Comparatively, we see that DSD Master is using a form of minimum phase filter that removes the pre-ringing but the post-ringing is augmented.ĪuI ConverteR is an interesting case. JRiver looks like it uses an intermediate phase filter (with 24kHz or 30kHz low-pass) which minimizes but does not remove pre-ringing. Whereas AudioGate allows high frequencies through (and thus well formed impulse), we see the effect of Saracon's filter (pre- and post-ringing ~30kHz). Both use linear phase filters with characteristic symmetrical pre- and post-ringing. When we use iZotope RX 4 with 30kHz low-pass filtering (4th left image from the top), the "impulse" amplitude is significantly reduced and we see the corresponding ringing pattern as the high frequency noise is removed and no longer obstructing the picture.ĪudioGate and Saracon both look very similar. The shape and timing of the impulse would be completely retained since the 2.8224 MHz sampling rate of DSD64 provides ~29 samples within each 96kHz time period. From a time domain perspective, the SACD conversion process is excellent. Notice again the amount of noise in the signal and again, we see the superiority of DSD128. When I convert this waveform to DSD64 and DSD128 with Saracon and then back to PCM with the foobar SACD plug-in to 24/352 unfiltered (retaining all that ultrasonic noise), you get the 2nd and 3rd left images. Even though Adobe Audition renders the interpolation, the actual PCM data itself is a simple, single "pulse" (see Addendum below for screenshots using Audacity). In the top left panel, this is what a 0dBFS 24/96 "impulse" would look like with a typical linear-phase oversampling interpolation showing symmetrical pre- and post-ringing. Let's see what a 24/96 impulse looks like after going through the DSD encoder and most of the decoders I looked at (DSD-to-PCM converter output set to 24/352 for each, AudioGate's max was 192kHz): The question is, just how much noise reduction should we actually do? (You can also see the noise through an analogue oscilloscope - as shown here.)Īs noted by Juergen in the comments to the previous post, there is this matter about time-domain behaviour as well which can be skewed as we apply various filters. Notice that DSD128 is significantly less noisy. This is what all that extra high-frequency noise looks like in DSD when you don't filter it out at all. If you feel there is no need to retain frequencies >20kHz, then this will clearly get the job done.īut wait, there's more! SACD Plug-in also has a 30kHz lowpass mode - "Direct - (Double Precision, 30kHz LF)". This is done with a very strong low-pass filter. The AuI ConverteR software puts up some impressive numbers. I would not be surprised if the algorithm (DSD2PCM) is essentially the same if we look "under the hood".Ģ. foobar SACD plug-in works about the same as the old DSDIFF plug-in. Otherwise, foobar DSDIFF and the newer SACD plug-ins appear very similar.īasically, this is what we can say at this point.ġ. That little bit of high-frequency "rippling" with DSDIFF is probably a result of the resampling algorithm. That is an impressively sharp, precise filter at 20kHz! I can approximate that effect with iZotope RX 4's EQ plug-in with a low-pass at 20kHz, high Q of 25 or so (not shown) but AuI ConverteR looks even cleaner with less noise floor irregularity.
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