Pre-ringing is minimal in comparison to the top image. There is a little bit of noise that seeps through but really quite minimal and overall a nice compromise. As discussed before, it uses a ~30kHz filter. The second image is the nastiness of DSD64 noise without any filtering at all (from the foobar SACD plug-in).īelow that is Saracon DSD64 decoding. The spectral display demonstrates nicely that the "ringing" is at the Nyquist frequency 48kHz. With a standard PCM impulse run through a typical sharp linear antialiasing filter, we get the top image. The spectral frequency display also beautifully demonstrates to us how the impulse response differs for each of the DSD-to-PCM decoder programs. (For practical reasons as I really don't think we need to concern ourselves with noise >96kHz, each case was analyzed at 192kHz instead of the maximum 352kHz output from the DSD decoders.) DSD64 with 50kHz (simulation of the default Sony SCD-1 / SACD player filter) isn't bad but obviously we see the noise >20kHz breaking through a bit and if you click on the image and look at the sine wave closely, it's not hard to see a few "imperfections" from going through the DSD64 encoding stage. Of note, the DSD128 conversion with a 50kHz filter looks pretty good. In each of the spectral frequency plots, we see the bright yellow 10kHz signal as well as any noise within the spectrum up to 88kHz for the 176kHz PCM, and 176kHz for the DSD conversions done at 352kHz. Overlaid are the 3 typical views - waveform itself, FFT frequency analysis, and spectral frequency display using Adobe Audition:
I know a few people on audiophile forums suggest they subjectively preferred the filter be turned off.Īnyhow, here's what a simple 10kHz PCM sine wave originating as 24/176.4 would look like after being converted to DSD64 and DSD128 (again with Saracon) and then decoded back either totally unfiltered with foobar2000 SACD plug-in and also if we applied a 50kHz low-pass filter with iZotope RX 4. Well, I don't know about the formal standards, but the first Sony SCD-1 SACD player back in 1999 had a defeatable analogue filter placed at 50kHz and according to the DSD Wiki, all SACD players were supposed to include this "optional" filter. Also, Mnyb talked about the low-pass filtering in SACD players and what "standards" were used. I was reminded recently by Wombat in his post here that we can have a look at the spectral frequency display as well when assessing sonic data in the audio editor.
It refers back to the DSD-to-PCM analysis series from April:ĪNALYSIS: DSD-to-PCM Conversion 2015 - Windows & Mac OS XĪNALYSIS: DSD-to-PCM 2015 - foobar SACD Plug-In, AuI ConverteR, noise & impulse response.Ĭonsider this as part 3 of the 'trilogy' for this week as I continue to work on the results of the recently-closed Digital Filters Test. As happens sometimes, a post can get lost in the "draft" bin and later found. Okay guys, I actually wrote the text that follows 2 months ago before the Digital Filters Test.
A cool example of the "Spectral Frequency" display - from Adobe.