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Upsampling/Oversampling

I need some technical insight here. My Jay's Audio CTD3 Mk3 CD transport has the toggle switch for turning Redbook CD files into 4x upsampled (176.4kz) files. The dac being fed the files is a Holo May KTE. Holo Audio recommends keeping the dac in non-oversampled state all the time. The dac itself does no upsampling. The upsampling alone coming from the CD transport with dac in NOS mode makes for some very nice music, but I find I am liking the dac to be in oversampled (OS) mode when handling the 176.4 despite Holo recommending against it. In OS mode the detail, nuance, and air goes up a notch and voices gain more subtle inflection, and the music sounds a bit tubey and very pleasantly so. Problem is that after an hour or two of playing there will suddenly intrude pops and clicks that mandate stopping play.

I am assuming, perhaps wrongly, that the issue is that the dac's oversampling of already upsampled files is causing a mismatch of data processing that eventually catches up with and impedes proper data processing, and that the music feels more PRAT-y because there is some "euphonious distortion" that happens to sound "good."

After I have turned the CD transport off for awhile it can be re-started and all is well again when running the dac in OS mode - for awhile.

Any insights welcome.

bolong
carlsbad2's avatar
carlsbad2
1,723 posts
 

I think your problem has nothing to do with upsampling.

erik_squires
16,275 posts
 

The biggest changes with modern DACs in my hearing has been with the way the digital filter behaves, specifically the high frequency roll off.

With older DAC's I often found a very large gap in performance between 44.1/16 and higher resolutions but that's narrowed a lot since 2000.  That gap has really narrowed most recently. 

Personally I upsample my Internet radio and streaming music to 96/24 and can't hear any improvements after that.

mswale
121 posts
 

Just my thought. You are double oversampling? It might be overdriving the DAC when it starts to pop and click, it might be getting too hot? Think driving it like that for a long time will overheat it. The DAC is in overboots mode, receiving a very high signal to start, then it's trying to up convert that up-converted signal. The DAC chips will start heating up much more over normal use?

You can test, run the transport in normal mode, then upsample at the DAC, does it do the same thing? Reverse that with transport upsample, DAC normal. Does it pop?

 

bolong OP
636 posts
 

Yeah, something like that is what I was suspecting although it is over sampling an upsampled file. No popping when NOS is in place on the dac whether the file coming from the transport is Redbook or the transport has 176.4 turned on.

The fact that the popping is length of time played dependent certainly points a finger at overheating.

Strange though that Holo recommends leaving OS and OS PCM etc.off period. Why then are these modes even available at all?

Thanks

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