CHANGSTAR: Audiophile Headphone Reviews and Early 90s Style BBS

  • December 31, 2015, 11:09:17 AM
  • Welcome, Guest
Please login or register.

Login with username, password and session length
Advanced search  
Pages: 1 2 3 4 [5] 6

Author Topic: Take a listen please  (Read 7215 times)

0 Members and 1 Guest are viewing this topic.

Tyll Hertsens

  • Gran' pappy of the hobby.
  • Pirate-at-Heart
  • Pirate
  • **
  • Brownie Points: +1099/-2
  • Offline Offline
  • Posts: 285
    • InnerFidelity
Re: Take a listen please
« Reply #40 on: June 25, 2013, 06:26:25 PM »

Appreciating the dialog here, thanks xnor.

I did have a quick listen to the files but didn't do any testing. I though they were such poor masters that they both sucked.

:)
Logged
Cheers,

Tyll (like on the floor only spelled different)

xnor

  • Pirate
  • **
  • Brownie Points: +39/-50
  • Offline Offline
  • Posts: 154
Re: Take a listen please
« Reply #41 on: June 25, 2013, 07:17:53 PM »

I've read the SACD is the same as the DVD-A so all I can think of is that you don't like the 5.1 to 2.0 downmix or you just dislike the recording itself. Will compare the downmix to the CD-layer version.

What version do you recommend, if any?
« Last Edit: June 25, 2013, 08:41:02 PM by xnor »
Logged
"I'm on a whole new adventure." - "Growing a mustache?"
"No. Bigger than that." - "A beard?!?"

Anaxilus.

  • Dikus Beligerantis Analmorticus
  • Pirate
  • **
  • Brownie Points: +65535/-65535
  • Offline Offline
  • Posts: 577
Re: Take a listen please
« Reply #42 on: June 25, 2013, 07:34:37 PM »

Appreciating the dialog here, thanks xnor.

I did have a quick listen to the files but didn't do any testing. I though they were such poor masters that they both sucked.

 :)


Personally I find that album overrated for mastering quality.  I never user it for testing.
Logged
If you do not change direction, you may end up where you are heading - Lao Tzu

Tyll Hertsens

  • Gran' pappy of the hobby.
  • Pirate-at-Heart
  • Pirate
  • **
  • Brownie Points: +1099/-2
  • Offline Offline
  • Posts: 285
    • InnerFidelity
Re: Take a listen please
« Reply #43 on: June 25, 2013, 08:30:43 PM »

Personally I find that album overrated for mastering quality.  I never user it for testing.

Exactly.  I do use "Walk Between the Raindrops" sometimes when I want to hear something with shitty compressed sound.

I like Donald Fagen a lot, but that album just pissed me off.
Logged
Cheers,

Tyll (like on the floor only spelled different)

Marvey

  • The Man For His Time And Place
  • Master
  • Pirate
  • *****
  • Brownie Points: +555/-33
  • Offline Offline
  • Posts: 6698
  • Captain Plankton and MOT: Eddie Current
Re: Take a listen please
« Reply #44 on: June 26, 2013, 02:39:33 AM »

You need an anti-aliasing filter. That's basically a steep low pass filter that removes (in practice: attenuates) frequencies above Nyquist.


Because ultra-high frequencies at the sampling rate, whether NOS or over-sampled or up-sampled, may destroy tweeters, cause amps to oscillate - they make the rest of the chain unnecessarily amplify and attempt to reproduce extra unneeded signals which the amps/tweeters may have never designed to do so. It's an engineering thing, which just as much about about margins and tolerances "the oh-shit factor" as making science tangible.


(This is why I feel Harold's O2 design with the pot between the voltage multiplier section and the current buffer is retarded - and why I've had to answer more than a few PMs here and over at HF on how to make the O2 work with even not so "hot" sources. I've even made the O2 clip myself with slightly less DAC voltage output that I thought would happen in theory. The assumption that the O2 would be always used with wimpy output DACs, or that end-users would possess sufficient technical knowledge about their DAC's voltage output, appropriate op-amp gain, etc. , is not one that would ever be made by a credible engineer meaning to offer the product to the public. At the very least, a warning label regarding DAC/source output and internal gain settings should have been silk-screened near the input jack.)


