The apodizing filters really make the old cd's sound good, taking away the digital harshness. Robert Harley really likes the Meridian CDP's for this reason and called it "most significant CDP of all time" a few years back. I know Ayre and dCS also use them. Any great manufactures shunning them? Why would they not use them?
Any great digital gear not using apodizing filters these days?
- Thread starter caesar
- Start date
I don't know but suspect quite a few... Not sure they are really "shunning" them nor what constitutes "great manufacturers", but that aside here are some points to ponder:
1. Conventional linear-phase filters offer good impulse response but by nature are symmetric in the time domain, which leads to the oft-discussed "pre-ringing" that happens as a result of making them causal. Non-casual filters, well, we haven't quite solved those yet, maybe after we get the warp drive.
2. Conventional filters already live in a lot of units and many folk do not seem to mind them. Of course, they may not know better… Manufacturers may stick with what works.
3. With oversampling DACs and better up-converting algorithms, you can move the filter’s corner up and reduce the roll-off, significantly reducing the ringing linear-phase filters add.
4. Apodizing filters add some pretty severe ringing of their own, and I wonder if the relatively large post-ringing isn’t as annoying as low-level pre-echoes but do not know.
5. A combination of apodizing and linear-phase, with or without oversampling, would seem to be the ideal solution to me. Assuming no oversampling, you’d get a bit of phase shift at the highest frequencies, a little more roll-off at say 18 - 20 kHz and up, and the advantage of the quasi-brick-wall linear phase filter by Nyquist (about 22 kHz for CDs or other 44 kS/s systems).
FWIWFM - Don
1. Conventional linear-phase filters offer good impulse response but by nature are symmetric in the time domain, which leads to the oft-discussed "pre-ringing" that happens as a result of making them causal. Non-casual filters, well, we haven't quite solved those yet, maybe after we get the warp drive.
2. Conventional filters already live in a lot of units and many folk do not seem to mind them. Of course, they may not know better… Manufacturers may stick with what works.
3. With oversampling DACs and better up-converting algorithms, you can move the filter’s corner up and reduce the roll-off, significantly reducing the ringing linear-phase filters add.
4. Apodizing filters add some pretty severe ringing of their own, and I wonder if the relatively large post-ringing isn’t as annoying as low-level pre-echoes but do not know.
5. A combination of apodizing and linear-phase, with or without oversampling, would seem to be the ideal solution to me. Assuming no oversampling, you’d get a bit of phase shift at the highest frequencies, a little more roll-off at say 18 - 20 kHz and up, and the advantage of the quasi-brick-wall linear phase filter by Nyquist (about 22 kHz for CDs or other 44 kS/s systems).
FWIWFM - Don
Thanks, Don. I would call great digital anything that appears on the Stereophile recommended list as class a or class a+ ( or whatever the uber class A is called).
To my ears, the difference between the filter and no filter is obvious: there is less "smearing" of instruments and they are better separated in space. There is also less noise so one can hear more details and a better musical flow. In essence, the red-book recordings sound like they hi-rez, and the awful, older CD's become more enjoyable. The better the player, the more quiet the background becomes, and the acoustical space becomes more three dimensional.
The measurements are pretty straight forward, as explained in plain language by this white paper:
http://www.ayre.com/pdf/Ayre_MP_White_Paper.pdf
To my ears, the difference between the filter and no filter is obvious: there is less "smearing" of instruments and they are better separated in space. There is also less noise so one can hear more details and a better musical flow. In essence, the red-book recordings sound like they hi-rez, and the awful, older CD's become more enjoyable. The better the player, the more quiet the background becomes, and the acoustical space becomes more three dimensional.
The measurements are pretty straight forward, as explained in plain language by this white paper:
http://www.ayre.com/pdf/Ayre_MP_White_Paper.pdf
Hmmm... I do not know of any DAC unit that has no filter. The two or three I have managed to find any details on that claim no filter do have filtering, just not the usual kind. I strongly suspect the differences you hear are not due to the filter, or at least not that alone, but also better circuitry inside the player that lowers the noise floor etc. I have not heard a unit with both types of filters so cannot say for sure. - Don
* Skimmed the paper -- seems I guessed rightly, if we agree the Ayre is a good unit.
* Skimmed the paper -- seems I guessed rightly, if we agree the Ayre is a good unit.
I agree about the better circuitry and parts, but seems like everyone "in the expensive price point" is jumping on the filter bandwagon also. Meridian pioneered them. Ayre followed. dCS has them also. I just found this on the Meitner site for their top of the line player, which has a figure that is very similar to what Ayre published in their white paper.
http://www.emmlabs.com/pdf/XDS1_brochure.pdf
http://www.emmlabs.com/pdf/XDS1_brochure.pdf
I had Ayre CD5xeMP. A very good CDP but out of curiosity and Robert Harleys statement I bougth the The Meridian CDP used. What a disapointment! The sound was "correct" but lifeless and dull. I sold it!
I finally settled for the Nagra CDP. The best CDP I hav ever tried.
I finally settled for the Nagra CDP. The best CDP I hav ever tried.
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