CG

So, again, what is the point you're trying to make? That isolation doesn't matter? E1DA uses this device, I believe, in their Cosmos ADCiso. It kills the common mode noise that you can easily measure. No reclocking whatsoever. ISOUSB211 Data Sheet

Umm... How about from here: "you keep calling it an isolator and it's not just an isolator it's a reclocker..." OK, you say it's both. My mistake. But, then, what is your point? There are other USB isolation devices out there that don't reclock. They reduce that trash level covering the floor.

Huh? I note that you've used this response in other threads in the past. Perhaps it would be helpful if you explained why you think that an Intona device, a Topping HS02, the now discontinued UpTone IsoRegen, or this Wavelength USB Spacelator are not isolators. And, why you think that doesn't matter, in your opinion. As for the rest, maybe you just are looking for an argument of some kind. Dunno. If so, please say so and I'll just declare you the victor and I'll move on.

I'm not sure where you get your information, but it is an isolator. The upstream and downstream sides are galvanically and otherwise isolated with internal transformers in the signal paths. This technique has been used in medical equipment for quite some time now. Yes, there is often reclocking performed on the signals. But, a device can do both, can't it? As for the value of an isolator, it's to minimize the effects of common mode currents, primarily in the loop between the digital source and the DAC. These currents very often cause a layer of unwanted signals and noise at the DAC output that aren't part of the original music/sound. (Contrast that to other distortions, like harmonic distortion.) It's like not getting to appreciate the nice rug on your floor because there's a layer of trash covering it. That's where measurements come in. How can you separate one imperfection from another otherwise? Audio measurements are certainly not complete in any way. So, please point me to where I ever even suggested that the human aural system is not the final and most important determinant in how an audio system sounds and is enjoyed. I will gladly publish an apology and correction when you do.

I'm glad that it's working out for you! Don't you love when that happens? Side note... I hadn't even thought about this thread since last summer, until I got a notification of Wen Hong's results in via email. But, reading through it all again, something stuck out. A number of comments were basically made along the lines of how I should measure this, and reveal that. But, I noticed that not one other person stood up and bought a device to measure and/or tear down. I'm not sure that many people here even have bought any form of test gear. (I know Miska has...) Not that anybody should be required to do either of those, at least according to me, but why are they making demands requests of others to do that for them? So they can pick on some manufacturer? So, they can beat up on me? I don't get it.

I am using a 0.8 m long Curious Evolved USB Cable between the server and the USB Spacelator and a 200 mm long Curious Evolved USB Cable between the Spacelator and the QB-9 Twenty. I haven't tried every cable out there, but that's the best I've found. YMMV and all that...

Not a JCAT or Intona, but I've tried several isolators between the server computer and the QB-9 Twenty. The UpTone ISO Regen was pretty good. (No longer made.) A Wavelength Audio USB Spacelator is even better. Again, YMMV and all that stuff. I should have a garage type sale of all the USB cables and isolation pieces I no longer use...

Personally, I've found that there are better USB cables to use with a QB-9 Twenty than an AQ Diamond. Of course, everybody has their own idea of what is better.

BTW, when I wrote "So, in an environment like that a USB isolator may have no effect" I really should have said "So, in an environment like that a USB isolator may have little or no effect."

No kidding! Isn't that exactly my point? Why post measurements that will vary from system to system, suggesting to people that some product will improve or not improve their listening experience? Is that actually useful? Measurements are certainly a very valuable tool. They'll tell you if a component works properly. They help you refine a design by allowing you to change operating conditions and circuit details to get a result you might like. But, they only give you an idea of how a device performs under the test conditions, which as you point out is quite variable and different from system to system. It all only works within the context of the test conditions. While those test results would be quite useful for me, in my system, that's quite different from posting the results taken from a very limited universe of audio systems and extrapolating some conclusion based on limited data points. And, that is what is usually done on the internet, both in articles and in forums. Repeated often enough, the conclusion becomes dogma, which is almost impossible to discuss rationally. I can point to more than one test about USB isolators published on the internet that have reached different conclusions from those you described. So, who is right? See my point? Who wants to get in the middle of that? I don't. (Note that I am in general agreement with you about the value of a USB isolator...) Anyway, that's why I don't normally post test measurements. In the past, if somebody asked whether another reader has tried a component, and I have tried it and found it useful, I occasionally posted my impression in an attempt to be helpful. I've actually reconsidered that approach and am not going to even do that any longer. It's actually not helpful to anybody and just provokes arguments, which also aren't helpful. Besides, I was just addressing the comment somebody posed that he found it unusual that readers of this site hadn't posted test results in this AS thread and along with a tear down with photographs. I gave my reasons why I wouldn't do either. Nothing more.