Some DAC chips produce more high-frequency junk than others. For example, I've used the output straight from AKM voltage-out DAC chips, but generally this is still not advised. I've heard of some folks rely on tubes (amps of output section of DACs) when not using a filter because of tubes' inherent bandwidth limitations to usually that of human hearing (when tubes are used for audio applications.)


The farther the ultra-high frequency junk is from 20kHz (~limit of human hearing), the better because more gentle, less steep filters (which have less phase shift and probably other more desirable behavior - this is ultrabike's area of expertise) can be used. The very early CD Players were NOS, and there was some audiophile debate back in the early 80s whether this harshness was because of the steep brickwall analog filters used to kill junk at 44.1kHz. Thus oversampling DAC were born. But please, let's not debate that. That was the 80s.
« Last Edit: June 26, 2013, 03:01:00 AM by purrin »
Logged

Helios

  • Guest
Re: Take a listen please
« Reply #45 on: June 26, 2013, 04:45:20 AM »

Anti-aliasing filters are used in ADCs, not DACs [correction by ultrabike: DACs can implement decimation filters which are a form of digital anti-aliasing].

An anti-aliasing filter is a steep lowpass filter which tries to eliminate frequencies above Nyquist, which is half the sample rate.
For instance, if you are converting an analog signal to digital at 48kHz, your ADC should have a lowpass that ideally rejects everything above 24kHz. This is because any frequency above the halfway mark (24kHz) could be falsely interpreted by the DAC stage as a corresponding lower frequency.

Look at image d in this figure:


The analog signal's frequency is 0.95 of the sample rate...in the case of 48kHz, we have a 45.6kHz sine wave. The black squares are the actual data points captured by the ADC stage. Now, when a DAC tries to reconstruct the sine wave, you can see that the data points form a nice super-imposed sine at 0.05 of the sample rate or 2.4kHz. There's just no way for the DAC to reconstruct anything above the Nyquist frequency, so we must get rid of those frequencies. You can imagine how nasty this could sound with actual music instead of sine waves. Ultrasonic harmonics/noise/garbage being interpreted as lower frequencies, mixed into the audible spectrum. Nasty.

These filters can't be theoretically perfect in practice because we're still dealing with the limitations of analog. The filter cannot be infinitely steep, as would be most ideal. The best ADCs/DACs typically are those with painstakingly-designed analog stages.

There are software tricks that can be done to reduce the complexity of the analog anti-aliasing filters (on the ADC side) and reconstruction filters (on the DAC side) required, BUT you still need great analog design to get quality results from digital...whether converting from analog or to analog. The design and quality of these analog filters is one big reason why DACs and ADCs can sound so different. It's not just ones and zeroes.
« Last Edit: June 26, 2013, 06:37:02 AM by Helios »
Logged

Solderdude

  • Grab the dScope Kowalski!
  • Able Bodied Sailor
  • Pirate
  • ***
  • Brownie Points: +206/-4
  • Offline Offline
  • Posts: 907
  • No can do skipper, the dScope was terminated
    • DIY-Audio-Heaven
Re: Take a listen please
« Reply #46 on: June 26, 2013, 05:19:00 AM »

Digital filtering at the recording stage is called anti-aliasing and is indeed meant to remove signals above half of the sample frequency as they can be 'mirrored' back in the audible range. In this case the sample clock is the mirror. All signals NEAR that sample frequency that are present in the original signal, that is to be recorded, thus have to be removed in an analog way.
The higher the sample frequency the higher the analog content may still be or the less 'steep' the filter can be.

As Purrin already mentioned, the steeper the filter the more post ringing (for analog) is present and the more phase and amplitude (ripple in the upper frequency range) problems exist.

In the Digital to Analog conversion part a filter is essential to create smooth transitions from one output voltage step to the other.
The posted diagram already shows the 'steps' get bigger the higher the signal frequency is.
Those 'errors' need to be removed.
This can be done by an analog (low pass) filter OR by upsampling (creating sample points between the actual samples) and calculating where they might have been through algorithms thereby reducing the output steps in size.
This way the amplitude of the 'steps' is made smaller and shifted to a higher frequency which is EASIER to filter with a NOT steep analog filter to remove the high frequency 'errors'.

