review33.com: 影音天地: HiFace Professional

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[#1] HiFace Professional HiFace Professional, a mod in Japan: http://www.aurorasound.jp/hiFace.html		CKKeung 正式會員 218.xxx.xxx.175	2010-12-02 07:12

[#2] HiFace Professional
no external power supply circuit, not a good mod, 29800yen, better buy hiface evo

batmanames04

正式會員
180.xxx.xxx.246

2010-12-02 08:39

[#3] HiFace Professional
How can it be 'professional' without external power?

CKL2

正式會員
143.xxx.xxx.2

2010-12-02 16:52

[#4] HiFace Professional
How can it be 'professional' without external "power?" by CKL2
可以，Diverter都係用USB電，並非設計者唔識搞external power，而係設計工程師覺得插牆既電一樣好污糟，而USB電同牆插上既電一樣可以淨化，但USB電仲有其他好處牆插畀唔到，以下係網友對佢使用USB電的質問及回應。

JayDee好有料，連Empirical Audio既設計師走去個Forum度同佢單挑最後都變成左技術交流。

提問：Originally Posted by gevorg
Even Empirical Audio's basic $700 Off-Ramp (which is an overkill for many audio systems) has a 12V DC input. No need to attempt to make USB power cleaner.
-----------------
設計師JayDee回應：
I'm really glad you brought this up, because this is an audio sacred cow that desperately needs to be slain IMHO. If there's anything I pride myself on as a designer, it's dealing with power supplies. I think a good power supply is the single most important design feature of a piece of audio gear. Whether it's an amp, DAC, converter, or whatever - at the end of the day all audio gear is just a modulated power supply. Does it surprise you or seem hypocritical of me to say that when I'm using the USB bus for power? Can’t figure out why I didn’t opt an outboard supply? Read on.

Friends, I'll just lay it out for you, and I of course qualify this as my opinion with no desire to offend. I think there are four reasons outboard power supplies are so popular in our industry:

1.) It provides the illusion of additional value - hey, there's another box there, right? Two boxes must be better than one, no?

2.) It can look cooler or more sophisticated. Sure, I'll even admit that. Especially if the umbilical cable looks cool, with some boss connectors - there's just more tech love there.

3.) The claim is often made of improved shielding and / or vibration isolation. There may be some merit to the shielding argument, but there's no reason that can't be done inside the main device. Same goes for vibration control; I can't see how a separate enclosure is inherently better in this regard. In the case of the Diverter, all the first-stage filtering and conditioning occurs on the bottom side of the PCB, which is completely shielded from the top side where the conversion occurs. And as for vibration control, that’s an integral function of the machined chassis and the special damping feet. Also, all of the bypass caps are non-microphonic film types.

4.) It's another SKU to sell. More parts, more things, more upgrade paths, another sales opportunity. Start the customer off with the basic power supply, and sell them later on the ultraluxe model. That's not inherently bad or deceptive, it's just good business, and perhaps gives the customer the ability to start off at a lower level and upgrade when finances improve. But it doesn't mean it's better from a technical point of view, and I will always do what I feel is the best technically, regardless of whether it might be a missed future sales opportunity.

I have two objections to outboard power supplies:

1.) The power delivery path is longer, with a higher current loop area, and therefore has higher impedance. An umbilical cable of some kind must always connect the supply and the load together. I spend a lot of time and effort in minimizing the impedance of my supply, so why would I want to go deliberately go and add some? I should note here that impedance, in the form of inductance, is often and legitmately used in power supplies for filtering, and I sometimes use this technique myself. But you want to apply such a technique in the right place. In the case of an outboard supply, presumably you have the main voltage conversion components and bulk capacitance remotely, and then the local regulation in the powered device. A low impedance connection between the bulk capacitance and the downstream load is generally desirable. I suppose someone could account for the umbilical as part of the L section of a Pi filter, with the second-stage shunt caps on the receive side, but I’ve never seen that done. In short, I just don’t see any compelling reason to offer an outboard supply, other than the fact that nearly everyone seems to consider it de rigueur.

In the case of the Diverter, the low-ESR bulk capacitance is attached directly to power and ground planes. The audio community often touts the benefits of low-ESR capacitance, as if that attribute imbued the capacitors with some transcendent properties that are always in effect regardless of how they're used. If your expensive low-ESR caps are many inches away and connected via an umbilical, you just nulled much of their potential benefit.

