If you're one of those people in search of the holy grail of audio fidelity, there's no doubt that using a PC as a complete front-end solution has probably crossed your mind at one time or another. Saving your entire music library to a hard drive and having all your favorite tracks just a few clicks away is certainly appealing, but what about the sound playback quality? Can it compete with dedicated disc transports costing thousands of dollars?

If you haven't made the move to using a PC as your front-end player, perhaps you've been deterred by the fact that PC's lack the dedicated audio engineering that we find in high-end disc spinners. Or, like me, you brought a cheap CD player and modified it to the nines and are now reluctant to invest your time in starting afresh. Such was my case until a couple of months ago when my aging Pioneer PD-S801 gave up the ghost, leaving me scrambling to find a suitable replacement.

I'd invested so much time into the PDS-801; just about every aspect of the machine had been changed somehow. Modifications to the unit included a directly heated triode output stage, fitting a low jitter master clock, replacing all audio critical electrolytic capacitors with ultra low ESR types, and replacing the stock power circuitry with ultra low noise wide bandwidth voltage regulators. Most of the inspiration for these modifications came from cruising DIY audio forums, where other obsessive-compulsive audio crazed folk like me tend to hang out.

Frequenting such places again in my time of need, I noticed that the buzzword in audiophile circles regarding ultimate digital playback now revolves around using PCs to store and playback music rather than the very best standalone transports that money can buy. It seems the buzz is primarily about three things. The first is the prospect of bit perfect data retrieval when using a suitable lossless format to burn your compact discs to a hard drive. The second is using DRC (digital room correction) to help compensate for listening room resonance and reflections. The third, using software based digital crossovers, thus overcoming passive crossover insertion losses and allowing for a more cohesive integration of drive units in multi-driver speakers.

My previous experiments using a PC with mid-budget consumer grade soundcards fell short of providing the resolution, sound staging, and detail retrieval of the modified Pioneer player. I'd put the differences down to the rampant levels of noise present inside of a PC case. After all, when it comes to soul-stirring audio reproduction, ultra low noise clean DC power is a must, and that's not something that we associate with your typical computer PSU. Computer PSUs are primarily designed to supply huge amounts of current on demand, within a certified noise band of course, but nowhere near the quality we find in a dedicated linear power supply. Hence, serious audio playback requires a soundcard designed to deal with the shortcomings of the PC's internal environment.

This leads us back towards pro audio gear used by recording engineers such as the M-Audio and Lynx range of soundcards. Most of the physical differences between pro audio solutions and your basic consumer oriented product can be put down to better components, trace routing, voltage regulation, and power supply decoupling. In addition, the pro cards feature low latency drivers that bypass Microsoft's K-Mixer and can be used with specialized software allowing all sorts of signal rerouting and manipulation. This adds up to making the pro audio offerings flexible enough for people wanting to engage DRC in a fully customized multichannel setup.

Although user reports on some of the internal pro soundcards are very favorable, my interests are stoked by external affairs. An external box presents far more interesting possibilities and flexibility to me when it comes to power supply and output stage modifications. Both are things that I'm too twitchy to leave alone and unchanged until the unit either dies under the knife or gives me what I want in terms of sonics.

One such solution revolves around using the Texas Instruments 270* range of USB - I2S and S/PDIF converter chips, which are used in several commercial outboard DACs that are rumored to be capable of upstaging even the most expensive standalone players. Better still, a range of attractively priced DIY DAC kits based on the Texas Instruments receiver chips are available that utilize levels of engineering found in commercial products costing much more. The unfortunate upshot with the TI 270* family of converters is that they're designed for two-channel use only. Those demanding external multichannel audio units will have to look towards Pro FireWire audio boxes or standalone units like the Behringer DCX2496, which has more functionality than most of us will ever need. If two-channel playback is sufficient then Logitech's Squeezebox music streamer also deserves a mention. Both the DCX2496 and Squeezebox are products that have been thoroughly adulterated by DIY masterminds and there are plenty of commercial or DIY modification packages available for both units that elevate their performance.

We aim to put some of these products to the test in the coming months while also focusing on commercial loudspeakers, disc players, and amplifiers for a range of budgets from pocket friendly to the spare-no-expense league. Today, we will take a brief look at two DIY DAC kits that we've built up and have been subjectively listening to for the past few weeks. We'll also be looking at PC-based DRC in the form of a software package called Audiolense 3.0 using some open baffle single driver speakers from 3D Sonics. If any of this tomfoolery interests you, read on....

The Test System
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  • phusg - Monday, December 15, 2008 - link

    > It'll please you all to know I have no plans to write another audio article.

    Doesn't please me at all Raja! As I said I'm very grateful for you opening my eyes to the possibilities of DRC. Shame you (or your editor?) don't fancy taking all the criticism and making a kick-arse follow-up article.

