Bypass digital filter in PCM1794?

ezkcdude · 10th April 2006, 08:09 PM

The spec sheet for PCM1794 says the internal digital filter can be bypassed. Has anyone used it in this capacity, and wouldn't this be equivalent to a non-OS DAC?

b-square · 10th April 2006, 08:21 PM

Quote:

Originally posted by ezkcdude
The spec sheet for PCM1794 says the internal digital filter can be bypassed. Has anyone used it in this capacity, and wouldn't this be equivalent to a non-OS DAC?

the internal digital filter bypass is used along with an external filter. the data rate is still expected to be based on oversampling of the original input data. there is no mode documented in the data sheet that allows data straight out of a digital receiver to get sent directly to the dac without oversampling.

(reading back over the datasheet, it might be ok to drive WDCK at a "non-OS" rate...other dacs that allow internal DF bypass typically expect the behavior i mentioned above).

bb

ezkcdude · 10th April 2006, 08:41 PM

I also found that AD1955 could be used in a similar fashion.

ezkcdude · 10th April 2006, 09:13 PM

What I am thinking is something like CS8414->AD1896->PCM1794 (or AD1955). Therefore, it involves upsampling, which is admittedly not quite the same as a non-OS DAC. However, it does avoid the issue of the brickwall filter at the DAC stage.

chris719 · 11th April 2006, 12:16 AM

You do not avoid anything but one more FIR filter doing this, I'm not sure why you think the ASRC's polyphase FIR filter is less harmful than the integrated DF in the PCM1794, but maybe you could try it both ways and see what you think.

ezkcdude · 11th April 2006, 03:35 AM

Man, I was thinking about using the PCM1704K, but that chip is expensive! Is it worth the extra cost?

10th April 2006, 08:09 PM	#1
ezkcdude diyAudio Member Join Date: Dec 2005 Location: Atlanta	Bypass digital filter in PCM1794? The spec sheet for PCM1794 says the internal digital filter can be bypassed. Has anyone used it in this capacity, and wouldn't this be equivalent to a non-OS DAC?

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10th April 2006, 08:41 PM	#3
ezkcdude diyAudio Member Join Date: Dec 2005 Location: Atlanta	I also found that AD1955 could be used in a similar fashion.

10th April 2006, 09:13 PM	#4
ezkcdude diyAudio Member Join Date: Dec 2005 Location: Atlanta	What I am thinking is something like CS8414->AD1896->PCM1794 (or AD1955). Therefore, it involves upsampling, which is admittedly not quite the same as a non-OS DAC. However, it does avoid the issue of the brickwall filter at the DAC stage.

11th April 2006, 12:16 AM	#5
chris719 diyAudio Member Join Date: Jun 2004 Location: Connecticut	You do not avoid anything but one more FIR filter doing this, I'm not sure why you think the ASRC's polyphase FIR filter is less harmful than the integrated DF in the PCM1794, but maybe you could try it both ways and see what you think.

11th April 2006, 03:35 AM	#6
ezkcdude diyAudio Member Join Date: Dec 2005 Location: Atlanta	Man, I was thinking about using the PCM1704K, but that chip is expensive! Is it worth the extra cost?