SAA7220 spdif question

[UV101]

Hi can anyone tell me if the spdif out on the 7220 is generated before or after the filter??? I don't ever remember seeing the answer posted on the forum before!

Happy Christmas

[QSerraTico_Tico]

Originally Posted by UV101

Hi can anyone tell me if the spdif out on the 7220 is generated before or after the filter??? I don't ever remember seeing the answer posted on the forum before!

Happy Christmas

Before of course. SPDIF out is not digitally filtered.

[UV101]

Thanks, I thought it would be ;-)

[SoNic_real_one]

If it was so, it would push the data rate to 4x of the original digital signal. Back then it was not fesable.
It's raw digital, all the filtering and OS is left for the receiver/DAC stage.

[UV101]

Ok so humour me........

What would happen if you fed the i2s out that was destined for the tda, into another 7220. This would then generate spdif based on the filtered data? Also I wonder how this would effect the sound at the tda? Not sure ive ever read about anyone trying multiple filters in line!

[amc184]

I wouldn't expect it to work. The SAA7220 is designed to receive non-oversampled data, you won't be able to just stack them. However, a modern S/P DIF transmitter, such as the DIT4192, shouldn't have any problem converting the filtered I2S output of a SAA7220 into a S/P DIF stream, if that's what you're trying to do.

[SoNic_real_one]

In my experience, SAA7220 does a fairly lousy job as OS filter. The number of FIR coeficients is limited (4x30 coeficients), based on what was technically fesable back then.

[UV101]

Was more from a curiosity point of view than trying to achieve anything. Surely the second filter would have no comprehension that the i2s has already passed a filter??

[abraxalito]

Originally Posted by SoNic_real_one

In my experience, SAA7220 does a fairly lousy job as OS filter.

Lousy in regards to sound quality or lousy in terms of stop-band rejection? What have you compared it to?

The number of FIR coeficients is limited (4x30 coeficients), based on what was technically fesable back then.

Not to mention that the coefficients themselves are 12bit values. More would help in getting a steeper transition band (and hence more ringing) - I'm not myself yet convinced that longer means better.

[SoNic_real_one]

I have a Phillips with the SAA7220 and TDA1541. Replaced the OpAmps (LM833). Sounds artificial, that dry "CD sound" that everybody talks about and they keep repeating since the 90's. Some blaim the jitter, some the filters, some the fact that was a rush 16 bit job from the 14 bit that they had in mind. Probably the limited RAM that SAA7210 has doesn't help either (Sony parts had double that ammount).
Based on the stories here, I did try the NOS on it - even worse, back to OS. I sometimes pull it out and try to listen to it. To me, it is boredom.

Sure I can see the apealing side to it - BIG chips, BIG terminals, all trough-hole parts, any beginner can play with it. And whatever you do to it it still doesn't leave the feeling of "I'm done, perfect sound, now I can LISTEN the music". You keep on tinkering...

PS: I did hear once a Denon DCM-560. I did like it (the sound) and wanted to know what was different. CXD2500 with 32kB RAM. SM5845 as filter. PCM61P as DAC. I almost bought it - then I realized that the price was too high for what it was. A nicer CD player than my Phillips.