    All the best,
    Pete
    Reply
  • Rajinder Gill - Monday, December 15, 2008 - link

    I do have some work at hand that I've held back from posting mainly because it opens up another huge can of worms. The testing involved is arduous and takes up copious hours. I am in a position to make spectral measurements, although I need to confirm a few things before I'd even come close to disclosing all of the results. Initial tests show a marked difference between the 2 DAC's used in the article at equivalent levels of gain (between 1-3db at certain freq points). There's a pattern to some of it. Although, I can attribute much of this to noise generated by the amplifier due to the increased gain required by the TDA1543 (ac related hum). I have a few things I can do to cross-correlate those results though, so it's not a complete dead end.

    Blind testing has shown that human can discern down to .75db of gain. I'm not sure on the consistency of all of that as some of the blind testing involved in the research did show an element of placebo in places. Once I’ve eliminated some of the variables and more importantly tested an internal soundcard output in comparison, I might be in a position to post something worthy of reading.

    I'll probably blind test a few of the solutions I have at hand before I add anything else here though. It's very difficult to keep all camps happy, and to keep it interesting enough for me to want to commit more time to it all...lol

    later
    Raja
    Reply
  • DorkMan - Sunday, December 14, 2008 - link

    Raja, sorry if I had the Sarcasm dialed up to "11" when I made my previous post. It takes a lot of work to create an article like yours, and you did a great job. My beef was not with the quality of your work but with some of the "religion" that seems to surround this hobby. Whether it's tubes, coaxial speaker wire, or whizzer cone transducers, there seems to exist a group of people with a religious zeal for these things and for whom specs and double-blind tests are irrelevant. Whatever.

    But I commend you for your article. It was well-written, and I have no issue with your conclusions. I, too, calibrate my video-editing workstation position for response flatness.

    If you're not too turned off by all the sniping, why not do a series on audio myths? Double-blind testing of tubes and solid-state, and speaker wires?

    Anyway, hope you have a great Christmas season.
    Reply
  • audionewbieyao - Wednesday, December 10, 2008 - link

    If you're a true PC audiophile, I'll say do you best to stay away from gaming sound cards, 'cause they're just not made for audiophiles.

    I suggest try out Asus Xonar, Auzentech, Onkyo, and if possible, the new Xonar Essence STX would be the best.
    Reply
  • thietavu - Tuesday, December 09, 2008 - link

    I have myself tried to solve this "problem" for years: to create a good quality audio system around my computer. Since all my CDs and even a few of my vinyls are now digitized into almost 100 GB of data on the hard disk, the challenge was to get some good sound out.

    I kind of made a mistake by buying "too high-end" (or too good anyway) headphones (Grado SR-325) and a headphone amplifier (Musical Fidelity X-Can v3). After trying two high quality studio sound cards (M-Audio AP2496 and later AP192), I realized that the sound just wasn't what it should have been. There was always a slight "harshness" in what I heard, making the system sound a bit unpleasantly cold and mechanical.

    After a long consideration I then bought Musical Fidelity's X-DAC v3 D/A converter, plugging it to AP192's SP/DIF digital output. That made the change. The slight but disturbing harshness disappeared and some originally cold-sounding albums (like Poco's Inamorata) suddenly became both listenable and even enjoyable. And excellent recordings now sound excellent.

    Where did the difference come from? Judging by normal measurements, there should be no audible difference at all, since M-Audio card's analog output is of high quality. To me, it appears like the "magic" happens in digital->analog conversion somehow. In cheaper devices like most sound cards, that conversion seems to be somehow "rough", a bit like using a digital camera with too few real megapixels available (imagine a 10 Mpix camera with bad optics etc, and the result becoming maybe equal to a real resolution of only 3 Mpix or so).

    I admit that the differences aren't that big, and only very good quality headphones or loudspeakers etc. can reveal them. But after it is revealed, music simply sounds more like "music" in one system compared with another. After that, it's unpleasant to go back to more "mechanical" sound. But as said, everything is relative. I can enjoy an old, noisy C-cassette in an old car stereo as well, as long as the music is good! That's what it is all about: creating feelings. :)
    Reply
  • DorkMan - Monday, December 08, 2008 - link

    Sorry guys, I know many of you are really into this nitpicky level of Audio Purity. I've been into audio since the late 1960's, when I, too, was fanatical about specsmanship. Now I see the error of my ways.

    Bipolar loudspeakers have been around since, say, the 1950's. They're a decent solution as long as you can deal with room resonances, as this article does.

    But a whizzer cone speaker? When did we fall off the truck? Please tell me that the whizzer is driven by a separate coil subsystem. If not, you'll get decoupling resonances as various frequencies and these effects can change as the transducer ages.

