The Alien USB DAC

I spend a lot of time listening to headphones, whether it be MP3s on the computer, FM or shortwave radio, or even the very occasional computer game. I’m far from being an audiophile, let alone the sort of more-power, bigger-is-better idiot who buys kilowatt subwoofer amplifiers and things of that sort. That said, like a lot of others, I discovered long ago that many audio sources leave a lot to be desired, in one way or another. Computers, alas, are no exception.

Several years ago, I built a CMoy headphone amplifier, which might have been the best $40 I’ve ever spent, as far as electronics projects go. From the computer sound card, a radio, or an MP3 player, the results are really quite remarkable; it’s amazing, really, just how bad of sound quality most people are willing to accept, because they’ve never heard better – and how many of the problems can be remedied by an amplifier-cum-buffer.

This spring, I came across the Alien DAC (also known as “Guzzler’s DAC”) – a USB sound card, essentially, which is relatively well-regarded for it’s sound and ease of use. A kit is available, which eliminates a lot of the complexity, and is pretty reasonably priced, so I ordered one, and with a minimum of difficulty had myself a working DAC.

The Alien, however, only produces a line-level output, which isn’t really enough to drive headphones. I added a (OPA2132-based, with rail-splitter virtual ground) CMoy amplifier to mine to serve as the headphone amplifier, complete with volume control; the two fit nicely into a small extruded aluminum case a bit bigger than a pack of cigarettes, as seen below.

The rear has the USB connector and a coaxial power connector, for the amp; it’ll work from any DC supply in the 9-24v range. The front has the headphone jack, power and volume knob, and LED power indicator.

Sure, it might look nifty, but how does it work? Pretty darned well, really. Maybe even too well, in some instances. I normally despise the depth and breadth of the audiophile’s vocabulary, the fuzzy, over-excited terms like “soundstage” and “imaging” and “richness”… but I’ll grudgingly concede that the Alien adds a degree of clarity to computer audio I’ve never heard before. Insert your audio-geek platitude of choice here – “deep” bass, “clear” highs, “rich” midtones, whatever you like – this little doohickey delivers. In some ways, it might almost deliver too much – the shortcomings of some badly-encoded MP3s that were never noticeable before are suddenly all too apparent. For the most part, though, it makes even old favorites – Bohemian Rhapsody, anyone? – new again, and I’ve been having some quality time with the computer on recent evenings, re-discovering music I thought I knew before. A nice added bonus is that, for the first time ever, I now have a computer-audio source with completely inaudible hiss at any volume.

With all the surface-mount components to solder, an Alien isn’t a project for people who’ve never picked up a soldering iron before, but most experienced do-it-yourselfers shouldn’t have a problem. If nothing else, it’s neat as heck to still be able to actually put together a computer peripheral from parts, yourself; that it’s better-sounding (as well as -looking and -working) as anything I made to interface with Commodores way back in the day is simply gravy…

Published in: Geekiness, General | on August 13th, 2007| 5 Comments »

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  1. On 4/3/2008 at 1:50 pm Alex Said:

    Hey, I’ve been looking into this project alot lately. I looked into just the DAC but i really like your idea of adding the amplifier. How hard was that exactly? Any tips? or can you show a picture of the inside?

  2. On 4/3/2008 at 2:17 pm Nemo Said:

    Adding an amp to the DAC isn’t hard at all; they’re basically independent systems, built separately, then connected in the logical fashion – output left, right, and ground from the DAC go to input left, right, and ground on the amp. I used a CMoy, because it’s cheap, small, and I had all the parts – including PCB – for one laying around. You could pretty easily build a higher-end unit by substituting a Pimeta, say, and still have it fit in a fairly small enclosure.

    Tips? Not much to say, really. If I were to do it again – which I might – I’d add a second output, direct from the DAC, so that you can more easily interface it with other hardware – be it other amps, or mixers, say. Not that I do podcasting or anything, but the capability would be there. The form-factor of the Alien DAC nicely complements that of Amb’s Mini^3 amp, and mating the two wouldn’t be too difficult; I’ve looked into doing this, but haven’t fully worked out just how much of the Mini^3 board could be removed for this application; you don’t want the battery, and don’t need the charging circuit…

    I’ll see if I can whip up a few photos of the innards of the DAC and amp, but they’re really unremarkable. At one end, it’s the Alien DAC; at the other, the amp; in between are a couple of wires. 🙂

  3. On 4/3/2008 at 4:52 pm Alex Said:

    I’m doing the Cmoy first for my headphones and then probably gonna do the alien next. when you built your CMoy did you do it on protoboard or buy a PCB?

  4. On 4/6/2008 at 12:44 pm Nemo Said:

    I’ve done three – two on protoboard, and one on a PCB. I used a PCB for the one integrated with the Alien, because I had one laying around, and because it was the easiest way to integrate the fairly small, fairly high-quality Alps potentiometer I wanted to use.

    On the various hi-fi forums, there’s usually someone selling CMoy PCBs for decent prices; it’s arguable whether they sound any better than ones made on protoboard, but they certainly look nicer – right until you enclose them in a case…

  5. On 12/5/2008 at 2:45 pm BeachCat Said:

    I’ve owned the praised Oritek v4 DACs and other $500+ digital audio converters. I probably had at least $2000 worth of audio equipment sitting on my desk and I realized. This is rediculous, yes I could tell the difference between the Oritek and the Alien DAC, but it wasn’t more the a $20 difference IMO.