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Old 8th July 2004, 09:48 AM   #11
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Heyhey...

Nice, I've updated the PDF link following some of the advice here . So, I think i'll go with this circuit initially and if all is dandy try a 1dac per chan brd to see if theres any major dif...

A discrete i/v stage followed by a DOA (mebbe some iron too) would be lovely tho - it's just the expense/knowledge I lack there to implement correctly I think...

Thanks > again.
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Old 8th July 2004, 01:02 PM   #12
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Another pdf ;-) with some iron

http://www.kevinc927.addr.com/images...utputstage.pdf
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Old 8th July 2004, 01:32 PM   #13
borges is offline borges  Norway
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Congrats on your design!

I'm using the PCM1794 with my own oversampler (Xilinx demo board) to compare it to the PCM1704. I've got a 2nd order filter on a pair of 1704's and on the R outputs on a pair of 1794's. Then I've got a different filter on the L outputs on the same 1794's. According to TI/BB, the two types of DAC accept the same input data format.

Did anobody out there ever try using a passive IV converter on the 1794? I just need to run a few more simulations to determine my component values before I solder mine in. I hooked up four bias current sources based on 431's and big surface mount NPNs to remove much of the 6.2mA DC output current.

Besides, TI/BB could easily have been more instructive on the polarity of the different outputs when using the device in mono mode. I should have read the referred thread before designing my board, because now at least half my outputs are inverted.

Greetings,
BÝrge
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Old 8th July 2004, 01:37 PM   #14
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Hey Bas...

That looks nice...

So the i/v stage (just a few transistors?) in that pdf is powered by it's own tx and psu circuit - really needed? Im after 8 chans in a single box.

It looks nice n simple tho (am i missing summin) u just go from the dac (1794 here) outs to where it says ye? No opamps at all in the signal...


Cheers.
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Old 8th July 2004, 02:08 PM   #15
pooge is offline pooge  United States
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Quote:
Originally posted by borges
Congrats on your design!

Did anobody out there ever try using a passive IV converter on the 1794?
Greetings,
BÝrge

K&K is coming out with a passive output with resistor I/V and transformers:

http://www.kevinc927.addr.com/digitalaudio.html
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Old 8th July 2004, 02:10 PM   #16
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Project development history

http://www.audioasylum.com/forums/Ka...ages/2397.html

Quote:
is powered by it's own tx and psu circuit - really needed?
I suppose that tx could power 8 channels..the rest of the psu would need to be multiplied.
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