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Building the ultimate NOS DAC using TDA1541A
Building the ultimate NOS DAC using TDA1541A
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Old Today, 04:31 PM   #6721
batteryman is offline batteryman  United Kingdom
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Join Date: Jun 2011
Location: SCOTLAND
Quote:
Originally Posted by wlowes View Post
Like many, I have used Ian's PCB with the 1541a for several years. It works and to my ear sounds great at 44k to 192k without issue. But if I understand correctly that does not mean it is as good as it could be. If I am not mistaken, getting 15 bit depth vs 16 does not mean it does not work. It means we are running with a lower signal to noise ratio than the rated performance of the 1541a.
The way I see it is:

Losing the LSB is not that important as it is 1/65536th of the original resolution which won't affect the SNR or be audible. (Its not that the bits have all been shifted right resulting in 15bit data which would half the resolution to 32768)

All 16bits are processed by the board, but just that the 16th is (apparently) not clocked in - i.e. its missed so presumably its latch content will not change but all other 15 will be correct. The dac accuracy is only 0.5 - 1 LSB anyway so the LSB could be wrong by chance.

I have attached what I think is functionally equivalent of the 1541's input, register & latch (only 8 bits shown).
The data appears at the output of the register and is available to the latch when LE goes high according to the data sheet.

But according to Ian, the latch does not actually freeze the data until LE goes low, hence he says the LSB is not missed.

However, only in the multiplexed modes does the falling edge of LE latch the data so is Ian wrong, or is the datasheet not explicit or does it not actually matter?
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Last edited by batteryman; Today at 04:59 PM.
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Old Today, 06:56 PM   #6722
wlowes is offline wlowes  Canada
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Join Date: Mar 2007
Location: Toronto
S/N Limits of
a CD is 96dB.
the TDA1541A is 98 - 110dB.
the Human auditory system is approximately 21 bits or 123dB.

I believe 15 bit audio is around 90dB. I suspect most of us will hear it. It may fall into the territory of do you hear difference in cables, but at least this one has a measurement.
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Old Today, 08:23 PM   #6723
Markw4 is offline Markw4  United States
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Undithered bit-depth reduction from 16-bits to 15 should be audible to at least some people.
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