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Old 30th July 2006, 12:14 AM   #1
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Default USB powered NOS USB DAC with built-in headphone amp

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Schematic at: http://www.ecp.cc/images/HPDAC_0.1b_sch.GIF

Larger pic at: http://www.ecp.cc/images/HPDAC_IN_L.jpg
-d
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Old 31st July 2006, 04:29 PM   #2
kec is offline kec  United States
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dsavitsk, or anyone else,

Question: How is a OS DAC (PCM2706) changed into an NOS one? Please forgive me, I'm new to this DAC stuff. Just trying to learn.


-Ken
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Old 31st July 2006, 04:42 PM   #3
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Quote:
Originally posted by kec
dsavitsk, or anyone else,

Question: How is a OS DAC (PCM2706) changed into an NOS one? Please forgive me, I'm new to this DAC stuff. Just trying to learn.
In this case, the PCM2707 is only used to convert USB to I2S. This I2S signal (which is NOS) is sent to a TDA1543 chip to do the actual conversion from digital to analog. If the 2707 is used as a dac, then it probably oversamples or something, but I don't use it that way.

-d
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Old 31st July 2006, 04:50 PM   #4
kec is offline kec  United States
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That's what I kinda figured looking at the schematic, but just wanted to make sure.


Thanks,
Ken
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Old 2nd August 2006, 05:17 AM   #5
renfrow is offline renfrow  United States
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Pardon my newbness, but, is this something you would shove (appropriately :-) a wav file out a usb port to listen to music?

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Old 2nd August 2006, 03:03 PM   #6
kec is offline kec  United States
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Quote:
is this something you would shove (appropriately :-) a wav file out a usb port to listen to music
In a word, yes. But not only wav, any audio - although you would really only want uncompressed wav or lossless compression like flac, ape, etc. The reason is to get error free data without any correction to it.

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Old 8th August 2006, 07:04 PM   #7
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Some updates at http://www.ecp.cc/HPDAC.html
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Old 8th August 2006, 10:57 PM   #8
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Shouldn't PSEL be connected to GND? (LOW)
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Old 9th August 2006, 03:08 AM   #9
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Quote:
Originally posted by Akira386
Shouldn't PSEL be connected to GND? (LOW)
When used with an external PS then PSEL is low, but here it is USB Bus powered which means it needs to be high. PSEL high sets the HOST pin to be determinitive of max power draw from the bus, which here is set to 500mA.

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Old 9th August 2006, 04:11 AM   #10
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Making PSEL HIGH, the internal regulators are activated. Which makes the REG101 redundant.

Am I wrong?
If I am, then how PCM "knows" when to activate or deactivate the internal regs?
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