Wyred4Sound DAC2 thd measured

VHF man · 06:58 AM

Here is fft analysis for 5.2kHz at 0, -10, -13 (dBfs)

SR = 48kHz, 24bits

Note the higher thd as the output level is increased. Level adjustment was via the dac's 32bit volume control. The load impedance was 20K ohms and a LM4562 preamp was used between the dac and the soundcard (Asus dx).

Note: the LF noise is due to a slight earth loop.

abraxalito · 10th February 2011, 06:42 AM

What's the vertical scale - 10dB per division?

VHF man · 10th February 2011, 06:50 AM

Quote:

Originally Posted by abraxalito

What's the vertical scale - 10dB per division?

Sorry, I should have mentioned it. Yes it's 10dB / div

Regards
vhf

qusp · 11th February 2011, 01:48 PM

some more information to accompany these measurements might render them useful to someone who doesnt own the AP. as it stands i'm not sure what to make of it. doesnt look too flash at all, but without something to gauge it by its not really that legible, to me

VHF man · 12th February 2011, 03:44 AM

Quote:

Originally Posted by qusp

some more information to accompany these measurements might render them useful to someone who doesnt own the AP. as it stands i'm not sure what to make of it. doesnt look too flash at all, but without something to gauge it by its not really that legible, to me

Sorry if the screen grab is a bit low-fi.

What I was trying to demonstrate here is that the 3rd harmonic makes an appearance near maximum output level. The thd looks to be up around 0.01% at 0dBfs but reduces to < 0.005% at -10dBfs and with only a 2nd order visible.

Whether you think that this level of distortion is significant is a matter of opinion - but ftr using the same test bed setup I can't see any distortion from my power amp (at any non clipping power level) and into 8 or 4 ohm loads.

analog_sa · 12th February 2011, 05:39 AM

Interesting. I wonder if it's possible to repeat the measurements at the output of the dac chip.

SY · 12th February 2011, 10:26 AM

Quote:

Originally Posted by analog_sa

Interesting. I wonder if it's possible to repeat the measurements at the output of the dac chip.

The issue is clearly analog distortion in the stages following the DAC. Not too severe, but it shouldn't be there.

janneman · 12th February 2011, 10:29 AM

Quote:

Originally Posted by SY

The issue is clearly analog distortion in the stages following the DAC. Not too severe, but it shouldn't be there.

For instance, how does the sound card do when connected output-to-input?

jan didden

VHF man · 12th February 2011, 02:03 PM

Quote:

Originally Posted by janneman

For instance, how does the sound card do when connected output-to-input?

jan didden

The input level to the sound card is the same for all 3 dac output level tests - as it appears on the analyser. I used a class preamp between the dac and the sound card to keep the sound card input level constant for the 3 measurements. Sure, the sound card and the preamp are contributing to the total distortion but the only parameter that's being varied in all 3 tests is the level at the dac output. FWIW the preamp + sound card thd contribution is difficult to measure - being so low.

jkeny · 12th February 2011, 03:02 PM

Interesting as I've seen the W4 being reported as being sibilant at times!

10th February 2011, 06:42 AM	#2
abraxalito diyAudio Member Join Date: Sep 2007 Location: Hangzhou - Marco Polo's 'most beautiful city'. 700yrs is a long time though... Blog Entries: 46	What's the vertical scale - 10dB per division? __________________ I think ideas are what you want to get rid of. I don't really like songs with ideas. - Leonard Cohen

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11th February 2011, 01:48 PM	#4
qusp Sometimes a square peg fits a round hole just fine diyAudio Member Join Date: Oct 2009 Location: Brisbane, Australia	some more information to accompany these measurements might render them useful to someone who doesnt own the AP. as it stands i'm not sure what to make of it. doesnt look too flash at all, but without something to gauge it by its not really that legible, to me

12th February 2011, 05:39 AM	#6
analog_sa diyAudio Member Join Date: Aug 2002 Location: Sofia	Interesting. I wonder if it's possible to repeat the measurements at the output of the dac chip.

12th February 2011, 03:02 PM	#10
jkeny Banned Join Date: Feb 2007 Location: Dublin	Interesting as I've seen the W4 being reported as being sibilant at times!

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