DSD vs PCM

date_range 25 November 2024
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DSD vs PCM

Most music listeners have a vague idea of what the technical specifications of your streaming service or CDs mean, and many have also heard the acronym “PCM” - but perhaps they also know DSD, and wonder if this format could be relevant for you, maybe even better?


Let's have a look.

The overview: what's in it?

PCM (Pulse Code Modulation):

  • Audio CD format and used by lossless streaming services                
  • Resolution: 16 bit/ 44.1 kHz  
  •          
           

DSD (Direct Stream Digital):                          

  • Format of the Super Audio CD (SACD)                
  • Resolution: 1 bit/ 2822.4 kHz (2.8 MHz)  
  •          
 

The principle

Audio CDs are sampled “often enough”, i.e. 44,100 times per second - this means that a DA converter can recognize frequencies up to 22,050Hz without any doubt, and are stored at this interval with a depth of 16 bits, which contain the exact volume information.

The SA-CD samples 2.8 million times per second. The SA-CD samples so often because the information does not contain exact information about the volume, but only relative information: a value of 0 means we are going down a little, a value of 1 means we are going up a little.

To reproduce a rapid change in volume, such as a single drum hit on the drums, the signal must be sampled very often in order to capture it correctly.

The given resolution supports a frequency range of up to 50kHz, compared to the 22.05kHz of Audio CD.

Audio CD, although called lossless, is absolutely a consumer format: Sony, for example, exclusively uses DSD as the archive format in their productions.

Why is this relevant?

The frequency range that these two formats can reach is not necessarily relevant for the human ear, but for the electronics behind them. There are converters that can only handle PCM - there are converters that can also handle DSD, and there are converters exclusively for DSD.

Practical example: RME Adi-2 Pro      

This converter can process PCM and DSD and offers various filter options:

           
  •          
     
As you can see here, there are filters that have an audible effect at audio CD resolutions as low as 12 kHz!
As a reminder: This is not an EQ that you activate for reasons of taste, this is a filter that is intended to filter out the background noise of your own activity and which you should ideally not hear for this reason. The same filter works with a 96kHz signal only from approx. 25kHz.
The filter has to work with the signal it receives - and with a signal up to 22,050Hz it doesn't have much leeway. One converter that avoids this very nicely is the Ferrum Wandla - it simply upsamples internally up to 384kHz, so that any filter the listener chooses is guaranteed to work outside the audible range.
For DSD the RME has 2 filters on board, one from 50kHz and one from 150kHz, which can be used with higher resolution DSD material - both of course completely outside the audible range.
If you are now feeling a little wistful and thinking to yourself: What a shame that the wrong format seems to have won here, because DSD sounds much better on paper than the audio CD: Do the comparison yourself!
If your converter can also handle DSD, you can try out the demo version of HQ Player as playback software - provided you have a computer with a reasonably up-to-date CPU, the developer recommends “2 CPU cores per audio channel”.
This can convert PCM to DSD in real time and perform upsampling, and some users swear that DSD sounds significantly better than PCM with some converters.

     

Personal impression

I myself have compared CD and SACD (and vinyl) of the same albums in extended listening sessions, and find that the SACD sounded much more like vinyl than CD.

This is meant to be positive, because you could feel the bass of the record - the bass of the CD was only perceived as a deep sine tone, and everything else was just as accurate, but flat.

The filter design for DSD is much simpler than that for PCM, which explains the impression that it is probably the more “analog” format.

         

Conclusion      

This is just a brief introduction to the topic, in case you were ever curious about the format - to summarize:

           

     

  • Unfortunately, DSD is rare, not all music is published in this format and not every DAC can handle it. If you still want to listen in DSD format, a PC setup is a must.                
  • PCM is a consumer format whose technical disadvantages we have to accept in principle - apart from upsampling like Ferrum does, there is no solution to keep the filters out of the audible range - or you can do it yourself, e.g. with HQPlayer.            
       

 

Tags: audio formats DSD PCM |
Andreas Wagner

Founder of Level Audio, trained sound engineer and a hi-fi enthusiast and friend of good sound since a young age.

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