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Old 6th September 2010, 01:51 AM   #51
sendler is offline sendler  United States
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Default Mono mode

I'm interested in trying my Gigaworks big dac boards with PCM1798 with a passive transformer I/V and want to use mono mode to increase the available output level. Where did you find the info on the output connections showing L+ tied parallel to R-. The PCM1794a data sheet doesn't show any info on a direct parallel connection for mono mode.
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Old 8th September 2010, 07:58 AM   #52
novec is offline novec  Norway
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The direct parallel is taken from an Analog Devices datasheet (can't remember which one), and has been confirmed by TI on another user's request. And no, I can't remember where I read that, either :-)

The reason TI hasn't mentioned it in their datasheet is because they consider the summed output current too high for their recommended output circuits, but it might be just what the doctor ordered for your application.
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Old 8th September 2010, 10:34 AM   #53
sendler is offline sendler  United States
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Default Dac Final

I did find another web page evaluating dac chips in mono mode.
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DAC Final
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Old 9th September 2010, 01:45 PM   #54
novec is offline novec  Norway
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Nice to get another confirmation of the connections. I'm not too worried about their test results, though. First of all, the PCM1794A is not designed for passive I/V. Secondly, it (and probably the others, to a varying degree) is sensitive to PCB layout, like bypass caps, ground scheme and so on. DIP adapter and proto boards aren't exactly optimal for sensitive electronics... Even so, tests like these are always appreciated!

I haven't had the time to work on my DACs this summer, but it looks like my schedule is opening up a bit. I'll keep you posted as I go along!
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Old 4th June 2012, 07:58 PM   #55
xslavic is offline xslavic  Moldova
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Default Hi

hello
im trying to build a Pcm1794a in dual mono,can someone tell me if i should use a resistor before opamp input ?the currents were summed + 100ohm to ground
ill use something like opa2227
here is the schematics PCM1794 dual mono i/v converter - conversion - stage :
ill use 2sc2362 instead of BC547 /SA970 / 2 SC2240
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