Topic: Metrum Acoustics Quad Measurements (NOS Mini DAC) (Read 12357 times)

ultrabike · « **Reply #20 on:** December 07, 2013, 10:47:03 AM »

LOLs!!! Actually I've seen that Kusunoki paper being thrown around at some other forums I think, and it usually goes over people's heads, understandably so. I had to stare at it for some time.

Anyhow, I also think cans tend to be the limiting factor on most rigs anyway. Ha! IMO changing the sampling rate, which will change the LPF effect of the S/H has some cool factor to it. The slight roll-off would be welcome on some cans...

karma points!

Hands · « **Reply #21 on:** December 07, 2013, 11:03:26 AM »

Yes, I saw that paper before as well. I read more summaries about it than the paper itself, I think, ha.

I find myself wanting to EQ treble all the time, so the roll-off is really a big plus for my ears. Sometimes I think I should just buy an LCD-2 or HD650 and be done with it, LOL.

Hands · « **Reply #22 on:** December 07, 2013, 03:42:07 PM »

I'll be attaching some ARTA measurements in my next few posts. Let me know if you have any questions about my methodologies, notice any flaws that need corrected, want to offer other test ideas for me to run, etc.

I also can't necessarily say everything was measured correctly (did my best) or that I necessarily understand what all of these measurements mean or if they hold any value.

1. Periodic Noise Impulse Response 24/96
2. MLS Impulse Response 24/96
3. Sine Sweep Impulse Response 24/96
4. Frequency Response and Distortion generated by above sine sweep impulse 24/96
5. FR, Phase, and Cohesion (no idea if this is right, also no idea what cohesion is...this is a linear average using PN Pink Noise)

Yep, it's a NOS DAC.

Hands · « **Reply #23 on:** December 07, 2013, 03:47:06 PM »

These are not all to same scale necessarily. Manually zoomed in to get a better picture.

1. 1KHz Sine Wave - 16/48
2. 1KHz Sine Wave - 24/96
3. 10KHz Sine Wave - 16/48
4. 10KHz Sine Wave - 24/96
5. 20KHz Sine Wave - 16/48
6. 20KHz Sine Wave - 24/96
7. 20KHz Sine Wave - DAC set to 16/176.4, A/DC set to 24/96, and ARTA set to 16-bit, sine wave sampled at 192KHz

That last result is particularly interesting. These show how the NOS DAC's sine wave response improves at higher frequencies with a higher sampling rate.

Hands · « **Reply #24 on:** December 07, 2013, 03:49:47 PM »

1. 25Hz Square Wave 24/96
2. Zoomed-in view of the above. No idea if this has any value or means anything or not, but did notice the rough texture. Higher frequency sine waves would not allow me to zoom in as closely.
3. 25Hz Square Wave 24/96
4. 1KHz Square Wave 24/96

There is a good chance I did not set the square wave tests up optimally.

Hands · « **Reply #25 on:** December 07, 2013, 03:53:57 PM »

Do note FFT size and also compare with RightMark results. Software was set to 0dB but sometimes reports lower. I can't verify there aren't artifacts in here or not! When listening to music, I set the JKSPDIF to 0 no matter what. I don't think this makes a difference if using WASAPI or Kernel Streaming. But when doing these measurement tests, it was very hard finding the right balance of volume on the DAC/JKSPDIF and A/DC. When adjusting the levels on RightMark, I couldn't set the JKSPDIF and DAC to 0 like normal and had to balance that volume setting with the SB1240. While you could get the levels to match on a few different mixture of settings, some would introduce more distortion than others. I tried to narrow it down to produce the best, most consistent results possible. As such, assume these might contain artifacts due to a less-than-optimal measurement setup, but they should still hold good information and value regardless.

1. 1KHz Sine Spectrum - 0dB - Linear Avg - 24/96
2. 100Hz Sine Spectrum - 0dB - Linear Avg - 24/96
3. 60Hz and 7KHz Dual Sine Spectrum (4:1 ratio) - 0dB - Linear Avg - 24/96
4. 25Hz and 66Hz Dual Sine Spectrum (1:1 ratio) - 0dB - Linear Avg - 24/96
5. Noise - Linear Avg - 24/96
6. Noise - Peak Avg - 24/96

xnor · « **Reply #26 on:** December 07, 2013, 04:51:02 PM »

The irony is, if you associate old D/A converter performance with "digital sound" or "digitis", then non-oversampling DACs will give you exactly that.

Look at this:

The green dots are the samples. The blue sine is the input and output when correctly reconstructed.
Purple shows how non-oversampling DACs do it. Red is linear interpolation. Some audio editors display waveforms incorrectly that way.

