cs8416/pcm1798 based project - diyAudio
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Old 4th October 2006, 09:51 PM   #1
cviller is offline cviller  Denmark
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Default cs8416/pcm1798 based project

After some mixed results with pcm1730 I'll try a design with pcm1798. I want to use the Pass D1 IV stage, so the output of pcm1798 should be better suited.

I have finished a draft for the schematics. Comments are very welcome.

I'll make the layout suitable for home etching, but double sided. I already made the other design with cs8416/pcm1730 work, but I think the pcm chip was burned or something, cos it would only play for a couple of hours and then start with a scratching noise. The reset was crab too, so now I'll redo the whole thing with a different chip.

I have left some of the options configurable using jumpers, but marked my choices. I think you'll have a hard time following the nets around those jumpers, but I haven't had time to straighten them out.

What is the best grounding strategy? I'll end up having 2 psu boards, 1 digital and 2 I/V boards. How do I avoid ground loops then?

- Christian
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Old 13th October 2006, 01:21 PM   #2
cviller is offline cviller  Denmark
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Default Jumpers dropped

I decided to drop the jumpers to make the layout easier, but I have left the options available with some easy traces to cut. Any comments on the schematics? I have selected 24bit I2S.
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Old 13th October 2006, 01:32 PM   #3
cviller is offline cviller  Denmark
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Default Layout

I have also finished the layout. I have tried to keep the distances between decoupling capacitors and power pins as short as possible.

The image is a bit broken due to the color exportfeatures in my pcb program.

Green, brown and light red are component side
Light and dark blue and dark red layers are on "solder side"

Is it worth etching?
I hope so.
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Old 13th October 2006, 03:22 PM   #4
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A couple of questions:

Why did you choose the 1798 over the 1792/4?

Would you consider placing the D1 I/V on the same board?

Really nice to see new designs using TI/BB chips!

-David
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Old 13th October 2006, 04:13 PM   #5
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Hello, nice design.
I'm actually working on a project with a STA310 from st. This device has one S/PDIF input. Because of that I wanted to use th CS8416 to "route" several S/PDIF signals to the STA310, so that you can choose your source. Input RXP[0:3]=>Output TX. But when I was working on the schematic I took the datasheet of the CS8416 again to look up something and I read that on page 12 of the pdf document:

"Figure 5 and Figure 6 show the power supply and external connections to the CS8416 when configured for software and hardware modes. Please note that all I/O pins, INCLUDING RXN AND RXP[7:0], OPERATE AT THE VL VOLTAGE."

You said that you used the device already. Did you use the normal input for S/PDIF directly connected as you have it in this schematic or did you make a level convertion? 'Cause as far as I know the level of the S/PDIF signal is about +-0,5V.
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Old 13th October 2006, 05:47 PM   #6
cviller is offline cviller  Denmark
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Thank you for your comments!

Quote:
Originally posted by dw8083
A couple of questions:

Why did you choose the 1798 over the 1792/4?

Would you consider placing the D1 I/V on the same board?

-David

I chose the 98 because I could get those devices, but I think 94 is pin compatible. 92 is controlled with spi/i2c, so I would need a microcontroller.

I like having the D1's separate boards so that I would be able to test other I/V stages, but it would be quite easy to merge them to one board. Or you could just avoid cutting the boards...

Quote:
Originally posted by flybysun
Hello, nice design.
You said that you used the device already. Did you use the normal input for S/PDIF directly connected as you have it in this schematic or did you make a level convertion? 'Cause as far as I know the level of the S/PDIF signal is about +-0,5V.
I have used the input circuits shown on page 55. The signal is AC-coupled, so the operating point should not be a problem. On page 7 the input characteristics are stated and as I understand it, the S/PDIF swings should be enough.

I'll order the rest of the components this weekend and maybe etch the board in the beginning of next week.
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Old 13th October 2006, 07:52 PM   #7
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It should be fine. I just finished my own CS8416/AD1896/PCM1794(8) board about a week ago, and I'm using a pulse transformer for the SPDIF input without a buffer. Let us know how it goes Christian.
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Old 13th October 2006, 08:48 PM   #8
cviller is offline cviller  Denmark
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Yes, it should be fine. It worked before, but with the 1730 chip, which I hope just fried or something.
My biggest concern is actually how to remove the cs8416 from the old board - should I use the hot air gun on the backside or on the component side of the pcb...
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Old 13th October 2006, 08:51 PM   #9
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Ok thanks for the answers,
I don't know maybe I save this chips for some other project and select the input with some mechanical part like a relais or so. The S/PDIF receiver is worth more then signal routing I would say. But I have some basic question: What is a D1 I/V you are using the pcb for?
Cheers
Holger
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Old 13th October 2006, 09:04 PM   #10
cviller is offline cviller  Denmark
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Quote:
Originally posted by flybysun
Ok thanks for the answers,
I don't know maybe I save this chips for some other project and select the input with some mechanical part like a relais or so. The S/PDIF receiver is worth more then signal routing I would say. But I have some basic question: What is a D1 I/V you are using the pcb for?
Cheers
Holger
If you just make proper termination of the S/PDIF signals I'm quite sure you could get away with some sort of mechanical switch between the inputs.

The D1 I/V section is designed by Nelson Pass. You can look through the Pass Labs forum for more information. I found the thread by Promitheus very informative. The stage sounded so unbelievably good that I can't rest before I make this work.
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