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Old 1st April 2004, 10:06 PM   #1
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Default Upsampler for Njoe Tjoeb - theory of operation

This falls in the 'i'd rather not be working today' category.... feel free to ignore!

I have been mentally deconstructing my Njoe Tjoeb 4000 player and have some basic questions about upsampling/oversampling stuff.

This player uses a SAA7378 - TDA1545 combo. I believe that the 7378 performs 4x oversampling, hence the 1545 works on 16bit/176.4kHz data.

The upsampler board for this player replaces the 1545 DAC (and the voltage gain op amps) hence takes as input the 16bit/176.4kHz data stream. The info on the upsampler claims it uses a sample rate converter (I believe a Crystal CSxxxx) which sends 24bit/192kHz data to a single Wolfson DAC (their top of the line one used in the Arcam CD73) and then to some voltage gain op-amps.

So, my questions are :

- Who knows where I can get a data sheet for the SAA7378 chip

- What are the issues involved in performing a 16/176.4 -> 24/192 data conversion. In general one would not expect this to work so well. This is a very generic problem in digital audio I realize, perhaps someone can point me to some good papers/reviews explaining the issues and common solutions.

- I find it hard to believe that the supposed better performance of this player with the 'upsampler' is not simply due to the use of a much more modern lower noise DAC. Hence 'upsampling' being used as nothing but marketing hype?!?!

Thanks for any info and help in wasting more of my employers time

R
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Old 2nd April 2004, 05:02 PM   #2
renes3 is offline renes3  Zimbabwe
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Join Date: Mar 2004
Location: Uranus
Interesting point you got there,

Upsampling as a marketing instrument!

The upsampling board has better components, with good specs. If you compare these to the components that are originally in the Tjoeb (1545 +opamps), you'll really wonder if the better sound is due to upsampling.

But I traded mine for a cd80, so I don't bother anymore!!!!!!!!!
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Old 2nd April 2004, 06:46 PM   #3
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Send me a e-mail, I have SAA7378 datasheet thanks to Guido Tent.
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