Cheap 24/96 DAC, Revision B. - diyAudio
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Old 25th November 2002, 12:59 AM   #1
jwb is offline jwb  United States
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Default Cheap 24/96 DAC, Revision B.

After my experience building and listening to this DAC, I have made some modifications. I included the missing trace, moved some pads that were confusingly symmetrical, and redrawn the transformer at the correct size.

Those are the changes intended for the poor guy building the circuit. The changes for the poor guy <em>listening</em> to the circuit are the separate ground planes. There is one ground plane for the connector and transformer primary, and another "drawbridge" plane for the rest of the circuits. This should cut down on the slight hash imposed on the analog outputs. The builder has the option to power the digital and analog sides from completely separate supplies all the way back to the power transformer.
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Old 15th March 2003, 06:38 PM   #2
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Default Manufacturing information

By demand from two members of this forum, I have prepared the manufacturing information for this board. The attached zip file contains Gerber files for the top, bottom, and both sides' solder masks as well as the Excellon drill file. The zip is suitable for sending to PCB Express, and of course the solder masks can be omitted to save cost.

Cheers,
jwb
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Old 15th March 2003, 06:46 PM   #3
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In case you need the Bill of Materials, it is here:

http://atari.saturn5.com/~jwb/43122-bom.html

Also the schematic is here:

http://atari.saturn5.com/~jwb/43122.png
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Old 17th March 2003, 05:28 AM   #4
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Nice work. What is the output level of the circuit? You did say it was a passive I/V design right?

Stu
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Old 17th March 2003, 06:40 AM   #5
jwb is offline jwb  United States
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The CS43122 has a voltage output; no I/V converter is used. The crowd of transistors right of the DAC is just a fancy, low-noise line driver.

The output level is the same as quoted in CS43122 data sheet.
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Old 17th March 2003, 07:43 AM   #6
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Very nice!
What is the size of the board?

regards - kasra
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Old 17th March 2003, 02:34 PM   #7
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I must have confused your design with someone elses. I still might build one sometime. Thanks for your work . I thought all high end DACs had current output. It's been awhile since I looked at the CS43122 datasheet!

Stu
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Old 27th March 2003, 10:21 PM   #8
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Default Newbie questions

I've never built a DAC before, and I'm thinking of trying this one. But I have some newbie questions:
How do I connect the power supply to this? It says different supplies can be used for the digital and analog portions, but I'm not sure where the digital ends and the analog begins. Also, how much filtering does the power supply need (and is it the same for both the digital and analog parts)? Is a 10V regulated wall-wart sufficient? Additionally, how do I connect the audio outputs and digital input? How can I have multiple input connectors (i.e. coax, optical)? How do I connect SPDIF?
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Old 27th March 2003, 11:04 PM   #9
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There is a Molex connector at the top of the image. This is the +/gnd/- supply for the analog section. There are two vias on the left of the image, these are the +/gnd supply for the digital section. The two vias at the bottom of the board are the +/gnd supply for the clock and input filter. There may be some advantage to separating this from the digital supply.

If you want to use a wall wart, you will need one with +10V, -10V, and GND. Also you will need a <b>regulated</b> wall wart. Otherwise you will get 60Hz noise on the analog output.

The analog outputs are the four vias in a vertical row on the upper right of the image. There are positive and inverted outputs for left and right. I forget which is which; check the datasheet for the CS43122. The outputs need to be AC-coupled using 4.7&micro;F or bigger film capacitors, and tied to ground with some value of resistor.

If you don't want balanced output, obviously you can simply leave the inverted outputs unattached.

The input connector in this design is a 75&Omega; BNC. If you want optical you would need to modify the design. If you want both optical and coaxial, you will need some extra control circuitry.

Cheers,
jwb
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Old 27th March 2003, 11:11 PM   #10
Prune is offline Prune  Canada
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Thanks a lot.
I'm also terribly sorry for the multiple posts, but until now none of my posts were showing up even if I refreshed the page, so I tried posting several times. If a moderator would please delete the reduntant posts...
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