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原文，我自己还没仔细看。
我在用iUSB和MA-1。著名的韩国卡我的小电脑没法装。
作者是pc发烧论坛的著名网友，以前看过他不少帖子。
http://www.hpsoundings.com/2013/03/2152/
IFI IUSB POWER SUPPLY
POSTED BY TED BRADY ON FRIDAY, MARCH 8, 2013
A sub-genre of this wonderful audio hobby of ours, the one called computer audio, is filled with many interesting discoveries. As a great co-worker friend of mine once said, “I’m learning something new every day….and I’m sick of it!” The computer audio hobby is something I am very involved in, especially as it relates to digital formats like DSD and the subsequent DSD-capable devices. The discoveries are indeed many, and often, yes, they get to be too much (I’m hoping to write, in the coming months, a bit about how to bypass all those frustrations) but many times they are exciting, fresh and well, even musical. Go figure.
One such discovery is the fact that computer audio has created a defacto standard in the ubiquitous USB cable and input/output. It is used for hard drive connections, powering up digital devices, and as of late, for sending 16, 24, 32 and even 1 bit music to digital-to-analog-converters (DACs) – the heart of the digital music circulatory system.
However, there are problems with picking USB as the defacto go-to cable. One, you should never use them in the above examples at the same time. This will likely cause noise, interruptions, and general chaos (i.e. if you’re gonna use a USB DAC, then use something else for your hard drive connection; FireWire, Ethernet or eSATA). The USB issue I want to address here, in this review, is another one entirely.
You see, when we got into this audio hobby, one lesson we all likely learned was to keep cables away from each other, especially power cables. Never run power cables along the floor right next to your audio cables. Duh! Well, guess what a USB cable has running within it, right alongside the audio signal? A nice strong 5V power leg. Argh! Nice going, USB guys (just kidding; this power leg is required for many of the USB applications; recharging your cell phone is a simple example).
The biggest issue with computer audio USB is that this 5V power is not only running alongside the audio signal, but the 5V power is usually generated from the computer motherboard, and it is dirty, noisy, unstable, and generally a very low quality power source.
Well, there are solutions to this. DAC and computer manufacturers have put filters in their USB signal paths, and USB cable manufacturers have put plenty of shielding in their cables. However, in many cases, these filters and shields are not sophisticated enough to keep all the noise out. Some DAC manufacturers have decided not to use the USB power at all, and instead power their USB receiver chips internally.
While other enterprising computer audio folks have created a new approach; give the USB power leg better power. Clean power! And create cables that use separate legs for power, keeping the interference as far away from the audio signal as possible – two headed “y-cables” (aka: dual conduit cables). But these solutions have their own issues: separate USB power supplies are often expensive or in the realm of DIY. And usually there are not enough USB outputs to be able to commit two of them for an individual DAC (dual headed cable).
Enter the iFi iUSB Power.
Abbington Music Research (AMR) is a highly respected audio company that builds, sells and supports High End digital and analog audio gear. Their expertise led them to understand that affordable audio is something they could do as a kind of joint venture, a sort of Far East supplies meets Western design. The press and dealer networks believe iFi is providing the market with 70%+ of AMR, for 10%-20% of the price. In the case of this USB power product, I tend to think those numbers are quite conservative.
When I first opened the iUSB Power I was struck with the Apple-like tight tolerance’d, economical, clever packaging that wastes very little space. Nice first impression. The rectangular unit is no larger than a deck of cards, and has input/power at one end, dual USB outputs at the other, with small LEDS on top that tell you the status of power, earth ground and computer connection. It’s a very simple design, but effective.
The idea is this: take your dirty motherboard-generated USB signal from your computer, use iFi’s blue USB cable (umbilical) to connect USB+power to the iUSB, then have the iUSB, plugged into a wall outlet via its specially designed low noise (iFi calls it Super Regulator) 9V power supply wallwart, clean up the power with its proprietary filtering. It then passes the clean filtered power in one of two ways: 1) through your standard USB cable you were previously using directly from your computer (in this case the cleaner power and audio signal coexist on the cable), OR 2) go out and buy a dual conduit USB cable, a sort of y-cable, that has the power coursing down one leg and signal down the other, joining at the DAC end. You see, the iUSB has dual connections at its output side, one for normal signal+power, one for just power! This solution ensures that the clean power stays far away from the USB signal until the very last moment. These dual conduit cables can be found from several sources (including Acoustic Revive, Kingrex, Revelation Audio Labs, and soon, iFi themselves). I evaluated the unit in both scenarios. In the standard single cable setup I used my go-to audio USB cable, the Wireworld Platinum Starlight 1.0M cable. In dual conduit mode I borrowed an Acoustic Revive 1.0SP dual cable.
