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Building the ultimate NOS DAC using TDA1541A
Building the ultimate NOS DAC using TDA1541A
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Old 25th June 2018, 05:04 PM   #6211
SSerg is offline SSerg  Russian Federation
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Hi Shinja,
Quote:
Originally Posted by Shinja View Post
SSerg, are you talking about sign magnitude binary code?
I'm saying that TDA1541 only accepts data in two formats: OB and TWC. In no other form will you be able to transfer data correctly inside the TDA1541 chip. In both formats, the MSB is interpreted by the chip as a number sign, and 15 bits remain on the mantissa.
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Old 25th June 2018, 05:14 PM   #6212
Alexandre is offline Alexandre
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Quote:
Originally Posted by SSerg View Post
No, it depends primarily on the capabilities of the DAC chip.
Serg, the input to each channel is still 16 bits of course.

It is the input to the segment logic that can be 17 bits. Like I said it is possible to create a JRiver plugin that will take 24 bits input and add TPDF dither at the desired level. Make the TPDF dither with 2 bits peak to peak amplitude, adjust the level so it lands at bits 16 and 17, and add it. This can be tweaked too. One can experiment with noise shaped dither.

Interface between PC and segment logic still works at 24 bits. It is the job of the segment logic to work only with the 17 most significant bits.

Thanks,
Alex
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Old 25th June 2018, 05:20 PM   #6213
Alexandre is offline Alexandre
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Serg,

I canīt say I have scrutinized the logic like John has. But it seems to me perfecly feasible.

Am I missing something?
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Old 26th June 2018, 08:35 AM   #6214
SSerg is offline SSerg  Russian Federation
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Hi Alexandre,
Quote:
Originally Posted by Alexandre View Post
Am I missing something?
The idea is clear. You create two 16-bit segments from a 24-bit signal, and the 17th bit is controlled by an external interface. So?

The problem is that TDA1541 of each segment will perceive the high bit of this 16-bit segment as a sign. Do you understand? This is how TDA1541 (and TDA1540) is constructed, and it can not be altered. The player here does not help. The problem lies in the hardware.

Sincerely
Serg
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Old 26th June 2018, 12:55 PM   #6215
Shinja is offline Shinja  Japan
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MSB is a sign, so what is the problem here? In TDA1541 it just switches 2mA current source (or should I say sink?) to the output or ground. Boolean is fliped whether input format is OB or TWC.
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Old 26th June 2018, 01:48 PM   #6216
SSerg is offline SSerg  Russian Federation
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Quote:
Originally Posted by Shinja View Post
MSB is a sign, so what is the problem here?
The problem is that with TDA1541, you can not form a 16-bit segment (or 16-bit integer number), only 15-bit. Because for the mantissa of number stay only 15 bits.

The total DAC, which has two 15-bit segments, is equivalent to a 16-bit DAC, but not 17-bit DAC.
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Old 28th June 2018, 05:14 PM   #6217
JOSI1 is online now JOSI1  Germany
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Simultaneous Protocol Converter

Hello John,
is it possible that the converter described in post #7078/7079 (timing diagram/schematic) creates a delay of 64 BCK cycles between right and left
channel measured at the output of TDA1541A. With TDA1541A connected to
I2S there is no delay.
Thanks
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Old 29th June 2018, 01:47 AM   #6218
rfbrw is offline rfbrw
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Default It's a dac, Jim, but not as we know it.

So you folks think you can turn a COB/BTC dac into a straight binary dac. Interesting.
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Old 29th June 2018, 04:37 AM   #6219
weissi is offline weissi  Austria
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Just as an information to all the others, COB explained:
http://www.ti.com/lit/an/sbaa042a/sbaa042a.pdf
__________________
regards / servus
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Old 29th June 2018, 08:27 AM   #6220
SSerg is offline SSerg  Russian Federation
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Quote:
Originally Posted by weissi View Post
Just as an information ...[/url]
Thank you, useful document.
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