So in the DAC a filter is needed to 'smooth' the analog output so the steps are not there anymore.
Both digital and analog ways exist to reach the same goal (an analog signal without 'steps') and both have advantages and disadvantages depending on the TYPE of filter used.

Both in the analog as well as in the digital realm different types of filters exist with different behaviour in the AUDIBLE band and outside of it.
Logged
Use your ears to enjoy music, not as an analyser.

ultrabike

  • Burritous Supremus (and Mexican Ewok)
  • Master
  • Pirate
  • *****
  • Brownie Points: +4226/-2
  • Offline Offline
  • Posts: 2384
  • I consider myself "normal"
Re: Take a listen please
« Reply #47 on: June 26, 2013, 06:15:34 AM »

Anti-aliasing filters are used in ADCs, not DACs.

Depends...

In the case of an up-sampling DAC, if the up-convert rate is an integer multiple of the original rate, then an anti-imaging (or interpolation) filter is used. However, if the up-convert rate is not an integer multiple of the original rate then down-conversion might be required as well. Down-conversion might imply a decimation filter, which is kind of a digital anti-aliasing filter...

---

On a different note, I find interesting that the ringing in the test track was applied in the same (roughly) region that my KSC75 and HD558 exhibit ringing... around 4 and 5 kHz... Maybe something like a modded HD800 with less nasties in that range will be more revealing in an ABX.
Logged

Helios

  • Guest
Re: Take a listen please
« Reply #48 on: June 26, 2013, 06:34:21 AM »

Digital filtering at the recording stage is called anti-aliasing and is indeed meant to remove signals above half of the sample frequency as they can be 'mirrored' back in the audible range. In this case the sample clock is the mirror. All signals NEAR that sample frequency that are present in the original signal, that is to be recorded, thus have to be removed in an analog way.
The higher the sample frequency the higher the analog content may still be or the less 'steep' the filter can be.

As Purrin already mentioned, the steeper the filter the more post ringing (for analog) is present and the more phase and amplitude (ripple in the upper frequency range) problems exist.

Good points. We can't have it both ways...speaking in terms of theoretical ideals in the time domain versus freq domain and vice versa.

In the Digital to Analog conversion part a filter is essential to create smooth transitions from one output voltage step to the other.
The posted diagram already shows the 'steps' get bigger the higher the signal frequency is.
Those 'errors' need to be removed.
This can be done by an analog (low pass) filter...

I thought a low-pass would only work in this application if the DAC could somehow generate a true impulse train (which is impossible in the real-world since the impulses are infinitely narrow).
So, if your DAC uses zero-order hold (sounds like what you're describing by "voltage steps"), then you need a filter that looks like this:

OR a multirate filter (downsampling, upsampling).

But a low-pass will not reconstruct the effects of zero-order hold. Am I wrong here?

Depends...

 a decimation filter, which is kind of a digital anti-aliasing filter...
Thanks for the correction.
Logged

ultrabike

  • Burritous Supremus (and Mexican Ewok)
  • Master
  • Pirate
  • *****
  • Brownie Points: +4226/-2
  • Offline Offline
  • Posts: 2384
  • I consider myself "normal"
Re: Take a listen please
« Reply #49 on: June 26, 2013, 06:59:36 AM »

I thought a low-pass would only work in this application if the DAC could somehow generate a true impulse train (which is impossible in the real-world since the impulses are infinitely narrow).
So, if your DAC uses zero-order hold (sounds like what you're describing by "voltage steps"), then you need a filter that looks like this:

OR a multirate filter (downsampling, upsampling).

But a low-pass will not reconstruct the effects of zero-order hold. Am I wrong here?

I think you are correct. Those are compensation filters which can be implemented in the digital domain...
---
So... Did you give the audio files comparo a shot?
popcorn
Logged
Pages: 1 2 3 4 [5] 6