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Old 6th November 2001, 10:18 AM   #1
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Hi everyone!

I plan to build a dac with upsampling, use cs8420 + cs43122 or cs8414 + ad1896 + ad1853, I'm looking for some suggestion.

On cs43122 Eval board, there's no LPF follow the dac, but cs4397 Eval board has a LPF, why? for cs43122 has second generation DEM while cs4397 has not? should I add a LPF after cs43122?

Another question is how to design a differential input LPF? how to transfer a single input LPF design to differential ? Can I just add a balance impedance the same as input+ to OP's input- and wire it to the output- of dac?

I can't browse http://www.diyaudio.de, can anyone mail DAC 4's data to me? Thanks.

shizr@263.net
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Old 7th November 2001, 06:04 AM   #2
hifiZen is offline hifiZen  Canada
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crystal semiconductor has an appnote on their website somewhere about how to build a differential input LPF. As far as the C43122 goes, i would still include a low-pass filter. A cutoff frequency of maybe 60kHz should do nicely, without interfering much with the audio band.
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Old 7th November 2001, 06:09 PM   #3
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C Simpson,
I found the appnote--an48.pdf, I will try Bessel type, and compare it to Butterworth type.

Thank Sonny for DAC 4s information.
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Old 8th November 2001, 02:31 PM   #4
hifi is offline hifi  Sweden
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hmm....how far into this project are you im planing to build an dac with cs8420 and cs43122 aswell..

/micke
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Old 9th November 2001, 12:46 AM   #5
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micke,
Now I am searching the parts, I will not start drawing pcb until I know the footprint of the part which I can get. I also plan to order special frequency TCXO from the local factory, to get a 1 ppm clock. for me it cost less than Lcclock XO2.
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Old 9th November 2001, 03:28 AM   #6
Dave is offline Dave  New Zealand
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I have used the CS8420 with a DF1704 and PCM1704s.

If you are interested take a look, http://www.geocities.com/d_broadhurst/index.html

If you want the schematics send me an e-mail.

gene - Where can you get a TXCO?
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Old 9th November 2001, 03:31 AM   #7
Dave is offline Dave  New Zealand
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I forgot to mention, Crystal have told me only to use Revision D of the CS8420 or better. Apparently earlier ones had problems.
Also the CS8420 must have an external reset pulse when you turn it on.
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Old 9th November 2001, 05:44 AM   #8
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Dave,
I can't browse any web base on geocities, what a pity.
please send it to shizr@263.net, thank you .

TCXO are normally between 10M to 20M, you can buy 12.8M/14.4M/16.5M TCXO anywhere for just several $, but special TCXO such as 24.576M /33.8688M for dac is not available from retail market. Maybe too expensive for consumer products. My company use 70M and 81.264M (1 ppm) from a local factory, they can make any value as you specified, so I decide to order some 49.152M from them. It can be divided to 24.576/12.288M.

Use an ad9850 to build a DDS clock source maybe a good solution, you can get any frequency with the same circuit, but I don't know how to do it.

[Edited by gene on 11-09-2001 at 12:46 AM]
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Old 9th November 2001, 10:12 AM   #9
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I am going to order some TCXO for DAC and CDP use. If someone want to order can leave the message here or e-mail to me for the detail!

The TCXO are from Japan and Raltron(USA). The price is about USD$45 (not include shipping cost)

I've got some of the 33.8688MHz on hand(Japan)

Hope can help you all!!

Thanks!
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Old 9th November 2001, 11:53 AM   #10
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how about use AK4114 as DIR? It's a 32 - 192kHz DIR from AKM.
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