@ #22: Notice how all the impulse responses look very different. It shouldn't make much difference if you use noise, MLS or a sweep to generate the impulse response but since a non-oversampling DAC just holds the last sample value.... And this is with the impulse response of course excluding any nonlinearities.

Solderdude · « **Reply #27 on:** December 07, 2013, 05:45:50 PM »

Play with the 'Wnd' settings box (Arta) that now says 'Hanning' and you will get sharper defined spectrum plots.

Also note that the steps that are (most likely) there in the output of the NOS DAC will be 'ironed' out a little by 'brickwall' filter in the ADC of the SB1240 card as well so may well be more severe in real life than when measured.
A real oscilloscope is the only instrument that can really tell.
The pulse edges are probably a lot 'steeper' than the SB1240 can show.

What does a pulse look like when played through the XXHE upsampling algorithm ?

xnor · « **Reply #28 on:** December 07, 2013, 07:08:19 PM »

Adding to my previous comment about the looks of an impulse: a CD is not going to contain a perfect impulse. Even if some instrument came close (which is pretty much impossible, but let's say it does) it would still be bandlimited and probably not hit the sampling interval at exactly the center:

(This is with 160 kHz low pass filter, hence the blips)
The funny thing is that if the impulse had happened a tiny bit earlier or later, the non-oversampled result would look completely different (again, since it doesn't respect the sampling theorem).

The "perfect impulse" these people are talking about is simply a marketing ploy.

Hands · « **Reply #29 on:** December 08, 2013, 12:48:27 PM »

Marketing ploy? In audio? I've never heard of such shenanigans!

Thanks, guys. You bring up good points and, as always, I appreciate the information and discussion!

Solderdude, I'll play around with ARTA more...probably sometime in the next few days. I'll have to figure out how to record an impulse response from XXHE (I'm assuming I can do this in ARTA?). Any other suggestions for things to test, especially to test XXHE's filtering/upsampling?

If I were to start measuring more gear seriously, I'd invest in an oscilloscope (and a better A/DC with wider options). Doing what I can for now based on my relatively limited hardware and knowledge, but it is fun!

It's clear that NOS DACs have a host of inherent issues that can easily be demonstrated by simple measurements and analysis, and I do appreciate the hard, technical details everyone has shared. Solderdude touched on this as I've mentioned, but is there anything that can be said about how it all translates into what we hear during music playback? Are the technical downsides really all that unpleasant, or is it hard for humans to really notice (assuming downsides are of similar magnitude to these measurements)? To what extent can software playback and upsampling methods improve on this?

There is gear, after all, that measures poorly in the grand scheme of things but receives widespread praise even from the types of folks that participate in this forum. The Vali is a good example, though I understand it's not a DAC and can't be compared in the same ways we're discussing, but it does tie into my point and my questions. A counterpoint could be made for the ODAC/O2...measures great, but I get the sense that most people here don't think it's the end-all-be-all.

Also, what listening experience do you guys have with NOS DACs? What experience with NOS DACs and various software playback and upsampling methods? I am not very experienced with DACs and, as such, really value the subjective impressions from the experienced members on the site, so this is an honest question. Hoping others can chime in...

Author Topic: Metrum Acoustics Quad Measurements (NOS Mini DAC) (Read 12357 times)

ultrabike

Re: Metrum Acoustics Quad Measurements (NOS Mini DAC)

Hands

Re: Metrum Acoustics Quad Measurements (NOS Mini DAC)

Hands

Metrum Acoustics Quad DAC - ARTA Impulse Response, FR, Phase Tests

Hands

Metrum Acoustics Quad DAC Sine Wave Response - ARTA

Hands

Metrum Acoustics Quad DAC - Further Sine, Square wave testing in ARTA

Hands

Metrum Acoustics Quad DAC - ARTA Spectrum Tests

xnor

Re: Metrum Acoustics Quad Measurements (NOS Mini DAC) - UPDATED 12/7 w/ new tests

Solderdude

Re: Metrum Acoustics Quad Measurements (NOS Mini DAC) - UPDATED 12/7 w/ new tests

xnor

Re: Metrum Acoustics Quad Measurements (NOS Mini DAC) - UPDATED 12/7 w/ new tests

Hands

Re: Metrum Acoustics Quad Measurements (NOS Mini DAC) - UPDATED 12/7 w/ new tests

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Author Topic: Metrum Acoustics Quad Measurements (NOS Mini DAC) (Read 12357 times)