2.) Because the supply has an umbilical cable, you've just unwittingly attached an antenna to it, which is ironic given that one of the presumed benefits of an outboard supply is that it is quieter. That's right - a new path for egress or ingress of EMI/RFI. You can shield the cable, sure, but why not just get rid of it altogether?

In the interest of nipping a flame war in the bud, some of you might be objecting that you’ve heard the benefit an outboard supply can impart. Sure, and so have I. But in order to do a meaningful comparison, you’d have to listen to a device with an outboard supply, and then with that same supply built internally, yet with all the same shielding the outboard one featured. I have done that, I the internal one wins every time. So my point isn’t that outboard supplies can’t be a legitimate upgrade over stock, just that as I designer I will always choose to build that upgraded supply internally so as to obtain the shortest possible power delivery path. In the upcoming Decoder DAC, for instance, the power supply is part of the overall device and isn’t outboard in the traditional sense, but it does reside in its own machined cavity, with 360 degree shielding. It gives me all the shielding benefits of the outboard supply, but has a power delivery path of less than one inch. Granted, it can’t be field upgraded with a new supply, but doing it right the first time is a more than acceptable tradeoff to me.

I want to state unequivocally that in my opinion, the best power supply is the most compact possible one, with the lowest noise and output impedance, that is as physically close to its load as I can possibly make it. And that's exactly what I've done in the Diverter: there are multiple, agressive stages of filtering, there are three separate supplies using the lowest-noise regulators on the market, and there are three, large multi-element, computer-optimized bypass networks that connect directly across the power and ground planes.

In the case of the USB bus supply specifically - a lot of criticism has been heaped upon it because it comes from the computer, a worldwide EMI/RFI pariah. And I don't disagree on this point; the USB Vbus supply is not what anyone would call an "audio-grade" supply. But it isn’t exactly Satan’s own voltage source, either. I can surely turn it into an audio-grade supply, just the same as someone can turn an AC supply into something worthy of the finest audio electronics.

Look, a power supply is fundamentally a potential difference (voltage) and a means for current to flow. Give me that, and I'll work with it from there. The USB supply isn't any worse than working with an AC wall supply that has all kinds of garbage riding on it; in fact, it at least has the advantage of tighter regulation! An entire cottage industry has sprung up around cleaning up and purifying AC power, and rightfully so. Few people seem to question the benefit that a good AC power delivery system can have. Can't some of those same techniques be efficacious when dealing with the USB power supply? As long as I have sufficient voltage and current capability, adequate PCB area and parts budget, I could power the Diverter from the magneto in your lawnmower's Briggs & Straton and have it sound good. But some of you won't believe this, because you've heard and repeated the myths so many times that they've become immutable gospel. Electrons coming from blessed and sanctified outboard sources are good; electrons coming from nasty, evil, wicked PC supplies are hopelessly tainted and incapable of redemption.

Another sacred cow is that of the "high-current" supply, and that does have legitimate application in the case of something like an amplifier. I'm sure there are some who think a big 300VA toroid and a few hundred thousand microfarads of capacitance would convey an aura of legitimacy to the Diverter, but I just don't agree. Again, if I were to do that and build it to the same standard as the current product, it would be unnecessarily larger, heavier, and more expensive. With half an amp of capability, the USB bus is more than robust enough to supply the current pull of the Diverter, which is less than 50mA steady-state, and has a very well-controlled and brief inrush current of 450mA peak on startup. The degree to which high-current supplies improve low-powered device like preamplifiers or digital electronics isn't so much anything to do with their actual ability to deliver sick amounts of current, but rather their low impedance and noise signature.

by JayDee

http://www.head-fi.org/forum/thread/445553/sonicweld-cryo-parts-diverter-96-24-usb-to-spdif-review/90

最後修改時間: 2010-12-03 07:42:58

sky176

正式會員
119.xxx.xxx.115

2010-12-03 07:27

[#5] HiFace Professional
Never under-estimate Japanese CAS audiophiles & gear manufacturers. Many of them have more CAS experience & knowledge than us.

最後修改時間: 2010-12-03 10:48:17

CKKeung

正式會員
210.xxx.xxx.224

2010-12-03 10:47

[#6] HiFace Professional
for small power consumption device, the cleanest power is from battery,

sure better than diverter

batmanames04

正式會員
180.xxx.xxx.195

2010-12-03 12:05

[#7] HiFace Professional
正

tingmoon

會員
219.xxx.xxx.138

2025-02-20 12:42

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