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Up & Over Sampling... Continued

I recently emailed Kevin Halverson of Muse Electronics and asked him for a short layman's description of the difference between digital over sampling and upsampling. Kevin designed the Muse Model Nine and two ninety six that are on Stereophile's Class A+ list, and he is one of the top digital designers in the business. His entire response of 08/11/00 follows: "Dear Craig; Over & upsampling are both Sample Rate Conversion processes (SRC). Both accomplish the same basic goal of increasing the sample rate to increase the image rejection. Neither has any inherent advantage over the other, assuming both are done in a synchronous and integer fashion. The basic differentiation is that upsampling is an external process, oversampling is an internal one. In the case of the Model Two Ninety Six or Model Nine, the internal rates are 352.8 kHz for CDs and either 354 or 768 kHz for DVDs. The present trend towards the use of "upsampling" devices is to improve the performance of poorer performing converters (those with inadequate image rejection). In the case of either the Two Ninety Six or the Model Nine, neither would benefit from any additional image rejection as both already have more than is necessary. I hope this will give you a small amount of insight to the process and all the marketing hype being thrown about. Best Regards, Kevin Halverson". Craig.
garfish
greysquirrel
62 posts
 
Treyhoss, don't forget the analog output section. You could have two digital systems with identical digital conversion processes and parts and they could still sound considerably better/worse/different because of how the analog section is implemented. As for the "synchronous and integer fashion", I'm not exactly sure what is meant by synchronous (though I'm very sure Kevin Halverson does). The integer portion just means that the oversampling should be carried out as an integer multiple of the incoming data rate (eg. 44.1 x 4 = 176.4, 48 x 4 = 192, 44.1 x 8 = 352.8, 44.1 x 16 = 705.6), not a fractional multiple. I'm kind of curious about the synchronous part. Anyone got an answer? Live the good life, Jordan
trelja
3,215 posts
 
Craig, many accolades are due you for getting down, and doing some dirty work. Of all the threads flying about this site, this is definitely one of the most educational I've read. Lots of good information here. Great job!
greysquirrel
62 posts
 
I agree with Trelja! Craig has kept it all together, adding knowledge and understanding through expert testimony along the way. Great job, Craig! And thanks for a copy of the Madrigal paper!! I love the title: "Upconversion and the Emperor's New Clothes".
treyhoss
287 posts
 
Hi Greysquirrel, I hear you loud and clear about the analog output section. I guess I was espousing my thoughts about what I was interpreting from Halverson's e-mail. I definately agree that there is much more than number crunching going on, hence the reason you have great players, lousy players and all points between. I guess I was just curious about these upsampling devices that exist out there and if they would bring a good D/A up to par with a great D/A costing much more $$. I certainly acknowledge the performance will only be achieved when/if all of the devices mate well together. -Tony
garfish OP
1,840 posts
 
Trelja-- thanks for the kind words-- just after the truth. And thanks to Greysquirrel for getting Jeff Kalt's thoughts on this thorny issue-- it was an excellent contribution and really started the "hunt". And it would actually be nice to have that post on this thread. It was really Jeff Kalt, Kevin Halverson, and Madrigal's positon paper that provided the "red meat" for us on this issue, so the biggest thanks goes to them for sharing their knowledge. Unscrutable-- whatever it was, I hope it was pleasurable rather than painful:). Cheers. Craig.
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