By Lam Seng Fatt
In January this year, leong2013 posted this question in hifi4sale: “Does DSD have a role in high-end audio, and if so, what is it?”
The simple answer is: “Yes.”
The complex answer is: “It’s complicated.”
I shall try to explain the complicated answer in a simple way.
All audiophiles, music lovers and anyone who has played a CD (from the late 1980s) would have heard DSD in action. Though DSD is all the rage now, it is actually not new. Confused? See, I told you it would be complicated.
In most DAC (Digital to Analogue Converter) chips, the PCM data in a normal CD is converted to DSD format before being converted to an analogue signal. So if you have played a CD before, you would have heard DSD in action.
In the case of dCS, its proprietary DSD signal processing and dCS Ring DAC oversamples all incoming data to 5 bits at 2.822 or 3.07 MS/s. dCS converts everything it receives into the DSD domain. Therefore, if you have heard a dCS DAC before in a showroom, a friend”s house or an AV show, you have already heard DSD.
And also, DSD can also be found in SACD discs, which have DSD files with special encoding so that they can only be played on SACD players. So if you have heard SACDs being played before, you have heard DSD.
To understand the relationship between PCM and DSD, you have to understand the history of CDs and digital music, and the work done by Sony and Philips.
Check out DSD – The New Addiction by Andreas Koch http://dsd-guide.com/dsd-new-addiction-andreas-koch
Andreas was pivotal in the development of DSD and also the DoP (DSD over PCM) protocol via USB which is used by all the DSD-capable DACs in the market today. He is also the owner of Playback Designs which makes high-end DACs and SACD/CD players.
He writes: “The term Direct Stream Digital (DSD) was coined by Sony and Philips when they jointly launched the SACD format. It is nothing else than processed Delta-Sigma modulation first developed by Philips in the 1970s. Its first wide market entry was not until later in the 1980s when it was used as an intermediate format inside A/D and D/A converter chips.
“Delta-Sigma modulation: the analog signal is converted directly to DSD with a very high sampling rate. Various algorithms are in use depending on the application and required fidelity. They can generate 1-bit DSD or multibit DSD oversampled at 64x or 128x compared to regular CD rate.
“Decimation filter: the DSD signal from the previous step is downsampled and converted to PCM. Word length is increased (for instance 16 or 24 bits) and sample rate reduced to CD rate or a low multiple of it for high resolution PCM formats.
“The D/A process is very similar where: the PCM signal is upconverted to a much higher sample rate.
then converted to DSD via the Delta-Sigma modulator (to reduce word length) then converted to analog.
This technology was chosen because of its improved linearity and consistent quality behavior across physical components, as most of the heavy duty signal processing was shifted to the digital domain where it was not susceptible to variability of electronic components. It was quickly adopted in most converter systems and we can say that since about the late 1980s we have been listening to some form of DSD without even knowing it.”
DSD downloads
To add to the complicated situation that DSD is in, the majority of DSD dowloads are not true DSD files. They are merely analogue or PCM files converted into DSD.
AFAIK, the only true DSD files – recorded in DSD and sold as DSD downloads – are from Blue Coast Records http://bluecoastrecords.com/free-downloads. Even 2L records in 24/352.8 PCM to be converted into DSD.
Most songs in the digital age were recorded in PCM because it is easier to do editing in the PCM format since the 1-bit DSD files are extremely difficult to edit.
Some of the DSD downloads of older songs recorded in the 1960s-1970s are remastered from analogue tapes. Therefore these cannot be considered true DSD files. Some audiophile recording companies like opus3 http://www.opus3records.com/ record in analogue.
There are several products that can perform DSD recordings from companies such as Korg, Pyramix, Desono (formerly Genex Audio), Sonoma and Meitner, but these are more expensive than the popular Pro Tools software which records and edits only in PCM.
Coming back to leong2013’s question, the answer is “Yes.” In fact, DSD has played a role in high-end audio since SACDs were launched in 1999. And it has played a role in consumer-level audio since the 1980s.
