[MegaMeee]

I too thought this thread was in serious need of a bumping...

BTW life's great, Uni sucks and I'm just packing up to go on on hols with the family for Easter.

 

[ezkcdude]

Can AD1794 be used (instead of 98) without any modifications to the schematic?

 

[ble0t]

Quote:

Originally Posted by ezkcdude Can AD1794 be used (instead of 98) without any modifications to the schematic?

I'm going to assume you mean the PCM1794, and the answer is yes, it is pin compatible and can be used in place of the PCM1798.

 

[Clutz]

Quote:

Originally Posted by ezkcdude Can AD1794 be used (instead of 98) without any modifications to the schematic?

It's a PCM1794, it is pin compatible just like ble0t said. In fact it is exactly what I plan on using. I think it's false economy to use the PCM1798 over the 1794 to save $8, when that's a very small fraction of the total cost of putting this DAC together in the end and it's specs are significantly better. That said, there are some very high end CDPs that are using the PCM1732 which isn't as good as the 1798 on paper.

 

[ezkcdude]

Thanks, for correcting me (I must have been drunk when I wrote that). I'm interested because I would like to design a similar DAC, except it would be for a SqueezeBox, so I would replace the USB receiver with a CS8416 to receive SPDIF. The SqueezeBox outputs 16/44.1(48) for FLAC/WAV files at 100% volume, and 24/44.1(48) for all other formats (e.g. mp3) and when attenuating with the digital volume control. I've asked this over at diyaudio but never got a satisfying answer. According to the 1794 spec sheet, you can use an external digital filter, therefore, bypassing the internal one. I think it is best to avoid any additional digital filtering altogether (after the ASRC), and only use analog I/V filtering. If I do HAVE to use the 1974 filter, I would use the slow rolloff mode. Any thought/opinions about this are welcomed.


Edit: Oops! Man, this is a long thread. I just read back starting on page 12, and realized you do plan on using CS8416. Great! I will stay tuned.

 

[00940]

I'm back

ezkcdude : You can only bypass the internal digital filter if you use the pcm1794 in mono mode (p.17 of the datasheet). Using two pcm1794-8 and the following I/V would drive the cost up significantly and it's not considered in the frame of this project.

re: the pcm1794 instead of the pcm1798. The output current of the pcm1794 is twice the output of the pcm1798. You will have to adapt the I/V resistors and the paralleled filter's caps.

 

[ezkcdude]

Quote:

Originally Posted by 00940 ezkcdude : You can only bypass the internal digital filter if you use the pcm1794 in mono mode (p.17 of the datasheet). Using two pcm1794-8 and the following I/V would drive the cost up significantly and it's not considered in the frame of this project.

Thanks! I guess slow rolloff mode will have to do. Is that what you guys are planning?

 

[00940]

for now, it's set in sharp roll off. Reason is simply ease of layout, the CHSL pin is very isolated...

 

[Clutz]

Quote:

Originally Posted by 00940 I'm back ezkcdude : You can only bypass the internal digital filter if you use the pcm1794 in mono mode (p.17 of the datasheet). Using two pcm1794-8 and the following I/V would drive the cost up significantly and it's not considered in the frame of this project. re: the pcm1794 instead of the pcm1798. The output current of the pcm1794 is twice the output of the pcm1798. You will have to adapt the I/V resistors and the paralleled filter's caps.

Nice to see you back 00940!

I'm planning on using the PCM1794 instead of the 1798, so I guess I'll have to change the I/V resistors. Paralleling the filter's caps isn't too big a deal.

 

[MegaMeee]

yep i'll be using the 1794 as well I think...

 

[steinchen]

same here