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Is "bit perfect" something I need to worry about?

post #1 of 9
Thread Starter 

I'm an absolute novice with computer audio (and really all audio for that matter).  I've recently begun researching high quality headphones.  That search inevitably lead me to discover the need and advantages of headphone amplifiers and dedicated DACs.  The Schiit Magni + Modi combination is looking good to me, perhaps paired with the HD598 headphones.  I've learned a lot in my research, but there are a couple concepts I'm still hazy on.  Hopefully you guys can straighten me out.

 

1. Aside from hooking my Modi into the computer's USB input and selecting it as the output method, is there anything else I'll need to do to bypass my computer's onboard DAC and ensure the Modi's doing all the work?  And how do I actually verify that the onboard DAC is being bypassed?  I'm running Linux Mint 16.  Sound card is integrated (ASRock Z77 Extreme4 motherboard).  

 

And the concept that I'm most confused about:

 

2.  "Bit perfect".  What exactly is it, and is it something I should care about?  Will the quality of my music suffer if I neglect this?  I'll be listening to CDs and FLACs.

post #2 of 9
Quote:
Originally Posted by caiman View Post
 

I'm an absolute novice with computer audio (and really all audio for that matter).  I've recently begun researching high quality headphones.  That search inevitably lead me to discover the need and advantages of headphone amplifiers and dedicated DACs.  The Schiit Magni + Modi combination is looking good to me, perhaps paired with the HD598 headphones.  I've learned a lot in my research, but there are a couple concepts I'm still hazy on.  Hopefully you guys can straighten me out.

 

1. Aside from hooking my Modi into the computer's USB input and selecting it as the output method, is there anything else I'll need to do to bypass my computer's onboard DAC and ensure the Modi's doing all the work?  And how do I actually verify that the onboard DAC is being bypassed?  I'm running Linux Mint 16.  Sound card is integrated (ASRock Z77 Extreme4 motherboard).  

 

And the concept that I'm most confused about:

 

2.  "Bit perfect".  What exactly is it, and is it something I should care about?  Will the quality of my music suffer if I neglect this?  I'll be listening to CDs and FLACs.

 

1. Normally you can have just one default audio output device selected ... if you select the output device through your playback software then it (selected device) is dedicated for that output only (when it's not set as system default as well).

 

2. "Bit perfect" output means that the original digital data is not changed while sent to your output device (DAC) --> use of EQ or other DSP is not allowed. Some O/S has two type of signal paths to offer ... one that might change the data (src, dsp) and the other which does not change the data. People caring 'bout bit perfectness usually uses the latter option. Dunno which path the CD playback uses (if it does not go through some dedicated software) but, good playback software lets you select both type output paths.

post #3 of 9
Thread Starter 

Thanks.  So I've followed the instructions in this thread for setting up Gmusicbrowser to output via ALSA.  I know my music is definitely outputting through ALSA because I can run killall pulseaudio and I still get sound from Gmusicbrowser but nowhere else.  But what I'm still unsure of is this:  how can I actually verify that my audio output is bit perfect?  This may be more of a Linux specific question, but is there a way to actually see first hand that my audio isn't being processed, or do I just have to assume?

post #4 of 9
Quote:
Originally Posted by caiman View Post
 

...

 But what I'm still unsure of is this:  how can I actually verify that my audio output is bit perfect?  This may be more of a Linux specific question, but is there a way to actually see first hand that my audio isn't being processed, or do I just have to assume?

 

Maybe you find help for testing the bit-perfectness from this thread: http://www.head-fi.org/t/81595/test-sound-file-for-bit-perfect-playback

post #5 of 9

Stop worrying about it. I'd be very surprised if you could actually hear a difference.

post #6 of 9

Nothing you should be concerned about, unless you're a total perfectionist and an avid audiophile/musical purist. You'd really need top notch equipment to clearly hear the difference, and even then you might wonder if it's all a placebo effect, or if it's real.

post #7 of 9

If you want to verify you must do a null test.

You record the digital out of the PC, load the file and the recorded file in an audio editor, time align and subtract the tracks.

If you end up with a file with only zero’s you know input and output are bit identical.

 

Some simple tests

If your DAC has indicators for the sample rate, play files with a different sample rate and your DAC should switch sample rates as well.

This won’t tell you if there is some DSP like dithering going on but at least no resampling is taken place.

 

Don’t know how ALSA works but in case of Windows/WASAPI exclusive mode, the path between the media player and the audio device is bit perfect. Hence if you play something that didn’t match the properties of the audio device, e.g. a sample rate not supported by the input of the DAC, it raises an error. If it plays, somewhere some resampling is going on so not bit perfect.  

Again this won’t tell you if there is some DSP like dithering going on but at least no resampling is taken place.

 

post #8 of 9

Try cat /proc/asound/card1/stream0

This will tell you the current sample rate

Again this won't tell you if there is some DSP going on

post #9 of 9
Quote:
Originally Posted by gyzimaki View Post
 

Nothing you should be concerned about, unless you're a total perfectionist and an avid audiophile/musical purist. You'd really need top notch equipment to clearly hear the difference, and even then you might wonder if it's all a placebo effect, or if it's real.

Using senheisser's hd598 with asus xonar d2 I can't notice any difference, so I don't worry about.

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