|BTW: Here's the "Flasher Gremlin" for sale if you're a model collector...|
Hmmm... At least that's the kind of interpretation one might be tempted to consider after reading this "truthy scientific" article on AudioStream ("USB Audio Gremlins Exposed: Beyond 1s and 0s, by iFi Audio")! What can I say? Brutal! Nice example of content from Industry to instill some measure of concern among susceptible audiophiles.
Okay, let me first say that I'm not claiming that USB is perfect - nothing is... You could run into issues. But the fact really is that these days, with a decent asynchronous DAC (what decent audiophile USB DAC these days isn't asynchronous?), one should not be concerned with data errors, jitter issues, and I have yet to come across noise pollution from a computer other than atypical situations like what I demonstrated a year back.
A typical $10 USB cable made to appropriate specifications by a reputable brand is fine.
With that said, let's delve into this short "article" and consider truth and fiction (delusion?)...
Based on the concept of "fair use", I will quote this article and add comments in context for the sake of debate and critique.
[April 15, 2016 EDIT: I guess iFi was unhappy with me quoting the article... Fine. I'll just remove the majority of the quoted text but leave the first and last few words to indicate the quote being referred to... Go visit the AudioStream site for the full text. I suggest to just open two windows side-by-side and match up the original article text with the comments. I trust this would not be a problem.]
1. Bits are really ...
... limitations and problems.
Guys. Please show us where and how "bits are bits" is actually "debunked" and by what amount does this affect the actual perceptible sound quality with a modern digital audio device. Dragging out a Stereophile article from 1996 using jitter simulations in the multi-nanosecond range which is known to cause data integrity errors (100+ns it seems!) when any reputable DAC interface has jitter measured in picoseconds (one thousandth of a nanosecond) is rather disingenuous and adds to the FUD. As someone who wears eyeglasses, it's like claiming that there's no way any person with myopia would ever be able to achieve 20/20 vision and that's cause for concern because someone in 1350 wrote an article claiming that even the best tradesmen are unable to shape the convexity of the glass to an accurate diopter. That's absurd!
Yes, jitter varies between different interfaces but as I have shown previously, this is a function of the DAC/computer interface. No evidence at all that USB cables change the sonic output. Also, no evidence at all that OS tweaks or different machines make any difference with an asynchronous USB DAC. Who's delusional?
Please, do reveal these "reliably measurable differences".
1.2 Asynchronous USB audio ...
... that SPDIF implementations needed care.Indeed asynchronous USB interfaces improve the ability to provide accurate timing data to DACs as I demonstrated a few years back and can be summarized in the following 16-bit J-Test FFTs:
|Old AUNE X1 v.1 DAC playing the 16-bit J-Test using adaptive isochronous USB 1.0 interface vs. same J-Test with asynchronous USB 2.0 CM6631A interface (through a small length of coaxial S/PDIF).|
1.3 What about alternative systems...
... there is no silver bullet/panaceaOkay, let's talk ethernet... Is this interface not extremely reliable for data-free transmission? (You better believe this since the whole of the Internet depends on this fact especially if you make financial transactions!) Is ethernet not asynchronous, buffered, and streaming devices using ethernet tend to be very jitter-free? So what if the interface is so powerful that it can handle "general purpose systems"? Folks, if a gigabit home network is capable of transmitting 4K video without a hitch, what's the big deal with hi-res audio which uses even less bandwidth? As I have shown previously, ethernet works well and can transmit over long distances.
2. A Matter of ...
2.1 Audio vs. Data ...
... ‘Bulk/Burst mode’ transfers.
Yeah. So what? Sometimes there's more data to send, other times there's less. Even at stereo 32/768, we're looking at <50Mbps transfer speed. USB 2.0 is capable of 480Mbps ideal top speed (and it can usually achieve at least 350Mbps in the real world with hard drives I've used). Please elaborate on what the concern is here... And BTW, why is anyone even throwing out 32/768 other than trying to impress with big numbers. Seriously, what educated and reasonable human being believes 32/768 is even a desired PCM format for consumer consumption!?
2.2 What is Isochronous...Again, so what? Some transfers are isochronous and some drivers use bulk transfers. Just how error-prone do these guys think a decent typical USB cable is for us to fear the lack of CRC error checking and retransmission? Care to demonstrate what a mild case of "signal distortion" sounds like? As for "worst case" clicks and dropouts, how common is that with a decent DAC and standard laptop that's fit to handle basic decompression tasks (eg. MP3, AAC, FLAC) in 2016? (BTW, for those curious, here's what a bad USB cable "sounds" like and the type of distortion one hears due to data error - it ain't pretty.)
... still uses Isochronous mode to transfer audio.
