Review and Measurements of Intona USB Isolator for Audio DACs

[Jimster480]

I had a HP laptop that used a 3-prong power plug which would produce a nasty HF buzz when used with grounded amps at the end of the chain, but no buzz with ungrounded amps. Fits a ground loop pattern, no?

I had a laptop also many years ago that would cause a buzz in my headphones when its plugged in. I had it happen to my HTC M8 also, and I had the phone replaced.

 

[gvl]

I had a laptop also many years ago that would cause a buzz in my headphones when its plugged in. I had it happen to my HTC M8 also, and I had the phone replaced.

I was just trying to provide a counter-example to the statement that ground loop is always low-frequency hum. I'm sure many of us heard their audio gear buzzing, but not all cases can be linked to ground loops.

 

[amirm]

Even if we look at the statistics of HDtracks.com, the prevailing format of all new rock / pop HD-albums will be 24 bit / 44.1 kHz not 24/96 or 192 kHz.

The 24-bit/44.1 kHz stuff is really CD masters without the final dither and conversion to 16. Vast majority of high-res content that I have downloaded from there and elsewhere is 96 kHz or 192. Here are the stats in my Roon library:

As you see I have over 230 albums at 96/192.

 

[amirm]

I suggest to establish measurements with TWO reference sampling frequencies. At least, we can detect the weak resampling inside DAC's.

I should say that in the few times I have done this, there was not much to distinguish between the two. Still, I will test both in a future review to see if there is enough difference to make it worthwhile to double the workload there.

 

[dir]

Thank you for quick response, Amirm! You're doing the right job.
I also prefer 192 for my vinyl rips, but objectively speaking, today the music industry uses this frequency only for a flat transfer from old analog master tapes.
In fact, the vast majority of multisessions in record studios are made in 24/44 ( or 24/48 for TV broadcasters). They believe that this is enough. I would also think so, if it were not for the barbarous application of limiters, exciters and other gear for dynamic compression. It crushes music even mixed in 24/96. It makes dynamic range flat, but this is not the end of story. Nobody cares about the tremendous amount of inter-sample distortions at the DAC when it receives a signal with a full scale of 0dBFS .

 

[Blumlein 88]

Thank you for quick response, Amirm! You're doing the right job.
I also prefer 192 for my vinyl rips, but objectively speaking, today the music industry uses this frequency only for a flat transfer from old analog master tapes.
In fact, the vast majority of multisessions in record studios are made in 24/44 ( or 24/48 for TV broadcasters). They believe that this is enough. I would also think so, if it were not for the barbarous application of limiters, exciters and other gear for dynamic compression. It crushes music even mixed in 24/96. It makes dynamic range flat, but this is not the end of story. Nobody cares about the tremendous amount of inter-sample distortions at the DAC when it receives a signal with a full scale of 0dBFS .

https://benchmarkmedia.com/blogs/ap...il&utm_term=0_7c8c792ee5-b679e01ca0-198220265

Benchmark does. I do think they have overblown the issue though it can happen.

We also have discussed the effect some here in at least a couple threads. Here is one:

https://audiosciencereview.com/foru...ise-clipping-and-upsampling-dac-effects.1835/

 

[DonH56]

I had a HP laptop that used a 3-prong power plug which would produce a nasty HF buzz when used with grounded amps at the end of the chain, but no buzz with ungrounded amps. Fits a ground loop pattern, no?

Yes. That is what mine does. The ground noise tends to be more wideband and obnoxious on many computers.

 

[Jinjuku]

I guess a less noisy, but not quiet, USB is the reason for discussions on differences between streamers.

Nope. It's the DAC's themselves that are to blame.

 

[Arnold Krueger]

I had a HP laptop that used a 3-prong power plug which would produce a nasty HF buzz when used with grounded amps at the end of the chain, but no buzz with ungrounded amps. Fits a ground loop pattern, no?

Not necessarily. It could also be a ground potential difference problem. Besides, I said "Ground loops are almost universally characterized by being a low frequency hum..." knwing full well that with grounding problems there are no absolutely universal rules.

 

[Palladium]

Amir is obviously a fraudster.

He didn't perform the test exactly at 150AU from the barycenter of the Solar System outside the heliopause and exactly at 20th October 2020 @ 0420 hrs, which is why he didn't measure anything significant.

 

[Arnold Krueger]

thank you for investigation.
my question about sample rate of J-test.
why 48 kHz not 44.1 kHz? it would be interesting to evaluate the character of jitter in the same mode as music content.

Probably one of complete and up-todate papers about the J-test Jitter is by Julian Dunn and was published by Audio Precision: A copy of it is here: https://pdfs.semanticscholar.org/5763/8ec2b495f3c3e7f41deba07a966c9fc92db6.pdf .

Quoting from it:

"
Sampling Jitter / Data Jitter Susceptibility.

J-test is an AES3 test signal that was developed to maximize the coherence of data patterns while at the same time providing a basic high-level stimulus tone. This test stimulates worst-case levels of data-jitter.

