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Bit accurate sound from USB? - Page 3

post #31 of 32
Quote:
Originally Posted by RonaldDumsfeld View Post

A quick word to the wise mate.

In theory 'bit perfect' is best BUT if you are playing modern pop CDs you need to be aware of the effect of intersample peaks.

http://www.hometracked.com/2007/11/08/prevent-intersample-peaks/

http://www.cadenzarecording.com/papers/Digitaldistortion.pdf

You can test this yourself. Play a new CD at unity gain (volume slider on max.) and re record it with something like Audacity (again all sliders on max). Look at the resulting waveform. It'll quite often show clipping.

ASIO and related drivers were not originally written to move data around 'bit perfect'. They are designed to avoid windows kmixer and thus reduce latency. For instance when someone is trying to record a song and wants to add comfort reverb when monitoring. Usually when tracking (recording) you do so at well below max amplitude (up to -20dB) to avoid this problem and allow headroom for mixing. Then during the final mastering stage the complete tune is compressed to within an inch of it's life to obtain maximum volume.

Nothing wrong with using ASIO, KS or WASAPI if you want but I'd recommend setting the playback device to at least -3dB to be on the safe side and avoid the risk of clipping. It will not be strictly speaking 'bit perfect' but it will sound better.




It's good for reference, Thanks for your sharing!
post #32 of 32

Originally Posted by erozsolt View PostSo my rule of thumb:

 

- for a 16-bit DAC or a USB 1.1 solution only capable of transfering 16-bit music, I would just use KS/ASIO/WASAPI + no RG, no DSP, foobar volume 100%, windows volume 100%

- for a 24-bit DAC or a USB 2.0 solution capable of transfering 24-bit music, I would just use KS/ASIO/WASAPI and it doesn't matter what you do in a player or with the volume controls

 

 

It does matter,  and your math does not seem to make sense below either, let's take a look shall we?

 

Quote:

Originally Posted by erozsolt View Post

Mathematically you are right, but human ear is not resolving over 18-19 bit. And even in a high resolution music, the bits over 20 bit are mostly just noise. That's why for example on a 24 bit music, dithering has no effect because you are essentialy modifying the 24th bit, which no one can hear, or no equipment can really reproduce.

 

But my example was for listening Redbook CDs over 16-bit vs. 24-bit. If you listen to a Redbook CD over 16-bit and use a foobar volume control at 50%, then you have already reduced your usable bits to 15-bit! Thats a big difference, you can easily A-B test 15-bit vs. 16-bit.

 

Except for the fact that for every 6 db below 0db you loose 1 bit of resolution.  So for a volume control measured in db a -24 db setting will lose you 4 bits of resolution.  Now to check this, pull out a good 24 bit recording and play it at -24db on you player without dither and into a heaphone amp with an analog volume control.  Then play the same piece at 0db and adjust the analog volume control to give you the same overall loudness.  You will hear a difference albeit subtle on most system, but certainly audible by most folks used to using headphones.  Try solo violin with all its harmonics.

 

So you do not lose only 1 bit by reducing volume to 50%.;  But by using dither (which is what the itunes volume control does BTW) you will hardly notice any loss of resolution, just a smidge more noise.

 

for a good explanation try wading through this:

http://www.izotope.com/products/audio/ozone/OzoneDitheringGuide.pdf

 

http://www.digido.com/dither.html

 

If you do the same on a 24-bit equipment, then as a start you have 16-bit usable information and 8-bit with 0-s. If you apply a digital volume control in a 24-bit system, you only loose 1-2 bit from 24, not from 16, so essentially you will have a system capable of playing back 22-23 bit musical information, which is still way higher than what you can record/reproduce/hear, which is about 18-19 bit.

 

So you see if we do throw away resolution we do pay an audible penalty without doing something about it like dithering.

 

 

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