Cheap 24/96 DAC, Revision B.

jwb · 25th November 2002, 12:59 AM

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.

jwb · 15th March 2003, 06:38 PM

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

jwb · 15th March 2003, 06:46 PM

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

maczrool · 17th March 2003, 05:28 AM

Nice work. What is the output level of the circuit? You did say it was a passive I/V design right?

Stu

jwb · 17th March 2003, 06:40 AM

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.

kasra · 17th March 2003, 07:43 AM

Very nice!
What is the size of the board?

regards - kasra

maczrool · 17th March 2003, 02:34 PM

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

Prune · 27th March 2003, 10:21 PM

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?

jwb · 27th March 2003, 11:04 PM

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 4.7µF 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 75Ω 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

Prune · 27th March 2003, 11:11 PM

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...

27th March 2003, 10:21 PM	#8
Prune Account Disabled Join Date: Mar 2003 Location: Vancouver	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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15th March 2003, 06:46 PM	#3
jwb diyAudio Member Join Date: Mar 2002 Location: San Francisco, USA	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

17th March 2003, 05:28 AM	#4
maczrool diyAudio Member Join Date: Oct 2002 Location: Louisiana, USA	Nice work. What is the output level of the circuit? You did say it was a passive I/V design right? Stu

17th March 2003, 06:40 AM	#5
jwb diyAudio Member Join Date: Mar 2002 Location: San Francisco, USA	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.

17th March 2003, 07:43 AM	#6
kasra diyAudio Member Join Date: Nov 2001 Location: Sweden	Very nice! What is the size of the board? regards - kasra

17th March 2003, 02:34 PM	#7
maczrool diyAudio Member Join Date: Oct 2002 Location: Louisiana, USA	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

27th March 2003, 11:04 PM	#9
jwb diyAudio Member Join Date: Mar 2002 Location: San Francisco, USA	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 4.7µF 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 75Ω 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

27th March 2003, 11:11 PM	#10
Prune Account Disabled Join Date: Mar 2003 Location: Vancouver	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...