I have a response for this, based on my own observations and experience. They're general observations, not directed at any one individual. Measurements require test gear. Which I happen to own. But, I am generally loath to measure any one piece of gear for posting on the internet. Here's why. In order for measurements to be useful, there has to be some sort of standard. OK, just what is that? An Audio Precision test system? (No - I don't own one of those.) In this case, just what DAC should be used? The AP system is very expensive and part of the reason for that is the great lengths the company goes to in order to minimize the interaction of the test system with the device under test. Among others things, that means that the AP has superior common mode signal rejection at its analog inputs and outputs. The power system is optimized to minimize the possibility of currents conducted through the power mains. And so on. There's a reason that they have the reputation they have. So, in an environment like that a USB isolator may have no effect. A USB isolator is supposed to be a remedy for the system deficiencies AP charges a lot for to minimize. But, just who has a home audio system that has all the performance features of an AP test system? I'd like to know of even one system like that. And, what DAC should be used for this test? Isn't it almost certain that different DACs will behave differently within a system? Even the online performance tests of DACs within the high isolation of an AP test system show considerable differences between DAC samples. So, what is the standard for measurement for USB isolators? Personally, I don't want to get in the middle of unwinnable arguments like this. More than enough people are eager to insult anybody who even suggests that a product like a USB isolator might have some audible benefit. So, I'll steer clear. I did offer my own view that, for me, USB isolators are a benefit in sound quality. Earlier, I offered some examples (measurements) of why that seems to be true. If people find those observations worthy of a further look for themselves, great. If not, I'm OK with that as well. In retrospect, I shouldn't have even offered those observations. As for showing photos of the inside or even schematics, well, forget that one, too. I recently retired from a career of designing electronic equipment and systems for the telecommunications industry. Everything we built, no matter how simple, took resources of some kind. In many cases, lots of resources. The pricing of equipment is not just based on the simple bill of materials for the product. There's development costs, warranty costs, test costs, certification costs, overhead, wages for the workers, and even some profit for the corporation. And more. Yeah, all of those can vary a lot based on the industry and a zillion other factors. Even plain old greed. I was, ahh, encouraged along the way to patent whatever could be patented. I was also, ahh, discouraged from discussing anything with anybody - often even within the company itself - unless various non-disclosure agreements were in place. That was all because of the value the company put on my designs. (Other people's, too, of course.). Believe me, they didn't value me as much as they valued the designs. Personally, I'm not interested in showing off what's inside somebody else's design. They invested in it and did the work. I know that I never was happy when I found out that a competitor had copied one of my designs and tried to sell it. In my case, that didn't affect my pocketbook at all. For the audio guys, it well might. In the case of audio gear, most of the companies are small. Maybe even just one or two employees. Small companies selling small volumes of products have it hard enough without somebody "borrowing" the design and selling a competing product that they didn't have to invest time, money, or much in the way of resources of their own. In fact, I don't even post my own DIY audio design work on the internet. I've seen other guys who have done that, only to find that the work gets copied and sold. OK, that stings, even if you aren't attempting to make money at all from your audio projects. It stings because you get no credit. You feel ripped off. But, know what's even worse? When somebody credits you for a design, but then puts their own spin on it. Maybe it works better, maybe not. Maybe it's not to somebody's expectations, whatever those might be. Guess who gets the hate email or bad comments on the internet? The original designer! That's true even if the original designer never even saw that his or her work had been copied. How's s/he supposed to help with that? He or she takes the abuse without any possibility of reward or even salvation. That's crazy. Why volunteer for that? The copier always seems fine taking your work and profiting from it, but not much else. My last observation is that an awful lot of the people who ask for or demand measurements or an inside view of a product never offer to publish their own measurements or purchase a product to show off the inside, if they think that's an ok thing to do. Is that fair? Everybody can make their own rules for what they choose to do. The above are mine. One other thing. I don't go through all the threads here on AS. Indeed, I only look at small number of posts. I don't recall many photos of circuits or much in the way of measurements. Am I missing something?

I own three different types, a Topping HS02, one I built myself, and a Wavelength Audio USB Spacelator. They all measure very similarly, but they do not sound the same. I use the USB Spacelator on the "big" audio system in the living room because it sounds the best of the bunch. To me, anyway. That's the system with the QB-9 Twenty. The units I built get used with this desktop computer into an AQ Dragonfly Cobalt and some powered Emotiva monitors as well as in the workbench test set-up shown in the plots. The remainder of the units I built that were, ahh, surplus I gave away to friends. If you're inclined to argue about measurements versus sound and bias, please don't bother. If anything, I have a bias in favor of my own design, for what should be obvious reasons. But, I find that being honest with myself is valuable to me and I prefer the sound of the USB Spacelator by more than enough to keep it where it is. But, to me, any of the three sound much better than no isolator at all.

Didn't suggest or imply that you were a newbie or even not an expert. I will say that my own experience, not having to do with audio, has been than non-synchronous and uncorrelated imperfections tend to get lost in the noise of measurement, so to speak. Since they tend to be random, sort of, short bursts get averaged out because they appear once during a sweep and not again for a while. An example of that is watching the constellation of a QAM or ODFM signal on a spectrum analyzer. You can occasionally see a collapse or explosion of the displayed constellation. Since it only occurs during that one frame, it barely affects the averaged MER. But, if you were to be keeping track of the BER, you'd see errors. (One solution to that problem is to chart the MAX or peak level of the noise floor over a longer period in order to capture those randomized bursts. I've seen bursts like that caused by resonances in the power distribution system that just happen to get excited by a particular code combination getting processed. Lots of other reasons, too.) The test equipment can fool you, too. Really good test equipment puts the DUT in an ideal environment where flaws don't necessarily show up as they would in actual use cases. But, this is audio. Some aspects get judged by people listening. Other aspects get judged by people making measurements.

With 20 ENOB, maybe, doesn't that level of measurement imply a lot of averaging? So, for example, if any noise was more or less randomly distributed, it would show as a modest change in noise floor. And, how do you know the A-D contribution? I'm only asking to understand. If it's above my level or a secret of some kind, no need to reply.

How did you determine that? (Note - I violated my promise to stop posting here, but I want to understand this. So, no response from me after this. No need to cheer.)