You are not logged in. Please login or register.
RME User Forum → ADI-2 & 2/4 Pro series, ADI-2 DAC series → upsampled PCM or also modulated DSD input to ADI-2 DAC FS
Is there a technically better way to provide externally upsampled PCM signal to the DAC ? what is the difference in terms of DAC's processing of externally upsampled PCM (756kHz) vs. PCM modulated to DSD(256) stream ? Is the PCM input internally converted to a DSD(like) stream or PCM and DSD handling is separate in the DAC chip ?
There's no technical benefit upsample your audio on your computer. In addition, RME software cannot process DSP on very high sample rate PCM or any DSD due to limitation of the processor. So you lose most of the benefits using the ADI-2 Pro/DAC.
DSD is converted to PCM by the DAC chip unless you use the DSD Direct mode, which unfortunately disable the volume attenuation.
Just send audio stream in its original rate. RME's DSP pipeline/ DAC chip's upsampling algorithm will do the upsample/downsample automatically for you. No need to worry about it.
There are, however benefits to convert your DSD to PCM on your computer on the fly and send PCM to the device, in order to utilize RME's DSP functionalities.
"DSD is converted to PCM by the DAC chip", do you mean full PCM or just some multi-bit for the DAC ? I couldnt find more information on the DAC chip. What I want to ask in other words, is there any difference of going from full PCM to some multi-bits (not sure if this is true) and going from 1-bit DSD to multi-bits ?
I missed the point with the DSD direct mode, thanks for that. So that would make a different path for DSD stream.
Regarding to oversampling, I was actually going to ask if the oversampling filter bypass is used somehow. So my point was if it is possible to do this oversampling externally and make the DAC work without oversampling filters.
This question is just a technical curiosity, I dont mean this would make sense sonically etc.
Also I missed the page in the manual for DSP limitations (just received the DAC yesterday), thanks for that. So for this discussion I can say externally upsampled up to 384kHz when I want to use something from the DSP.
> do you mean full PCM or just some multi-bit for the DAC ?
There's no (easy) way to do volume attenuation in DSD or multi-bit. So DSD has to be converted to PCM in the first place.
> is there any difference of going from full PCM to some multi-bits (not sure if this is true) and going from 1-bit DSD to multi-bits ?
answered above. unless you use dsd direct (no volume adjustment), all DSD has to be converted to PCM first. Then magic (oversampling/sigma-delta) happens after that. Refer to chips datasheet.
>So my point was if it is possible to do this oversampling externally and make the DAC work without oversampling filters.
you can choose nos filter but it's not available at higher sample rates. See manual "At sample rates higher than 192 kHz DA Filter selection is no longer available. The DAC then uses a fixed Slow filter." Also, disabling the dac filter (NOS) and doing it on your computer will not give you better result ---- DAC's own oversampling can do it at a much higher rate (256x for AKM4493, for instance) and achieve better result, while your computer will struggle upsampling at such high rate.
> Also I missed the page in the manual for DSP limitations (just received the DAC yesterday), thanks for that. So for this discussion I can say externally upsampled up to 384kHz when I want to use something from the DSP.
MC confirmed in another thread that the RME TotalMix FX technology will upsample your signal internally. So both DSP and DAC chip will do the upsampling work for you.
If you upsample it to 384khz and send it to the dac, the dac will then apply another filter to upsample it anyway, as mentioned above.
Better to run PCM and take utility of the DAC/PRO´s excellent DSP and volume control IMHO. I think you should do the experimenting and use your own ears though. Lots of software can upsample and do conversion, even on the fly with different algorithms and adjustable parameters.
I recomend u to get the info from the chip manufacturers AKM or ESS. Its all downloadable from their respective websites. They have schematics which show the inner workings. Do some plowing on this website. Most things have been written here at least twice 
Understandably RME is secretive about core technology, but u can add some things together to get a better understanding
There's no (easy) way to do volume attenuation in DSD or multi-bit. So DSD has to be converted to PCM in the first place.
Sorry I mistaken again (I focus too much on the DAC chip and forget the overall DAC unit, volume control, DSP etc.), what I should say is if there is a difference between upsampled PCM stream fed to (normal) PCM input, and upsampled PCM modulated to DSD fed to DSD direct input, but I at least need the volume control anyway as I dont have another preamp, so OK I got this point for the moment, no point in giving modulated DSD to non-direct DSD.
you can choose nos filter but it's not available at higher sample rates. See manual "At sample rates higher than 192 kHz DA Filter selection is no longer available. The DAC then uses a fixed Slow filter." Also, disabling the dac filter (NOS) and doing it on your computer will not give you better result ---- DAC's own oversampling can do it at a much higher rate (256x for AKM4493, for instance) and achieve better result, while your computer will struggle upsampling at such high rate.
Yes I read in a forum post before that after 192kHz it is always the Slow filter. Just to clarify, is the NOS filter effectively disable oversampling filter or is it just another filter that looks/functions/sounds like oversampling disabled ?
By the way, if/since DAC oversamples at a much higher rate internally, why is there such external upsampling options in the players ? Is it to be used with DACs that do not oversample ?
MC confirmed in another thread that the RME TotalMix FX technology will upsample your signal internally. So both DSP and DAC chip will do the upsampling work for you.
Actually the whole point of asking this was if PC could do the upsampling better, but I guess the answer is either no, or no from a technical pov.
I recomend u to get the info from the chip manufacturers AKM or ESS. Its all downloadable from their respective websites. They have schematics which show the inner workings. Do some plowing on this website. Most things have been written here at least twice big_smile Understandably RME is secretive about core technology, but u can add some things together to get a better understanding
I am quite familiar with checking datasheets etc. and I did not check AKM for a while but ESS seems to be quite not giving such information publicly. There is only the datasheet in the website which I dont think much detailed, and I saw only a few videos by ESS engineers. I did not still even get if ESS DAC (HyperStream) is multi-bit or not. Definitely I should go through the forum, I am sure these questions answered more or less before.
metebalci: I didnt mean you shouldnt ask but im sure youll find questions you didnt ask 
> Just to clarify, is the NOS filter effectively disable oversampling filter or is it just another filter that looks/functions/sounds like oversampling disabled ?
it doesn't really matter. The thing it matters is it works like a non-oversampling (old fashioned) DAC.
Technically NOS can be implemented by an FIR filter. RME achieved it this way --- this is exactly how they achieve NOS in ESS version of ADI-2 DAC.
> By the way, if/since DAC oversamples at a much higher rate internally, why is there such external upsampling options in the players ? Is it to be used with DACs that do not oversample ?
To those who really care about filters (most people don't care and are happy with the default one), some filters are not provided by DACs. The ESS chip used in latest ADI-2 DAC units, for instance, only provides very limited filters (maybe 2 or 3) by default. The rest are programmed by the RME and added it to the unit. This is a unique move RME made to ensure it's compatible with previous versions. Most device manufacturers don't add additional filters to their units. Because of lack of filters provided by DACs, this become the selling point for those players. You can do a ABX test on those filters provided by the unit (or software) and see if you can reliably tell the difference. I can't except for some very early roll off ones (NOS). Even for the NOS, the difference is so minor to me. On the other hand, the DSP technologies in this unit (EQ/BT/Crossfeed/Loudness/etc) makes HUGE difference to sound.
RME User Forum → ADI-2 & 2/4 Pro series, ADI-2 DAC series → upsampled PCM or also modulated DSD input to ADI-2 DAC FS
Powered by PunBB, supported by Informer Technologies, Inc.