The signal has two components, the first being an un-dithered square wave with a period of 4 samples. A cycle of this is shown here in hexadecimal notation: C00000 (-0.5) C00000 (-0.5) 400000 (+0.5) 400000 (+0.5) On conversion to analog at a sample rate of 48 kHz this signal would produce a sine wave with an amplitude of –3.01 dB FS at 12 kHz. (It looks like a square wave with a peak amplitude of –6.01 dB FS but in a properly band-limited system this sequence of values represents a sine wave of amplitude –3.01 dB FS.) This is added to the second component, an undithered 24-bit square wave of amplitude 1 LSB, made by switching between the following: 000000 (0) FFFFFF (-1 LSB) This square wave is repeated at a low frequency. The frequency is not critical but, for a sample frequency of 48 kHz, a rate of 250 Hz is normally used, as that makes the signal synchronous with the AES3 channel status block of 192 samples.
"

Beyond a certain point in time we hear no more from Dunn about the J-Test as unfortunately he had an early passing January 23rd, 2003.

Thus the J-Test is defined by its author as a specific sequence of particular samples, repeated as required with considerable latitude granted for the chosen pattern of repetition.

The sample rate of the data can vary but the proper sequence of samples is a proper J-Test as long as the defined sequence of samples is repeated.

 

[dir]

I believe this research will also be interesting https://service.tcgroup.tc/media/Level_paper_AES109(1).pdf

 

[RayDunzl]

I believe this research will also be interesting https://service.tcgroup.tc/media/Level_paper_AES109(1).pdf

I'd insert a frowny face here but I loathe using emoticons.

 

[chungjun]

I have an iFi iUSB3.0 in my chain... I admit, often, I wonder if it does anything (and my ears doesn't seems to tell me much). "Better with than without" I keep telling myself and without the technical know-how (not giving an excuse, stating facts) I cannot objectively conclude.

Reading this post, correct me if I'm wrong, I am of the view that even if these devices do anything, they probably aren't doing much.

 

[dir]

I'd insert a frowny face here but I loathe using emoticons

whats the point of your claims?
well, maybe your avatar is frowny enough but it was published in the same year as Dunn's works
I suppose since that times the measurement procedures and the behavior of the converters on the 0 dBFS are not changed

 

[Final]

I have an iFi iUSB3.0 in my chain... I admit, often, I wonder if it does anything (and my ears doesn't seems to tell me much). "Better with than without" I keep telling myself and without the technical know-how (not giving an excuse, stating facts) I cannot objectively conclude.

Reading this post, correct me if I'm wrong, I am of the view that even if these devices do anything, they probably aren't doing much.

I have an Ifi iUSB3.0 myself. Would have liked to see it measured. It seemed subjectively to do some good when coupled in a noise ridden system, but is it placebo or not? I guess we get the answer if it lands on the test bench in the future.

 

[Soniclife]

I have an Ifi iUSB3.0 myself. Would have liked to see it measured. It seemed subjectively to do some good when coupled in a noise ridden system, but is it placebo or not? I guess we get the answer if it lands on the test bench in the future.

I have a low-tech way of testing this sort of thing, and to see if you need the fix in the first place.
The measurements don't show any change to jitter, only to noise making through the DAC, so sound quality changes should be limited to changes in noise, so why not simply turn up the volume and see what you can hear. Unfortunately most DACs have some form of mute when not being sent a signal, so this will often need to be done with a very quiet music signal to stop the mute activating, I do this by making a quiet track much quieter using audacity, then play it back with a digital vol control turned way down in the software player, and the amp turned way up. In my system I get silence on optical and ethernet inputs with this test, but small amounts of noise make it through USB. Obviously take care to protect your system and hearing if doing this.

 

[amirm]

Reading this post, correct me if I'm wrong, I am of the view that even if these devices do anything, they probably aren't doing much.

Odds are that your conclusion is correct based on a number of these devices which I have tested. But I am happy to measure it if any of you want to loan it to me. At $399, I am not inclined to buy it myself.

 

[RayDunzl]

whats the point of your claims?

Did I make a claim?

I see a paper published 18 years ago, and, at least from the ResearchGate repository, two "reads". My brain juxtaposed that with your adjective "interesting" in reference to the paper. That's what prompted the near insertion of a frowny-face emoticon.

well, maybe your avatar is frowny enough but it was published in the same year as Dunn's works

My personal interpretation of my avatar, is that it exhibits a slight sneer, not a frown. It's my universal substitute emoticon, attached to all my dreary posts here.

I suppose since that times the measurement procedures and the behavior of the converters on the 0 dBFS are not changed

Maybe measurement has not changed. However, the maker of my DAC surely read the paper, and the behavior on my converter is claimed to take intersample-overs into account, to avoid the problem they cause in converters without appropriate headroom.

https://benchmarkmedia.com/blogs/application_notes/intersample-overs-in-cd-recordings

 

[dir]

, at least from the ResearchGate repository, two "reads"

When i find something interesting, i don't really care about indexing machine score. its like try to evaluate music from top charts))
Most of people even doesn't knew what a "DAC" or "Hi-Res", who cares?

the maker of my DAC surely read the paper, and the behavior on my converter is claimed to take intersample-overs into account, to avoid the problem they cause in converters without appropriate headroom.

You can be proud by your DAC, but these problem are still alive. I was check lots of modern hi-fi devices. Even professional machines suffered from intersample peaks and clipping on 0 dbfs.