• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required as is 20 years of participation in forums (not all true). There are daily reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

Why DA/AD diff tests not getting the attention it deserves in measurements

Grooved

Addicted to Fun and Learning
Joined
Feb 26, 2021
Messages
509
Likes
308
My first guess might be a little more hum on unbalanced. With nulls of -89 db and lower it takes very little to worsen a null. As Paul said it should show up in FR or maybe phase (though I don't know why there would be a phase difference in balanced vs unbalanced).

So what are the differences if you null these two file captures against each other?
Here are the null results of both files, 1 is with Deltawave basic settings, and 2 with advanced settings enabled like bellow
advanced settings.PNG


Basic settings:
1.PNG

1'.PNG


Advanced settings:
2.PNG

2'.PNG
 

pkane

Major Contributor
Forum Donor
Joined
Aug 18, 2017
Messages
4,061
Likes
6,909
Location
North-East
Here are the null results of both files, 1 is with Deltawave basic settings, and 2 with advanced settings enabled like bellow
View attachment 232790

Basic settings:
View attachment 232791
View attachment 232792

Advanced settings:
View attachment 232793
View attachment 232794

Non-linear EQ is an advanced function, as I mentioned. It is sensitive to noise as it's performing a deconvolution of the original signal based on estimated impulse response. If the impulse response is noisy (the errors in spectrum/phase are random), deconvolution will not produce a good result. To help average out the noise, you may want to use smaller FFT size, for one. But, there's no guarantee that deconvolution will help in all cases -- it depends on the data, the original spectra, and the amount of noise. Check phase and spectrum differences with non-linear eq and without to see what effect it had on both.
 

Grooved

Addicted to Fun and Learning
Joined
Feb 26, 2021
Messages
509
Likes
308
Another thing I saw is that the main parts what gives lower difference results are when high frequencies are at higher levels.
We looked at DC, power supplies,... but not high frequencies.

This what happens at 1'43" in the "original" file (quickly captured from Foobar just to show): there was a jump (cymbals) just before, in grey in the picture
It also happens two other times later
main difference original and most of recordings.png


and just looking at two captures I made with 828MK2 and iD22 to check with another one, it's exactly where the difference has the worst result, for both devices and I think for most of all devices:

828MK2:
828MK2 - DW basic.PNG


iD22:
iD22 - DW basic.PNG


So are high frequencies the main problem?
 

Blumlein 88

Grand Contributor
Forum Donor
Joined
Feb 23, 2016
Messages
15,915
Likes
26,713
Another thing I saw is that the main parts what gives lower difference results are when high frequencies are at higher levels.
We looked at DC, power supplies,... but not high frequencies.

This what happens at 1'43" in the "original" file (quickly captured from Foobar just to show): there was a jump (cymbals) just before, in grey in the picture
It also happens two other times later
View attachment 232811

and just looking at two captures I made with 828MK2 and iD22 to check with another one, it's exactly where the difference has the worst result, for both devices and I think for most of all devices:

828MK2:
View attachment 232812

iD22:
View attachment 232813

So are high frequencies the main problem?
Could be, often differences in filter used cause differences in high frequencies. Especially with phase. If you don't use the advanced features, look at the phase and see if they diverge at the higher frequencies. Two devices could match very well, and even have nearly the same frequency response, but a phase response idfference can make the null less good. The advanced features of course compensate for that.
 

Grooved

Addicted to Fun and Learning
Joined
Feb 26, 2021
Messages
509
Likes
308
Could be, often differences in filter used cause differences in high frequencies. Especially with phase. If you don't use the advanced features, look at the phase and see if they diverge at the higher frequencies. Two devices could match very well, and even have nearly the same frequency response, but a phase response idfference can make the null less good. The advanced features of course compensate for that.
Thanks, I thought about the filter at first, and I will check phase.
 
Top Bottom