Axiom Home Page Forums General Discussion Technical Questions upsampling (not oversampling)

I recently purchased a Philips dvd 759sa dvd player which plays sacd's as well as red book cd's.For playing cd's your given the option of using the regular cd sampling rate as well as upsampling of 88.2hz/24bit or 176.4hz/24bit up sampling (not oversampling).Either my hearing is off or this is all a bunch of hogwash,but I don't hear an iota of difference between any of these formats.Iv'e noticed various upsampling dacs on sale for over a thousnd dollars.Is this a ripoff or is it just my hearing ability? There's so much b.s.going on out there in the so called highend audio market that it's difficult to differentiate beetween the truth and hype. Has anybody out there have experience with upsampling?

Arthur, in this case your ears have been giving you the true story; upsampling reaches no different end result than does the oversampling process which all CD players have used for over 20 years. The 44.1KHz sampling rate of CDs can't be increased with more "real" samples than were originally present, but oversampling/upsampling mathematically inserts dummy samples in between each actual sample. Not going into full detail, this artificial higher sampling rate permits the use of a gentler filter to remove the harmful frequencies above the Nyquist Limit of 22.05KHz(half of the 44.1KHz sampling rate), avoiding bad effects from a very steep filter which would otherwise be necessary. Upsampling just divides the process of inserting the dummy samples into two steps by adding the upsampling stage before the regular DAC(which typically does 8x oversampling by inserting 7 samples for each actual one). The up and over sampling divide the work and reach essentially the same result as the oversampling DAC would reach by itself. Although the usual fanciful reports of huge benefits can be read, this is nonsense since nothing has been changed and it's still the same 44.1KHz sampling limit of the CD format(which is, of course, plenty for human ears). Some comments on this by Charles Hansen can be read here .