As I said yesterday, thanks to my friendship with Jim Merod of BluPort Records and the generosity of Dr. David Robinson of Positive Feedback Online, I was allowed to contribute my thoughts on DSD during the T.H.E. Show Newport Beach session entitled “DSD Downloads From The Studio To Your Home”.
Jim, of course, knows that I’m not an advocate of the format for production OR distribution. In the few minutes that I held the floor from the back of the seminar room, I focused on a few carefully researched items.
The first is the complete lack of production tools that are available to work natively in the format. DSD was originally developed by Sony and Phillips as an archiving format. They never intended DSD, in any multiple, to be used by recording engineers to do new productions. Once the SA-CD format was launched, the engineering teams realized that DSD as a native 1-bit system was incapable of being used like the DAW (Digital Audio Workstations) for any postproduction work. You couldn’t mix, you couldn’t edit, and you couldn’t modify the timbre or dynamics of a 1-bit stream. Jared Sacks from Channel Classics confirmed that in his videotape presentation during the DSD session on Saturday. He moves to DXD whenever he needs to do postproduction work on his native recordings.
Instead, the production flow in DSD requires a different approach. The Sonoma DSD multichannel recorder can be used as a simple recording deck with great quality analog to digital and digital analog converters on the front and back. This means that the engineers simply capture the output of the ADC during the sessions. To do any of the post processing, they send the DSD DAC signal to a large analog console. There are lots of classic and modern consoles that have wonderful equalizers and dynamics processors as well as faders to adjust the sound. If reverberation is needed (and it usually is for jazz and commercial releases), for example, then the analog signals are sent to PCM-based signal processors, reconverted to analog and mixed into the final stereo mix.
A second alternative involves converting the DSD 1-bit native streams into DXD. It turns out that there are lots of well-developed tools for DXD. You can change the equalization, modify the dynamics, edit and normalize in DXD quite easily. DXD is simply another name for High Definition PCM! This version of PCM runs at 352.8 kHz and captures 24 or 32 bit words. It is one of the highest resolution recording formats on the planet (only 784 kHz/24 or 32-bit PCM is higher). In fact, as I pointed out, my friend Morten Lynberg at 2L uses DXD to record ALL of his projects and then downconverts to 192 Khz/24-bit FLAC or DSD 64. This makes sense to me and I said so at the DSD session. Morten’s methodology represents that third production option.
As I closed my comments, I mentioned the session that I was involved with in Montana. I wrote about that unique opportunity some weeks ago (see post here). Brett Allen, who owns SnowGhost Studios in Whitefish, Montana invited a few select engineers to his studio in late March to do some critical listening and to participate in a comparison between a recording done on analog tape (2″ Studer A827), Sonoma DSD 64 with Meitner conversion and PCM at 96/24 using Mytek conversion. My statement to the assembled Newport crowd highlighted the fact that both the DSD and the HD PCM sounded really wonderful…especially as the amps and speakers were worth more than $250,000 (Wilson and VTL…Peter McGrath and Luke Manley were in attendance)!
However when I looked at the spectragraphs of the mixes done through DSD vs. PCM, I saw the normal pattern of “ultrasonic” noise associated with the DSD plot. The PCM ultrasonics were pristine and showed the expected blackness at 20 kHz and higher. The left side of my brain believes this is problematic and makes DSD unusable…and I’m not alone in my position. I mentioned that Jonathan Reichbach, the owner and programmer of Amarra, John Siau of Benchmark, James Tanner of Bryston and Robert Stuart of Meridian agree with this position and have no plans to implement DSD in their products. The advocates of DSD ignore this and focus on their right brain reactions (the emotional/creative half). See the figure below.
Figure 1 – A comparison of the spectra of DSD vs. PCM. Click to enlarge.
There is lots of uncorrelated high frequency noise associated with ALL flavors of DSD. It doesn’t matter whether you use DSD 64, 128 or 256 or whether you “upconvert” standard DSD to higher versions…you will still have noise that must be shifted. It’s true that it can be rolled off leaving the remaining 20-20kHz clean and completely useable. And if capturing and reproducing sound above 20 kHz is meaningless, then DSD can be a wonderful format.
But for someone interested in expanding the realism of audio recording by maximizing both the dynamic range and frequency response of a recording, DSD is a non-starter. I prefer a methodology that lacks the noise and inaccuracies of DSD… and I’m not alone.