Differential out from two 1543 NOS DACs - diyAudio
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Old 29th November 2008, 03:27 PM   #1
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Default Differential out from two 1543 NOS DACs

What will happen if one takes two complete DACS and connect them with input transformers via SPDIF from the same digital source with one of the transformers phase-reversed? Will the analog signals be phase-reversed too?

If so, my idea was to use two complete simple NOS TDA1543 DACs and connect them with output transformers between the DAC 1s and DAC2s now differential outputs. As it is the same potential on the outputs(normally in the ballpark of 4V) transformers could now be used.

I donīt need any explanations or opinions about the arrangement, just if it will work or not.
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Old 29th November 2008, 04:39 PM   #2
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LL1573 as input transformer could be used with reversed phase on one output:

http://www.lundahl.se/pdfs/datash/1572_1573_1589.pdf
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Old 30th November 2008, 01:46 PM   #3
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Where my questions to stupid to answer ?
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Old 30th November 2008, 02:40 PM   #4
dddac is offline dddac  Germany
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This is what a DDDAC DIY did to get a balanced signal:
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Old 30th November 2008, 02:41 PM   #5
dddac is offline dddac  Germany
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and here is the circuit

very simple, take 2 dacs and send inverted data signal to it, which will generate an inverted analog signal ...
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Old 30th November 2008, 03:17 PM   #6
gmarsh is offline gmarsh  Canada
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Default Re: Differential out from two 1543 NOS DACs

Quote:
Originally posted by revintage
What will happen if one takes two complete DACS and connect them with input transformers via SPDIF from the same digital source with one of the transformers phase-reversed? Will the analog signals be phase-reversed too?
Fraid not. SPDIF is NRZ encoded, and will decode to the same data if you invert the transformer.

I'd use a single SPDIF receiver, but put an inverter on the I2S data line going to one of your DACs. This will invert the digital data going into that DAC, and will effectively invert the analog output.

(Please, oh please, don't let this turn into a discussion of 1LSB error.)
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Old 30th November 2008, 04:07 PM   #7
dddac is offline dddac  Germany
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Default Re: Re: Differential out from two 1543 NOS DACs

Quote:
Originally posted by gmarsh

but put an inverter on the I2S data line going to one of your DACs. This will invert the digital data going into that DAC, and will effectively invert the analog output.


as i posted before ?
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Old 30th November 2008, 04:36 PM   #8
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Thanks for the replies, it was like I suspected.

I have two identical DACs, and just hoped the solution would be even simpler. It will be no problem to use the input circuit on just one of them.

ddac, have seen variations on solutions like yours, but your version of phase inversion before the chips seems very simple and straigtforward with only one NAND-gate. As I am a novice on logic circuits what are the 5 others marked 2-3, 5-6, 9-8?

Couldnīt adjusting R7 be a way of minimising offset, or do L and R differ?
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Old 30th November 2008, 05:24 PM   #9
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Found the DDDACs buffers. Suppose they are not needed when using only one 1543 chip.
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Old 30th November 2008, 06:06 PM   #10
dddac is offline dddac  Germany
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Quote:
Originally posted by revintage
Found the DDDACs buffers. Suppose they are not needed when using only one 1543 chip.

correct !!
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