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Old 19th February 2004, 04:17 PM   #1
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Default PCM1798 mono mode with balanced output help

I need help on connection of PCM1798 in mono mode.
PCM1798

I would like to use one chip/channel, but there are four outputs in one chip (L-, L+, R-, R+)
How should I connect them to have only one - and + output?

Is it ok on this way?

L+ and R- -> +out
L- and R+ -> -out

It is like paralel the DAC stages.

Thanks for your help!
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Old 19th February 2004, 05:06 PM   #2
Lyra is offline Lyra  Norway
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See the datasheet.....

Lyra
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Old 19th February 2004, 06:04 PM   #3
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I saw it, but I want to use discrete I/V stage (D1), and not opamp stage.
D1 has only one - and + input.

Do I have to biuld 2 of them?
I am not sure.
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Old 19th February 2004, 06:36 PM   #4
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I was thinking in something like that.
Could it be work?
Because in mono mode L and R inverted:
L- and R+ same
L+ and R- same

Is it correct?
Is the output current is higher also?
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Old 19th February 2004, 06:43 PM   #5
Lyra is offline Lyra  Norway
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Think you will have to build two D1 stages including 16 pcs. of IRF610/IRF510, and use some kind of discrete-builded OP-amp to make the signals from each one "non-balanced", and then the sum on theese outputs will be balanced (again) ?!

Lyra

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"ICs and Transistors are working with smoke! If the smoke coming out, the part will not work anymore...."
hmmm......what will then happen to us that smoke sigarettes when we stop smoking......
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Old 19th February 2004, 06:51 PM   #6
Lyra is offline Lyra  Norway
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You where faster than me posting...
Yes....maybe this will work ?, but think you have to try and see if the PCM1798 will survive....

Lyra
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Old 19th February 2004, 07:25 PM   #7
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Quote:
Originally posted by mpopovics
I was thinking in something like that.
Could it be work?
Because in mono mode L and R inverted:
L- and R+ same
L+ and R- same

Is it correct?
Is the output current is higher also?
I think this is a GREAT question.

You have come to the same conclusion as I have. Be ware though that such current output devices (I have not evaluated your device) will have a standing current into the device which will go away in the subsequent diff-amp.

You also need to change the values of the resistors for the output amp unless you want double output swing. If you do so, remember that the rollof frequency is also affected by such change of resistors.

Please let me know your results.

Petter
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Old 2nd March 2004, 02:26 PM   #8
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Default The solution

I have asked TI directly, to get information.
They forwarded the question into Japan, to development dept.

Finally, after 2 weeks I got this answer:

"Dear Mr. Popovics,

please find the answer from our Japanese experts below:

"For two I/V amp circuit ( DF bypass, mono )
Connect IoutL- and IoutR+ -> I/V
Connect IoutL+ and IoutR- -> I/V

For four I/V amp circuit ( DF bypass, mono )
Shown in Figure-25, data sheet"

Please let me know if you have any further questions."

BR,
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Old 24th September 2005, 10:00 PM   #9
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Hello

I am also asking about dual mono PCM1798->out

mpopovics:
Did you tried it?


How did it sound?

Best regards

Kim
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