Digital Drive

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I was not looking to get into a discussion about NOS versus Delta sigma. But that is okay and educational as well. Just wanted to know what improvements people are hearing when they upgrade. For example Holo Spring to Holo May DAC.

Here is an interesting read:
"Before I go any further, perhaps a brief primer on digital filtering is in order. According to the vast majority of the audio industry, accurate Redbook 16-bit/44.1kHz playback requires some sort of filter to attenuate if not completely eliminate mirror images that result from the D-to-A conversion process. These reflections occur on either side of the 44.1kHz sample rate and its harmonics. Supposedly, these spurious images, if left untouched, may cause very audible colorations and distortion, not to mention a great deal of difficulty for certain partnering amplifiers and loudspeaker tweeters. Incidentally, techniques such as oversampling and upsampling are extremely helpful tools in suppressing this digital noise. They push this racket into ultrasonic frequencies to allow shallower, less aggressive reconstruction filtering. Or so the theory goes. A small minority believes that these filters are less than desirable for audio use. The effectiveness of the filtering action is linked to a ringing on both sides of the impulse peak of each 16-bit sample. Apparently, it is this pre and post echo or ringing bracketing the signal's impulse that is cause for concern since half of it occurs actually prior to the musical event. Unfortunately, the degree of echo is directly proportional to the effectiveness of the digital filter, i.e. the more effective the filter is in reducing reflections, the more ringing will occur. Naysayers of conventional filters believe this pre-echo smears the signal in the time domain to adversely affect imaging and more importantly, rhythm or pace.


This is interesting. I find Redbook gear in general to be more or less lacking in the foot-tapping department when compared to vinyl. By removing the digital filter altogether; the impulse response is essentially perfect, without pre or post ringing. However, digital mirror images are free to run amok. This may cause audible (and certainly does cause very measurable) colorations. Some proponents of this topology such as Zanden use proprietary analog filters after the D-to-A process to attenuate this spuriae but that approach is very costly and will probably not trickle anytime soon into more budget-orientated products. Whether one chooses a filtered or non-filtered design will likely involve accepting distortion of one kind or another. Neither process is perfect but then, what else in life ever is? You just need to pick what's right for you. However, while the great majority of manufacturers believe suppression of spurious digital images is of paramount importance, it is interesting to note that some clever souls utilize additional circuitry alongside their oversampling digital filters in an attempt to reduce pre and post ringing. The filters used in Pioneer's Legato Link players are one example. Perhaps this ringing distortion is important to address after all.



Edits: 11/16/23

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