• 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!

Topping D90SE Measurements (DAC)

theREALdotnet

Active Member
Joined
Mar 11, 2022
Messages
262
Likes
313
So this stuff here, what’s causing it?

1649335214645.png


Is it to be expected from a 384kHz signal? Like I said, at -135dB and lower it’s not going to be a bother, but it does stick out in this plot.
 

bennetng

Major Contributor
Joined
Nov 15, 2017
Messages
1,457
Likes
1,396
Pardon my muddled terminology, if anything it would be aliasing, not anti-aliasing artifacts. But yes, from what I understand, aliasing is the result of intermodulation between the signal and the sampling frequency.
Aliasing is a digital term, which means analog conversion is not required to introduce aliasing. For example digital synthesizers and samplers can introduce aliasing artifacts even without analog conversion.

IMD on the other hand is an analog term, can happen with strictly analog equipment like tube amp and so on.
 

theREALdotnet

Active Member
Joined
Mar 11, 2022
Messages
262
Likes
313
IMD on the other hand is an analog term, can happen with strictly analog equipment like tube amp and so on.

Intermodulation can always occur when two signals are subjected to a non-linear transfer function, like being multiplied with each other or whatever. It doesn’t matter whether the signals are continuous or sampled.
 

theREALdotnet

Active Member
Joined
Mar 11, 2022
Messages
262
Likes
313
That's 100dB of clear range, below the signal (signal at -35dB)?

Yes, you’re right. I had assumed the signal peaked at 0dB (that Y axis is a bit hard to read).
 

bennetng

Major Contributor
Joined
Nov 15, 2017
Messages
1,457
Likes
1,396
From Monty, the presenter of the most frequently posted video on ASR, explained what is IMD:
Neither audio transducers nor power amplifiers are free of distortion, and distortion tends to increase rapidly at the lowest and highest frequencies. If the same transducer reproduces ultrasonics along with audible content, any nonlinearity will shift some of the ultrasonic content down into the audible range as an uncontrolled spray of intermodulation distortion products covering the entire audible spectrum. Nonlinearity in a power amplifier will produce the same effect. The effect is very slight, but listening tests have confirmed that both effects can be audible.

intermod.png


Above: Illustration of distortion products resulting from intermodulation of a 30kHz and a 33kHz tone in a theoretical amplifier with a nonvarying total harmonic distortion (THD) of about .09%. Distortion products appear throughout the spectrum, including at frequencies lower than either tone.

Inaudible ultrasonics contribute to intermodulation distortion in the audible range (light blue area). Systems not designed to reproduce ultrasonics typically have much higher levels of distortion above 20kHz, further contributing to intermodulation. Widening a design's frequency range to account for ultrasonics requires compromises that decrease noise and distortion performance within the audible spectrum. Either way, unneccessary reproduction of ultrasonic content diminishes performance.
 

Music1969

Major Contributor
Joined
Feb 19, 2018
Messages
2,853
Likes
1,554
Yes, you’re right. I had assumed the signal peaked at 0dB (that Y axis is a bit hard to read).
So it's not really that great compared to some other DACs.

But may improve with updated firmware that fixes this MQA crap.
 

theREALdotnet

Active Member
Joined
Mar 11, 2022
Messages
262
Likes
313
From Monty, the presenter of the most frequently posted video on ASR, explained what is IMD:

Yes, I’ve read it. It kind of poses more questions than it answers, though, for example:
Either way, unneccessary reproduction of ultrasonic content diminishes performance.

Given that audible vs ultrasonic is an arbitrary distinction as far as signal processing is concerned, doesn’t this mean we would gain higher performance if we limited the bandwidth of ADCs and DACs even further to, say, 18kHz?
 

srkbear

Addicted to Fun and Learning
Forum Donor
Joined
Nov 16, 2021
Messages
508
Likes
637
Location
Dallas, TX
But yes, they do sometimes release firmware updates:
I’ve been to that site innumerable times—they release updated drivers, but actual firmware upgrades almost never, if at all. It’s my only criticism of Topping, that they don’t respond to consumer feedback and refresh their gear, and the other salient Chinese manufacturers behave similarly. Fortunately I’m happy with my D90se, but I’d prefer that they revisit their work every so often.
 

Sonic-Wall

Member
Joined
Mar 29, 2021
Messages
17
Likes
9
@srkbear
Maybe you should replace your Topping with a RME ADI-2.
They provide firmware updates on a regular base with lot‘s of enhancements.
 

srkbear

Addicted to Fun and Learning
Forum Donor
Joined
Nov 16, 2021
Messages
508
Likes
637
Location
Dallas, TX
Just tried to help you saving your precious time and enjoy your music;-)
I’ve considered the RME innumerable times. It’s a great unit! Love the DSP features. If I didn’t already have a dedicated amp (the iFi Pro iCAN Signature) with it’s own analog bass enhancements and the DSP functions of Roon, I’d go for it—and although I try to remain closeted about it, I have a lot of very good masters in MQA format that I’d miss with the RME. Perhaps when I decide to outfit another room in my house with audio, I’ll reconsider. Peace!
 
Top Bottom