[regal]

Download a test tone generator. Just google search for one, Soundgen is freeware.

Now play tones thru your NOS DAC. Go up to around 14khz, keep going up and notice the tones geting lower in pitch?

The aliasing in these NOS filterless designs turn 15khz tones into ~10 khz, basically skewing your upper treble down 5khz. They are very inaccurate.

 

[Mrjabba]

Quote:

Originally Posted by regal /img/forum/go_quote.gif Download a test tone generator. Just google search for one, Soundgen is freeware. Now play tones thru your NOS DAC. Go up to around 14khz, keep going up and notice the tones geting lower in pitch? The aliasing in these NOS filterless designs turn 15khz tones into ~10 khz, basically skewing your upper treble down 5khz. They are very inaccurate.

will try soon

but my NOS dac sounds sooo good even if inaccurate

 

[d-cee]

maybe that's why many observe they have rolled off highs?

 

[Turn&cough]

Would you say that rolled off highs translate into less detail or just less aggressive treble?

 

[Jahn]

"if it sounds good, it is good." frequency thingies make my brain hurt! *hugs his DAC-ah*

 

[Max F]

Don't forget the effect of your own ears at this high freq! You may not be hearing correctly above 15 khz. Just keep that in mind too.

 

[Dept_of_Alchemy]

Quote:

Originally Posted by regal /img/forum/go_quote.gif Now play tones thru your NOS DAC. Go up to around 14khz, keep going up and notice the tones geting lower in pitch? The aliasing in these NOS filterless designs turn 15khz tones into ~10 khz, basically skewing your upper treble down 5khz. They are very inaccurate.

Are you sure that it's not just a consequence of the equal loudness contour? If you turn the volume way up, you might notice less roll-off because our ears are more linear at louder volumes. Do you have a reference for the anti-aliasing claim? I understand that filter designs vary quite a bit from DAC to DAC (3-pole, 5-pole, etc).

 

[Alleyman]

No, if the tones are actually aliased into ~ 10 Khz tones then they will be "louder" or the same volume to the human ear. Pitch != volume, so this is a good test.

 

[Absorbine_Sr]

Quote:

Originally Posted by Jahn /img/forum/go_quote.gif "if it sounds good, it is good." frequency thingies make my brain hurt! *hugs his DAC-ah*

Amen brother.

A_Sr.

 

[regal]

Its not the the frequencies above 15k are roll-off, they are converted into a lower pitch. This has been verified with a mic/spectrum analyzer.


Take the test to hear what I mean.

 

[infinitesymphony]

Doesn't every DAC need some kind of low-pass filter?

Are oversampling and filtering techniques tied together? I understand that having a brick wall low-pass filter would ruin the high-frequency response, but how does a no-filter DAC work?

 

[mcsamms]

I have done a similar test with my set-up. But I have some audio editing software that I just create whatever frequency I want to test for. With my dac I can hear up to 19khz but after that, I figure either I just can't hear the tones or the background noise (computer fan, external hard drive) is too loud to distinguish anything above that. Either way I do not find the sound does anything but get really annoyingly shrill. To be honest 19khz is a bloody annoying sound, not sure why someone would want to hear it crystal clear.

 

[otakukage]

very interesting thread

 

[Herandu]

Quote:

Originally Posted by infinitesymphony /img/forum/go_quote.gif Doesn't every DAC need some kind of low-pass filter? Are oversampling and filtering techniques tied together? I understand that having a brick wall low-pass filter would ruin the high-frequency response, but how does a no-filter DAC work?

Spot on! The problem is that even the DAC chip manufacturers' data sheets tend to give examples of multiple low pass filters on oversampling DACs that are designed for NOS DACs. I myself won't try a non-filtered DAC. My pre-amp and amp specs say that they can pass signals well past 100KHZ. I don't want to fry my tweeters with any nasty quantization noise.

 

[zheka]

very interesting. i could clearly hear the effect with my scott nixon chibi dac - the tone pitch starts getting lower past around 14khz. in fact even increasing pitch way beyond audible spectrum did not kill the sound. strange