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View Full Version : 88.2/96khz upsample w/SB2 internal DAC possible?



usualsuspects
2005-09-10, 11:25
The datasheet for the PCM1748 (DAC used in SB2) is 24bit/96khz. I see that the 16 to 24bits resampling is being done, but could the SB2 also be made to do 44.1 to 88.2khz and 48 to 96khz upsampling? Or is it already doing that?

seanadams
2005-09-10, 12:22
The datasheet for the PCM1748 (DAC used in SB2) is 24bit/96khz. I see that the 16 to 24bits resampling is being done, but could the SB2 also be made to do 44.1 to 88.2khz and 48 to 96khz upsampling? Or is it already doing that?

We feed the DAC at 44.1/48. I don't think there is any advantage to upsampling before the DAC, as the DAC does this anyway (8x oversampling for the digital filter). Keep in mind upsampling (aka oversampling) is the same as "digital zoom" in a camera - it doesn't add any new information. The DAC does it internally in order to apply a sharper/better/cheaper filter than can be achieved with analog passives.

Would be more interested in 88.2/96KHz support for those native file formats. I haven't yet looked at what all it would take to go to 96KHz - obviously clock rates, data rates, and CPU cycles double all over the place. It's not outside the realm of feasibility though.

Triode
2005-09-10, 15:45
There is a school of thought that upsampling in software means you can build more accurate digital filters etc...

See some discussion at: http://db.audioasylum.com/cgi/m.mpl?forum=pcaudio&n=4690&highlight=secret+rabbit&r=&session=

Having played with this foobar upsampler, it can eat most of the CPU cycles on my PC, but does make some 'difference' via the RME sound card in my 2G Athlon PC - [NB I'm not claiming it is better!] Hence the more complex functions aren't realistic for a SB2 type device in software, but could be an option for server side upsampling if the rest of the chain could do 24/96.

pasodoble
2005-09-17, 11:59
I've been playing about with upsampling for a while now, but I don't think it can beat a good non upsampling DAC. Yes, they do 'stuff' to the sound but I don't think it's worth doing. It is just like a digital zoom as other people as said... you can print it out bigger, but it's not higher quality.


I'm having a dabble with the Reimyo DAP-777 at the moment, and am becoming intrigued in a moth-to-light-sorta-way by the Progression / Dumpty combo.


I'm far more interested in 24/96 playback and of the potential of things like the service Onkyo started recently. http://music.e-onkyo.com/
24/96 downloads direct from the masters, if I'm led to believe correctly. Now this would be interesting, if only to highlight the crappiness of what passes for masters these days :p

joshk
2005-09-19, 11:48
FWIW, I'm very interested in 24/96 playback for native file sources and I do have some. I too am of the phil that there is little point to upsampling a 16/44 file.

abdomen
2005-09-19, 13:19
Would be more interested in 88.2/96KHz support for those native file formats. I haven't yet looked at what all it would take to go to 96KHz - obviously clock rates, data rates, and CPU cycles double all over the place. It's not outside the realm of feasibility though.
I have music files that are natively 96KHz, and I'll add my voice to those who would be thrilled to see this capability eventually added to the SB2.