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Old 5th June 2007, 06:33 PM   #1
SunRa is offline SunRa  Romania
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Default I2s Pcm2704/07


I am trying to figure out how to configure a USB dac around the PCM2704/07.

Most of the ideas are from here: Final DAC .

The thing is that I don't want to use the CS8416 circuit yet (I don't need spdif or toslink) and even the usb is just a temporarely solution, mostly for experimentation purposes. Even if this circuit uses asyncronous reclocking (wich I'll use too) I still don't like the spdif conection (via the lundahl 1572) between the pcm2704 and the cs8416. This is another reason for not using it as it is, at least for now.

Now the question. Looking in the PCM2704/07 datasheet I initialy thought that both ofer I2S output to feed the ASRC (I thought that they are the same chip in different packages). Now I believe I am wrong, the pcm2704 has just spdif out and the PCM2707 has the I2S. Well, am I corect?

If yes, could I use the PCM2707 in this configuration here to feed the ASRC?

Thank you
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Old 5th June 2007, 09:31 PM   #2
rja is offline rja  United Kingdom
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PCM2707 and PCM2706 both output i2s or spdif. Pin 9 allows selection of either format.

That schematic should work - be sure to use the one in the third post though. The datasheet includes a reference schematic on page 30 - the basis for 00940's design, I believe.

Don't forget the 3.3v and 5v supply differences... and try to keep the i2s bus as short as possible.

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Old 6th June 2007, 07:24 AM   #3
SunRa is offline SunRa  Romania
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Hello Rich,

Thanks for the reply. I was aware that PCM2707 has both spdif and i2S... only that I was locked on using PCM2704 and was wondering where are those I2S outputs . Now I know...
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Old 8th June 2007, 08:45 AM   #4
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Please look cearfuly, 2706 and 2707 can't do SPDIF and i2s output at the same time, because spdif data and i2s data shares the same pin.
There is no miracles, just short circut and circut brake.
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Old 8th June 2007, 08:54 AM   #5
SunRa is offline SunRa  Romania
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Thanks s_volkovoy,

Yes, I've noticed that too... I think the confusion was because I was "locked" on one of the versions...
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Old 26th July 2007, 05:10 PM   #6
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I have a problem with PCM2706. I use it with CS4398 with I2S connection, it works, but there is quite a lot of distortion only above -8dB, and this is well seen on the oscilloscope, and frequency independent. What would be wrong? The CS4398 hase 5 volt supply well regulated and decoupled, I use only smd parts, the analog section has its own supply+/-15V
Thanks for thinking
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