upscaling, bits and resampling ??

Read my test report on forum in a new post titled Upsampling Put To The Test...it should show up there later today. Look when you have some time, it's a long article! :-)

Zaikesman, I'm stuck for now with old machines EAD DSP7000 MKII and Monarchy DT 40b as a transport. I'm also curious what units you're going to a/b.
I'm aiming to keep transport but upgrade the DAC and the best so-far I've heard is TACT RCS(pre-amp with DAC)

If I'm not mistaken, I believe that the multiple concurrent sampling technique that Marakanetz and Jeff refer to above is actually descriptive of *oversampling*, rather than "upsampling", which has more to do with Jeff's reference to the use of alogrithmic interpolation to synthesize "extra" samples in between the data points to "smooth" the sampling frequency. Both of these are distinct from the adding of extra bits of random dither to "extend" word length from the 16-bit CD data to 24-bits before it is fed to the DAC chips, which is done in an attempt to better linearize the chips' low-level performance. Again, to the best of my (admittedly limited - thanks, Sean!) knowledge, neither of these techniques can actually increase the resolution of the recreated analog signal, but are efforts to extract more subjectively pleasing results out of the digital-to-analog conversion proccess. (I do promise to read that link, Sean - I hope it doesn't show me to be too far off base here!)

I will add that I recently bought a newer generation, popular "upsampling" DAC to audition against my well-regarded older unit, which does only tradtitional oversampling. While I found that upsampling did indeed change the sound, I contucted a controlled test which informed me that - at least for this particular DAC - the results were actually less faithful to the digital input signal it was being fed when upsampling was engaged than when it was defeated. I also wound up preferring, and finding to be most accurate, the performance of my reference model. I intend to write a full review of these sessions and post them separately here on the forum soon, but this experience did once again drive home the fact that it's not the type of technology used, but its implementation, that will often make the biggest difference in performance.

Besides having less chance for error, Upsampling systems often have processors doing algorithmic interpolation, dithering, etc. that will add some additional information in between the digital 'spaces'. A well implemented one will reduce the size of the digital 'stairstepping', so that the 'steps' are much closer together, and therefore smoother & less 'digital sounding', being closer in nature to analog.

Jeff

Zaikesman is spot on ... ignore the hype and use your ears. If you're interested in how it works go to DCS's web site http://www.dcsltd.co.uk/papers.htm. Beware of answers on Audiogon, because it is my experience that many people offering answers don't really know what they're talking about.

To be strictly theoretical the number of bits represent an amplitude. Thus for red-book CD the 16th bit represents the highest amplitude. There also the number of samples that divides the audiable freequency spectrum 20Hz...20kHz. 44.1kHz is the sampling rate of the red-book CD. Any represented analogue audiable signal can be placed in the grid of bits and samples.

Imagine that you want to make a copy of the picture and you drow the grid on your empty piece of paper and you drow the same grid on the picture and start re-producing exact copy.
The same thing happens in digital recording. The more density grid the more precise "picture" you will be able to drow.

So finally if you want to know what realy upsampling and upscaling can do:

Upsampling is simply increasing the sampling freequency. It decreases the overall probability of error. One sample from red-book CD decoded by upsampled 192kHz DAC will be decoded by ~4 samples. The resulting probability of error of 4 samples at the same time is much smaller than the probability of error of pure 1 red-book sample.

Upscaling basically will not change even a thing for a red-book CD placing the same way 16-bit amplitude into 20 or 24-bit amplitude. It might only benefit HDCD if coding is present and higher mastered CDs.

New tech made it easier to perform the reading with minimal error in comparison to the older machines but still "former heavy weight digital champs" sound great -- do your research and deside.

That was really helpful, thank you....

Different companies have different engineering approaches to how to get the best sound from CD. Regardless of what approach is used, no more information than the 16 bit/44.1KHZ data density that is on the disk itself can be extracted or manufactured by any player.

Beyond that, all I can say is that upsampling, oversampling, straight sampling, multi-bit data conversion, one-bit data conversion, increasing word bit length, reclocking jitter-reduction, data buffering jitter-reduction, adjustable dithering, aggressive filtering, gentle filtering, no filtering, adjustable filtering, single-ended DAC topology, differential balanced DAC topology, active current to voltage conversion, passive current to voltage conversion, S/PDIF input, AES/EBU input, proprietary input configurations, balanced output, single-ended output, tube-buffered output stages, transistor-buffered output stages, etc. - they all have their proponents and detractors. But it is possible to build a good- or bad-sounding DAC or player using just about any of these approaches.

The quality of the implementation is as important as the design approach. This also includes such mundane concerns as transport and laser mechanism, power supply, sheilding, parts quality, mechanical isolation, and even the display readout and remote control. So try to audition some components within your budget that you are interested in with your own system (or at least try to hear them at a shop or a friend's place), and remember that sonic differences between digital components are often subtle in nature compared to, say, different speakers or amplifiers, so be prepared to listen at length, and try to to do direct level-matched comparisions if possible.

I wish there was a way I could tell you what specific configuration to look for that sounds the best, but it just doesn't work that way, so don't get too hung-up on the buzzwords and technical jargon. (Also, beware of players that "make all disks sound good" - lots of CDs actually don't sound that good, but a player that euphemizes the sound too much rather than telling you the truth will impose a sonic signature on all your disks that will eventually become wearisome. And good power conditioning and cords often help digital front ends the most of any sources.) Your ears will know!

P.S. - Take into consideration whether you will want a machine that can decode formats other than regular CD when choosing your player or DAC of the future.