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rsrphotos 1st April 2004 10:06 PM

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


renes3 2nd April 2004 05:02 PM

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!!!!!!!!!

aparatusonitus 2nd April 2004 06:46 PM

Send me a e-mail, I have SAA7378 datasheet thanks to Guido Tent.

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