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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

Showing 5 responses by garfish

garfish OP
1,840 posts
 
Sam...I agree with your post. Each of the manufactures implements this process differently, so they are going to sound different. BTW is HFNRR available on line? Cheers. Craig
garfish OP
1,840 posts
 
I would also like to add a short paragraph from Madrigal Audio's position paper on this subject that I recently got fom Madrigal's Todd Sutherland. This paper will soon be posted in it's entirety at www.madrigal.com. Quote: "So what's the point? The point is that "upconverting" digital audio to higher rates for conversion has been around , and in fact has been THE OVERWHELMINGLY DOMINENT WAY OF DOING THINGS, since somewhere between 1982 and 1984, depending on who you ask. Historically it has been called "oversampling". But whether you call it "oversampling", "upconversion", "upsampling" or anything else, it remains the same. It is a method by which the originally sampled data is converted to a higher rate for the purpose of better-quality conversion to analog." Because I ferreted out and posted these meaningful responses on this subject, do not consider me an expert-- I'm not. The conclusions of these responses agree well with what Greysquirrel got from Jeff Kalt of Resolution Audio and posted a few days ago. And sometime ago, a Theta Digital Rep. emailed me that their digital engineers considered oversampling and upsampling to be to be same thing. These industry leaders comments/positions have cleared up a lot of confusion about this subject in my mind. Cheers. Craig
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.
garfish OP
1,840 posts
 
Jordan; Thanks for posting your Jeff Kalt email, it adds a lot to this thread. Cheers. Craig
garfish OP
1,840 posts
 
Hi Treyhoss; It seems to me that you may be trying to "unscrute the unscrutable". Each of the components you mention would probably sound different from the others, and you would just have to try it to see if it provided any improvement. And then of course it would be in the context of the rest of your system. I personally think where these outboard upsamplers would be really worth while would be when used with less expensive CD players (as KH noted), but as the quality of the DA conversion process increases, the value of the outboard upsamplers becomes less important-- just my guess. I'm sure much of the technology used to actually build these components is proprietary-- whether they cost a few hundred dollars or thousands like the dCS gear. Cheers. Craig.
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