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Jon Hodgson · 1st July 2009

Dan,

thanks for that, perhaps you can give people here some more real world perspective on another aspect of conversion.

A repeating mantra of many people who either think that digital can never be good, or insist that sample rates should be as high as possible, is the one "there are no such things as perfect filters".

Now aside from the irony that this line so often comes from people who absolutely love analogue recorders, which are far from perfect in themselves, there seems to be little discussion as to how much things deviate from the theoretical ideal and how perceptible that is likely to be.

So, typically speaking, how imperfect are these filters? In what ways are they imperfect? How much are they affecting the passband? How much aliasing noise does imperfect attenuation in the stop band let through? How audible is any of this likely to be?

I think it would be good for people to get some perspective on the performance of real world anti-aliasing filters. I could try working out the numbers for myself, I know, but I'm sure you already did that, and of course you have the experience of how they actually translate to audibility in converters.

1st July 2009	#45
Jon Hodgson Lives for gear Joined: Jun 2009 Posts: 1,021 Verified Member	Dan, thanks for that, perhaps you can give people here some more real world perspective on another aspect of conversion. A repeating mantra of many people who either think that digital can never be good, or insist that sample rates should be as high as possible, is the one "there are no such things as perfect filters". Now aside from the irony that this line so often comes from people who absolutely love analogue recorders, which are far from perfect in themselves, there seems to be little discussion as to how much things deviate from the theoretical ideal and how perceptible that is likely to be. So, typically speaking, how imperfect are these filters? In what ways are they imperfect? How much are they affecting the passband? How much aliasing noise does imperfect attenuation in the stop band let through? How audible is any of this likely to be? I think it would be good for people to get some perspective on the performance of real world anti-aliasing filters. I could try working out the numbers for myself, I know, but I'm sure you already did that, and of course you have the experience of how they actually translate to audibility in converters.