Moreover, later versions of the iUSB packaging (including mine) included a very clever addition, one that will be sent to all early users as well, free of charge. This is a simple USB-to-DC plug cable. What is this for? Well, plugged into the USB power only output, it turns the iUSB into a universal 5V power supply for any piece of electronics that needs clean 5V power. This category includes Logitech’s Squeezeboxes and several portable DACs. In fact, my own music server setup uses a SOtM USB card which can be separately powered externally, and so I demo’d the now-becoming-a-Swiss-Army-knife iUSB power supply as a simple direct 5V power supply for my SOtM card too (instead of using it between pc and DAC). More on that later.
So….what DACS benefit from clean USB power? Some would say all of them, but it must be repeated that many DACs do not require power from the computers own USB cable, and for those setups the iUSB may not provide a lot of benefit…but remember it also isolates earth ground..so I would not rule out those DACS having some beneficial handholding with this unit. Often being able to lift ground can reduce noise that crept in from elsewhere in the system. A simple flick of the iEarth switch will tell you.
My go-to DAC currently is the Meitner MA-1 DSD-capable DAC. It falls into the category of those dacs using the computer’s 5V power to identify and complete the handshake. The iFi has a legit target!
Scenario one: standard setup with a single USB cable used for audio. The iUSB sits between my Win 8 minimalist music server (USB output from SOtM PCIe USB card into the iUSB via the supplied blue umbilical). The Platinum USB cable is then connected to the iUSB and into my DAC. Wallwart plugged into a power conditioner.
Scenario two: same as above, except swap out Ted’s Platinum cable for a dual conduit Acoustic Revive 1.0SP cable, plugged into the two USB ports (power only leg is identified by AR and plugged into power only port).
Scenario three: iUSB is used simply to power the SOtM card, using the USB/dc plug into the card’s external dc port. My Platinum cable is plugged into the SOtM card as usual. Wallwart still plugged into a power conditioner, but no other USB cables or umbilicals needed or used.
In all three scenarios the Meitner DAC recognized the server and its driver without fail. The iUSB did not interrupt or cause any confusion. Spoiler: in all three scenarios music was improved!
I used a host of different music to evaluate this Swiss Army knife unit, including redbook, 24/192 tracks and native DSD (DSF files). But one very specific album seemed to easily show the benefits of the iUSB, and also show the gradations of improvement among the scenarios described, so I will focus on this album. By the way, all the comments held true for almost all the music sampled. Caveat: only highly bombastic recordings were difficult to discern, but it was easy to understand once I got a hang of it.
In 1988 the Canadian alt-folk-rock Cowboy Junkies recorded an album in Toronto Ontario’s Church of The Holy Trinity (they came back 20 years later to reimagine it with help from some friends, but that is a review for later). it is called The Trinity Sessions, and was recorded using a single Ambisonic microphone. Subway noises and other anomalies can be heard, depending on one’s system resolution. I know this album intimately – or so I thought.
The injection of the iUSB into my system brought about a completely new way to hear this album. The reduction of the systems overall noise floor was a revelation, especially for things like timbre and tonality! The harmonics shone through like never before, bringing about a change in timbre from guitar to 1978 Martin (making that up, but you get the idea). It goes without saying that the ambience of the church came through better, but the major benefits were micro-details, harmonics and a better cleaner sense of Anton’s bass. Margo’s breathing, before her first accapella words in “Mining For Gold”, were never quite heard like that before (I don’t do a lot of headphone listening, but the general feeling was that kind of revelatory details when one puts on a great set of phones and hears the recorded space load the inside of your head before a note is struck).
Scenario two was most revelatory, and the likely reason was due to the dual conduit design of the cable. I know AR’s normal single cable sound; it is not that dissimilar to my Platinum cable. This was quite a bit better. Scenario one, however, was a clear second place winner, which surprised me. I assumed a direct connection to my SOtM card, something most audiophiles couldn’t do in their server setup, would trump using an umbilical, etc. It didn’t. The clarity and pace of the music was clearly better with the iUSB between the server and the DAC, and I can only assume that the iEarth grounding mechanism must have something to do with it. Don’t get me wrong, scenario three still beat doing nothing, but utilizing all aspects of the iUSB was a no-brainer in my setup.
Oh, all of these improvements cost $199 (plus a new USB cable if you go for scenario two). And as I mentioned earlier, the noise floor improvements to tonality, timbre, bass definition and overall air/depth were obvious in most music I demoed over the past month. Only bombastic loud classical, big band and rock epics were somewhat difficult to discern. So what! My smokey acoustic jazz never sounded so smokey…oh and the smoke is easier to identify… now where did I stash those Oreos??
Thorsten Loesch and his team at AMR/iFi are on to something very good, very inexpensive, and very focused. And us cheap audiophiles are the ones who stand to gain. They are bringing out a DAC, a phono stage and likely other amplification, etc. Keep an “i” on iFi. They might just change the paradigm of what we used to call cheap cheerful hifi.
[ 本帖最后由 yamuling 于 2013-3-29 15:51 编辑 ] |
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发表于 2013-3-29 15:45:07
提升卡
变色卡
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我后来仔细看了下,似乎还是论坛那些评论意见,并没有太多新意.
