11-Jul-2015, 04:58
11-Jul-2015, 12:01
No it isn't straightforward, it's not possible. The DAC inside the Devialet (TI PCM1792A) doesn't support anything higher than DSD64 (sample rate of 2.8224 MHz). So if Devialet would implement support for DSD128 it would mean they're down sampling.
http://www.ti.com/lit/ds/symlink/pcm1792a.pdf
http://www.ti.com/lit/ds/symlink/pcm1792a.pdf
11-Jul-2015, 18:41
(11-Jul-2015, 12:01)Antoine Wrote: [ -> ]No it isn't straightforward, it's not possible. The DAC inside the Devialet (TI PCM1792A) doesn't support anything higher than DSD64 (sample rate of 2.8224 MHz). So if Devialet would implement support for DSD128 it would mean they're down sampling.
http://www.ti.com/lit/ds/symlink/pcm1792a.pdf
DSD64 would be converted to PCM for all Devialets DSPing long before it needs to be converted to analog. So In theory DSD128 should be possible as long as it has the power to do the PCM conversion on it.
11-Jul-2015, 18:56
MAT® converts DSD into 40bit/384 kHz, thanks to an optimised algorithm limiting the amount of computational operations on the audio stream. Using only 15 bit perfect additions (no multiplication, no storage) MAT algorithm performs a 128 taps, linear phase FIR (Finite Impulse Response) digital filter ensuring the conversion of the DSD format into the internal native PCM format.
So, now the question is how can the PCM 1792, which is limited to 24bit/192 khz handle 40bit/384 kHz?
From Devialet:
In all our Expert units, we use one 1792 chip per channel allowing a doubled bandwidth compared to stereo designs employing only one chip.The audio resolution you mention is our computational resolution in our various processors and has to be seen as a maximum value.
BTW, the Aesthetix Pandora Signature also uses the PCM 1792A, and it does 1X and 2X DSD. From their website:
True Native DSD
Romulus and Pandora Signature offer true native DSD 1x and 2x functionality over USB and 1x DSD over SPDIF (AES/EBU, RCA Coax and TosLink). The entire DSP processing section is replaced. The new section includes an advanced Xilinx gate-array which allows the DSP to be completely bypassed for pure DSD 1x and 2x operation. No alteration of DSD data occurs. Many DACs in the market that claim to play DSD actually convert the data to PCM and thereby completely lose the purpose of DSD operation.
So, now the question is how can the PCM 1792, which is limited to 24bit/192 khz handle 40bit/384 kHz?
From Devialet:
In all our Expert units, we use one 1792 chip per channel allowing a doubled bandwidth compared to stereo designs employing only one chip.The audio resolution you mention is our computational resolution in our various processors and has to be seen as a maximum value.
BTW, the Aesthetix Pandora Signature also uses the PCM 1792A, and it does 1X and 2X DSD. From their website:
True Native DSD
Romulus and Pandora Signature offer true native DSD 1x and 2x functionality over USB and 1x DSD over SPDIF (AES/EBU, RCA Coax and TosLink). The entire DSP processing section is replaced. The new section includes an advanced Xilinx gate-array which allows the DSP to be completely bypassed for pure DSD 1x and 2x operation. No alteration of DSD data occurs. Many DACs in the market that claim to play DSD actually convert the data to PCM and thereby completely lose the purpose of DSD operation.
11-Jul-2015, 19:42
(11-Jul-2015, 18:41)Dr Tone Wrote: [ -> ](11-Jul-2015, 12:01)Antoine Wrote: [ -> ]No it isn't straightforward, it's not possible. The DAC inside the Devialet (TI PCM1792A) doesn't support anything higher than DSD64 (sample rate of 2.8224 MHz). So if Devialet would implement support for DSD128 it would mean they're down sampling.
http://www.ti.com/lit/ds/symlink/pcm1792a.pdf
DSD64 would be converted to PCM for all Devialets DSPing long before it needs to be converted to analog. So In theory DSD128 should be possible as long as it has the power to do the PCM conversion on it.
Yes you're right, forgot about the conversion for DSP purposes. Also converting it back to DSD after the DSP stage seems unlikely so I guess it should indeed be possible as long as there's enough processing power in the FPGA.
13-Jul-2015, 05:56
(11-Jul-2015, 19:42)Antoine Wrote: [ -> ](11-Jul-2015, 18:41)Dr Tone Wrote: [ -> ](11-Jul-2015, 12:01)Antoine Wrote: [ -> ]No it isn't straightforward, it's not possible. The DAC inside the Devialet (TI PCM1792A) doesn't support anything higher than DSD64 (sample rate of 2.8224 MHz). So if Devialet would implement support for DSD128 it would mean they're down sampling.
http://www.ti.com/lit/ds/symlink/pcm1792a.pdf
DSD64 would be converted to PCM for all Devialets DSPing long before it needs to be converted to analog. So In theory DSD128 should be possible as long as it has the power to do the PCM conversion on it.
Yes you're right, forgot about the conversion for DSP purposes. Also converting it back to DSD after the DSP stage seems unlikely so I guess it should indeed be possible as long as there's enough processing power in the FPGA.
BTW, isn't DSD64 the same or approximately the same as as 352kHz/24bit?
If so, why doesn't Devialet release firmware with PCM at 352kHz/24bit?