3. Of Mice and Fans...
... not work with the same port or cable.Isn't it a little useless to be so vague?! Please give us an example of what computer, DAC, and cable which is up to basic specifications but suffers from audio subsystem failure yet both low speed (mouse, printer) and high speed (hard drives, flash drives) devices function without signs of an issue. Surely this would be practically helpful for everyone to learn to avoid this hardware combination.
3.2 Which way did USB audio...
... and a low sample rate.Yeah, sure. Don't buy out-of-spec cables and ports then. The same can be said of out-of-spec SPDIF cables, low quality CAT-5e cables, cheap Firewire ports/cables, etc... But are in-spec cables and ports that hard to find or expensive? I think not. Funny the adjective "catastrophic" being used in this context of what we're discussing?! So scary.
3.3 Encountering unexpected Cyclic Redundancy...
... audio improvement devices and cables.Where did 'fmak' make these testimonial claims about CRC errors? I presume it must be on the Audio Asylum somewhere? Is this where manufacturers get their research data; from the "inmates"!? Why is his post/claim not included in the References section below? But seriously, we're looking typically at less than 10' of cable. Surely active USB cables are not necessary!
4. Ports, Cables, Packets...
4.1 Being ‘PC’
... technical performance of different USB ports:
... port is 'good' and the other 'bad'."Okay, sure. Again, some hardware might be faulty or out-of-spec but that can be said of any device out there. And yes, of course you don't put poorly shielded cables where they can pick up interference. Again, just how common are all these "possible source(s) of USB signal distortion"? IMO it's not common at all with decent equipment and a reasonable length of USB cable.
4.2 USB cables
... USB 2.0 use and follow the formal USB specifications closely.Yup. Fine. Drag out the ol' eye-diagram again huh? (Some measurements came out years ago around this.) Look, so long as the eye diagram is within tolerance, we won't have any data error. What's more important is to demonstrate examples of anomalies that can result in analogue output issues from the DAC; this is something I have never seen from the magazines or from these manufacturers. After all, the analogue output is what we're actually hearing after going through the amp & speakers. So based on certification and specifications, a <$10 length of USB 2.0 cable like this Belkin is just grand from the looks of it, right?
4.3 USB packet noise
We also find factors...
... less expensive USB DACs.
Sure. I can in a special case demonstrate the 8kHz packet noise. But this is far from an issue demonstrated from the DAC's analogue output. In fact, I have never heard or measured any 1kHz or 8kHz packet noise coming out of any of the DACs I have look at over the years. In fact, I would say that if anyone can measure this packet noise coming out of their DAC, then everybody should know about this and avoid this device since it's obviously poorly engineered!
5. Measure > Test > Develop...
Given the issues and limitations...Well, I can agree with the "measure > test > develop" engineering concept. Sadly, they have shown no measurements of their own in this article nor demonstrated that they've developed something that has furthered the computer audio world. If anything as I have suggested in the opening, there's just more FUD than substance constituting the core of this article.
Computer audio certainly does not stand still, it develops dynamically and with some speed.
Stereophile. "Bits are Bits"
Stereophile. "A Transport of Delight: CD Transport Jitter"
Stereophile.The Jitter Game"
... market advanced audio products.
Okay. That's nice. A few generic articles in the references. The Stereophile articles are from 1992, 1993, and 1996 by the way. Indeed, as they said "computer audio certainly does not stand still"... So why are they referring to articles from before the dawn of the computer audio era when folks were still almost universally spinning CD's, years before the first commercial SACD or DVD-A even saw the light of day? In 1996, USB 1.0 was introduced with almost no peripherals out there yet. The typical home PC was running around 100MHz rocking the original Pentium I and AMD just started to release the K5 processors. Seriously, consider the other areas of consumer electronics like reviews on computer equipment or assessment of the quality of HDTVs, is it not embarrassing that audiophile companies are still quoting articles from a long-gone era as to why we should still fear "gremlins"?
As for the manufacturer, check out the measurements of their current-model Abbingdon DP-777 DAC (~$5000) in Stereophile from 2012. Enough said.
Again, like last time I wrote about this kind of thing, shame on the audiophile press to continue to perpetuate the FUD with no evidence of commonsense or journalistic critical thinking abilities; parroting whatever the Industry throws at them.
Notice that I'm posting this message on April Fools' Day. While this post is not some kind of April Fools' prank, as far as I'm concerned, that original iFi post might as well be. Beyond the health benefits of a good laugh and not to take things too seriously, I think the spirit of April Fools' Day is a nice reminder once a year that we should maintain a reasonable amount of reality-testing in life... I would like to think that the majority of audiophiles are not of the proverbial "audiophool" variety. I really don't care or mind if anyone spends $500+ on USB cables or tweaks or whatever; as I have said before, placing subjective value in non-utilitarian benefits (like a fancy, impressive, nice-looking cable) is fine. Just be honest and rational about it and let's not perpetuate overblown anxieties...
Forget the FUD folks. Enjoy the music!