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Old 2nd April 2012, 02:36 AM   #131
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Yep, I am stupid, can you move on?
You, as a illuminated teacher, care to explain how that non-filtered garbage shown in the previous picture can sound good?
We have alias products all the way to -32dB. And this is only from two fundamentals. That's the evidence that you missed - was there since 1982 when they invented the CD format.
Let me put the pic one more time so you don't miss it:
Click the image to open in full size.

Last edited by SoNic_real_one; 2nd April 2012 at 02:43 AM.
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Old 2nd April 2012, 02:46 AM   #132
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Originally Posted by SoNic_real_one View Post
You, as a illuminated teacher, care to explain how that non-filtered garbage shown in the previous picture can sound good?
Looks to me to be test tones. Who listens to test tones and declares they 'sound good' please?
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Old 2nd April 2012, 03:12 AM   #133
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ahhh that old chestnut.....
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Old 2nd April 2012, 03:14 AM   #134
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Originally Posted by Ken Newton View Post
I've always wondered about the notion of aliasing in the DAC reconstruction filter.
I've seen it myself in action. It was when I playing around with a SAA7321 'Bitstream' DAC - which has an internal 4X FIR filter (similar to the SAA7220 in characteristics) prior to more serious oversampling by other means. The aliasing at 20kHz gave rise to a AP measured THD of 1% or so. This of course wasn't harmonic distortion, but the 24k1 alias product.

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My theory as to why redbook CD has traditionally dissapointed many audiophiles follows, taken from my recent posting on the subject in an AudioAsylum thread:
An interesting read My own hypotheses are somewhat different, focussing more on implementation (engineering) details rather than the theory.

Firstly as Dan Lavry points out (and Bruno hints at), DACs perform worse at higher sample rates. NOS gives the DAC the best shot at performing - lowest glitch density.

Second, digital filters in OS chips are almost always half-band, giving rise to the listening effects you noticed. Hence apodizing filters are part of the solution to listener fatigue, as you note.

Thirdly many DAC's analog stages suck in practice (sound quality wise). The manufacturers suggest using audio opamps for what's a video signal. Intermodulation abounds although it doesn't show up on traditional measurements. NOS DACs have simpler, or no, analog stages able to introduce such nasties. OS DACs present greater challenges to analog stages because of the sample rate multiplication.

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Mike Story of dCS has published a paper concluding that to be one of the reasons why high sample rate digital sounds superior to CD.
I have a question - if Mr Story is the expert on what sounds good, why does his company's own DAC fail to persuade Martin Colloms by such a huge margin compared to Metrum? The price difference is huge. Is it purely down to personal taste or is there something more universal we can learn here?

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One of my self designed experimental DACs contains a programmable digital SINC filter. This programmable filter has enabled me to empirically evaluate oversampling, non-oversampling, and apodising digital filters. Here's what I heard. As is well known by now, non-oversampling, aka, NOS - which eliminates the playback SINC filter but does not affect the recording and mixing SINC filters - produces the natural and non-fatigueing sound so typically lacking in CD. Apodising - which retains the playback SINC filter, but removes the affect of the recording and mixing SINC filters - sounds equally natural and non-fatiguing as NOS. Oversampling - with all SINC filter responses in place - on the other hand, produces the typically fatiguing and course CD sound.
Is the apodizing filter you're listening to also oversampling? Or does it just implement an aggressive low-pass but keep the sample rate at 44k1?
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Old 2nd April 2012, 06:00 AM   #135
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Quote:
Originally Posted by SoNic_real_one View Post
Yep, I am stupid, can you move on?
You, as a illuminated teacher, care to explain how that non-filtered garbage shown in the previous picture can sound good?
We have alias products all the way to -32dB. And this is only from two fundamentals. That's the evidence that you missed - was there since 1982 when they invented the CD format.
Let me put the pic one more time so you don't miss it:
Click the image to open in full size.
Nice pic, and here's the one from the Hifi Critic interview (I assummed it's the same as your's with the 19/20 kHz testtones). I'm sure if I were to use the AP we have at work, I'd come up with the same results.

Thanks to a test CD with tones up to 20 kHz that I've owned since I could still hear 20 kHz, I now know that 18 and 20 kHz are totally gone, and 16 kHz needs a higher setting of the volume knob.

Lay may hearing threshold over this graph (and lets not forget masking), and there you have the explanation why I don't hear any artefacts. The perfect low pass filter at work.

I'd like to add that when I was younger, in the early years of lossy compression (PASC and ATRAC), I could easily tell without AB comparison if I was listening to PASC/ATRAC processed music because of chirpy tones in the mid and treble, especially in "complex" passages like the audience clapping, or recordings with a lot of tape hiss. Not unlike lower MP3 bitrates (128 kbps), but somewhat different.
I'm willing to accept that this DAC wouldn't have been my choice back in those days...
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Old 2nd April 2012, 07:28 AM   #136
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Originally Posted by SoNic_real_one View Post
Can I see a pic of your dCS Scarlatti?
LOL.

You can't get over the fact, that the DAC sounds excellent, do you ?
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Old 2nd April 2012, 08:31 AM   #137
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May I suggest a few members to start a thread on OS vs NOS, and not pollute this thread any further?
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Old 2nd April 2012, 01:28 PM   #138
tvi is offline tvi  Australia
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A little bit of sleuthing and it seems to me to be a DAC8581, the 4 ground pins are a giveaway, anybody with this dac and a multimeter should be provide confirmation?

Best pic I could find, just cropped and enlarged

Now to hunt down some Sasquatches
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Old 2nd April 2012, 01:30 PM   #139
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Originally Posted by Elberoth View Post
LOL.
You can't get over the fact, that the DAC sounds excellent, do you ?
So you are just another poser...

Quote:
Originally Posted by tvi View Post
A little bit of sleuthing and it seems to me to be a DAC8581, the 4 ground pins are a giveaway, anybody with this dac and a multimeter should be provide confirmation?
Also see the DAC8580, a member of the same family. The DAC8580 combines DAC8581 with an on-chip, 16x over-sampling digital filter.

Last edited by SoNic_real_one; 2nd April 2012 at 01:34 PM.
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Old 2nd April 2012, 01:38 PM   #140
tvi is offline tvi  Australia
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DAC8580s pinout doesn't match though
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