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Old 25th October 2012, 01:50 PM   #1
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Default TDA7294 balanced input

Hi,

is it possible to add an balanced input to a classical
TDA7294 design?
Im using boards from xy Audio, ver 1.1.

I thougt that ive to add only a Resistor to the inv. Input.

Maybe some of you can help.

Thanx in advance,
Andreas
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Old 25th October 2012, 04:50 PM   #2
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Yes, it is possible. In the circuit attached, remove the ground side of R3 from ground, and put there the inverted input, but a balance in the circuit must be performed for properly job, put a 330nF (or other value in this line also as in the NI input, and the same 680R in series to the input), so maintain the input balance between line signals.

As this changes varies the amplification factor, perhaps oscillations can get, in such a case, re-calculate for more closed loop gain.

Good luck!
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Old 25th October 2012, 05:11 PM   #3
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What happens if nothing plugged into the input?
I think inverting input needs a resistor to ground. 22K?
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Old 25th October 2012, 05:13 PM   #4
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Quote:
Originally Posted by bobodioulasso View Post
What happens if nothing plugged into the input?
I think inverting input needs a resistor to ground. 22K?
Only in the + input, the - input 22K goes to the output, as in the circuit above.

If no input, in such case, the amp is balanced, and no output will be.
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Old 25th October 2012, 05:16 PM   #5
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You are right. Thx
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Old 25th October 2012, 05:28 PM   #6
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Which part of Europe are you from? My brother is living in Madrid from 2002.
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Old 25th October 2012, 05:33 PM   #7
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I am in France.
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Old 25th October 2012, 05:36 PM   #8
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OK. Good luck!.
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Old 25th October 2012, 09:05 PM   #9
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Thanx Oswaldo,

will try it this weekend.
And report.

Andreas
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