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I mean, come on.[/size][size=small][/size]
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I bought one of these (when it had the trapezoid shaped case) based on glowing reviews. I didn't have a lot of cash in hand at the time that I was willing to sink into what was then a hobby project, and needed a more accurate DAC than I had available in my presonus firestudio mobile audio interface.[/size][size=small][/size]
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I had no idea what on earth I was doing. I was going off of REVIEWS from people who were NOT audio engineers.[/size][size=small][/size]
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The sound quality on every computer was horrible. Grating even, especially BRUTAL on female vocals. On laptops, OMG, you have got to be kidding me. I thought that THAT was "digital" sound that I was hearing.... not even close. The presonus firestudio mobile audio output blew it away for smoothness and overall correctness. All I could say for it was that one could hear SOMETHING coming out of it that resembled the original signal.[/size][size=small][/size]
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I should have sent it back. Ah, the price of education.[/size][size=small][/size]
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Today, I am hip deep in high end gear, and chock up this purchase to education on what NOT to do.[/size][size=small][/size]
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An analog circuit engineer I have a LOT of respect for looked at the picture of the circuit board after I told him I had bought one, and he laughed.[/size][size=small][/size]
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Why? It doesn't even have local power caps supporting the DAC chip or the output driver. Look at the circuit board... NO POWER SUPPLY FILTER CAPS anywhere. He said it was the most pathetic implementation of analog circuitry in a commercial DAC that he had ever seen in his entire life... making the digital wizardry a moot point. If you know anything at all about analog circuit design, look at the picture of the PC board. Tell me if you would actually buy that or recommend that to anyone. No power support capacitors on the main board. The designers had to be joking. That is the ONE place where NO AUDIO ENGINEER IN HIS RIGHT MIND WOULD EVER CUT CORNERS. It looks like an analog circuit designed by a digital engineer right out of a community college.[/size][size=small][/size]
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Think about it... USB 2.0 power is low current. It uses explicit current limiting hardware on all USB 2.0 power connections. A DAC needs to drive 96,000 instantaneously changing power settings on it's analog stage every second, not counting what the digital variations are. This requires a large, local RESERVE that can only be provided by a large, local, capacitor. The end result is that the digital circuits tap the limited power, driving down the input voltage on the power rails in an erratic pattern at very high frequencies. Couple that with the sound dampened by the lack of available current transient ability from the USB current limiting hardware which is typically ridiculously cheap and not designed for audio applications. The digital and analog in this unit share the same current limited power source. Because of the nature of current limiting on the USB, they starve each other.[/size][size=small][/size]
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Fingernails on a chalkboard and downright fuzzy is the only way to describe the result. Human ears are logarithmically sensitive to sound wave amplitude, so any erratic variations in the power source are clearly audible.[/size][size=small][/size]
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Now, one could point to that mystery Chinese black box in the middle of the circuit board next to the audio stage, which looks suspiciously like some kind of power re-generator... the ad copy claims total isolation between the audio system and the computer.... which means there is either a miniature transformer or capacitor acting as isolator and a very fast oscillator driving that isolator with pulsed DC that becomes AC on the other end of the isolator and then a set of diodes, probably a voltage regulator (maybe, but they create a lot of heat, which probably is not practical here) and a leveling capacitor. So that suggests one small leveling capacitor for the entire analog stage, which is located in the internal power supply. High end analog circuits don't generally use switching power supplies... They are noisy as hell. A tiny switcher is NOT able to provide current transients needed for accurate 100 db signal variations.... The voltage and current are not steady enough for that kind of rating. Which is why nobody in their right mind uses them in mid grade and high end audio gear. A power re-generator of this tiny size just does not have the ability to insulate the audio circuit from the power fluctuations created by digital circuitry.[/size][size=small][/size]
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The only reason I know of NOT to populate your analog stage with support caps like ELNA or Nichicon's at 10 cents a pop is to prevent your power regenerator from going unstable because it is so underpowered during power up that it cannot service the power demands of the charging capacitors... which means it cannot handle signal transients, ether.[/size][size=small][/size]
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If you happen to find yourself stuck with one of these toy DAC's, the only way to get rid of effects from cheap power supplies and demanding digital circuits loading the shared power source is to feed it a higher current stable power source. You need more current available for transients than you find on USB 2.0. Don't let the DAC fall prey to el-cheapo current limiters on the motherboard or USB cards. To stop mangling human female vocals with that tell-tale underpowered switcher sound signature of fingernails on a chalkboard, drive it with a USB 3.0 port that has a feed directly to a high end PC ultra-low ripple power supply such as a Corsair TX650 or Ultra X4. It is the only way to get stable high transient capable power into the device - either that or get a USB 3.0 hub and replace the stock power supply for the hub with a 5 volt LINEAR power supply - NOT a switcher like a wall-wart. I gave up trying to find such a thing at a reasonable price.[/size][size=small][/size]
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Your only hope is something like this: [/size][size=small]
Plugable PCI Express to SuperSpeed USB 3.0 2-Port Expansion Card for Desktops (NEC/Renesas Chipset)[/size][size=small][/size]
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Even then, it is not anywhere NEAR the same league as a Muse or HifyDiy $50-$60 Chinese PCM1793 DAC from the bay... get a good SPDIF source (many PC motherboards have good ones). If you don't have one already get any $20 sound card or some of the Native Asynchronous 24/96 USB gadgets available for around $70, and a $30 12Volt linear power supply (lots of them on amazon) and it will BLOW this Toy away for half the price. There is absolutely no comparison. The Chinese labs turn out varying quality of stuff, so you have to know your analog circuitry to know what to chose - most of them put out stuff for people who like to swap out op-amps and such. Compare the pictures of these DAC's with the picture of this DAC. Everybody else in the industry packs every chip on their circuit boards with large, very FAST capacitors, usually at least as large as the tip of your pinkie finger. This one has only tiny SMD caps smaller than a grain of rice.[/size][size=small][/size]
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To all you people who praise a device like this: you clearly have no reference points about what you can really get for $150 in a DAC. True, the DAC chip it uses is glorious. BB's are awesome. But the DAC chip is not the source of the audio quality: the analog stage and the power supply are. What you have here is something that is utterly not competitive in terms of sound quality. The root of virtually all problems in audio circuits is the quality of the power supply in the analog stage. This device tries to perform the job of a 4 pound power supply that you should be using (because they only cost about $30 retail here on amazon) in a device the size of the tip of your index finger. [/size]