    I went to the manufacturer website. Not embarrassed about selling speaker "ribbon" cable for $1,000? Tells me something about the company--long of PR and a bit short on electrical engineering.

    Okay, on to the amps. Tubes! The retro look! I have familiarity with tube amplifier designs and think it's great if you want odd harmonics near clipping, a bulky box that actually glows and a chance to heat a cold room at the same time. Hey, it's okay; odd harmonics sound nice--but they're not an accurate reproduction of the input signal.

    Finally, I'm all for balancing out a room--as long as the listener sits in the same spot. In a living room, every guest is going to get a different response curve, with some probably getting socked by boost when there should have been cut for that location.

    Finally, trust your microphone. If it says the room is flat, you're done. By putting in a slight bass boost, you're making the music sound good to "your" tastes, but be honest--the room then isn't flat. Might as well use tubes as amps.
    Reply
  • ackcheng - Monday, December 08, 2008 - link

    Not sure if this is mentioned before, other than Audiolense, there are a few other programs we can consider for room correction

    They are DRC which is free http://drc-fir.sourceforge.net/
    and Acourate http://www.acourate.com/">http://www.acourate.com/

    I myself use Acourate and found it a very good tool for DRC!

    But I do not think the so called DRC in Windows Vista a real DRC software!
    Reply
  • RagingDragon - Saturday, December 06, 2008 - link

    Certainly not what I expected at AT, but I enjoyed the article, and I'm OK with AT expanding it's range of covered topics (i.e. audio, digital photography, and home theatre).

    The DRC software is certainly interesting, though not really relevant to my setup (headphones). Based on manufacturer specs the TDA1543 isn't very impressive; however, the Wolfson WM8741 looks much more promising. The article's conclusions suggest the WM8741 has a wider dynamic range, flatter frequency response, and is more accurate/precise. Which is exactly what I would expect from the DAC spec sheets. I'd like to see these external DAC's compared to some high quality PC sound cards - like the Asus Xonar series, or even the M-audio revolution/stereophile cards (though if I recall correctly the DAC's in these and equivent cards from Terratec are inferior to the Xonar DAC's).

    I was looking at prebuilt external DAC's a couple months ago, and was extremely disappointed in what I found. Despite high prices most of them used cheap DAC chips which would have a hard time beating integrated audio, let alone a discreet sound card with high quality DAC's. The author's Twisted Pear Opus kit has a better DAC (WM8741) than *any* of the prebuilt external DAC's I looked at, and units equalling the Doede Douma kit (TDA1543) were ludicrously expensive.

    I'm not conviced that external DAC's and amps sound better than high quality PCI cards - and even if they do, I still don't want the extra clutter.

    Since I'm living in an appartment I use headphones rather than speakers to avoid annoying the neighbours, so the upcoming Asus Xonar Essence seems perfectly suited to my needs: stereo only (I'm using stereo headphones so surround sound is irrelevant), an extremely high quality DAC (Burr-Brown 1792A), built in head phone amplifier, swappable opamps, and "professional audio capacitors" (probably snake oil, but they won't make the sound worse).
    Reply
  • prd00 - Friday, December 05, 2008 - link

    I'd pick Onkyo USB sound card up anytime compared to those stupid creative cards. I've tried all sound cards, but right now, I've ended with onkyo. Reply
  • htgts350monaro - Wednesday, December 03, 2008 - link

    Thank you Rajinder for this, and what looks like will be, a great series of articles.

    Please be aware that despite all those who profess this to be an inappropriate article for this site that I, and I think many others, feel they are incorrect.

    Being an amateur audiophile and computer enthusiast myself this is a great mix of both my interests. I have been wondering for a while whether it would be possible to combine these interests and simplify my current combination of source components for my home theater system which I also use for critical 2 channel listening. (not ideal I know but limited space and budget regretfully denies a separate 2 channel system for me unfortunately)

    It looks like you may be on the path to solving my problem - please keep going with this. One thing I have gained from this article at least is a new interest in DRC software...

    For all thos who say that all audiophile claims are 'snake oil' I ask this - have you actually gone into a high end hifi store and LISTENED to any of the products available and done your own comparisons? Have you ever compared different DAC's/OP-AMP's in the same circuit and system with components of a high enough quality/resolution to expose those differences YOURSELF? I have and the differences can be VERY obvious, to the point that double blind listening is not needed - you would not need to double blind test two LCD's if one had half the contrast range of the other - you would be able to detect it quite easily and this can be true of audio components no matter how many tests say that the components measure the same frequency response/ dynamic range/ s/n ratio etc.

    But please go out and try it for yourself BEFORE you claim it is all bogus. (and no - not being able to hear a difference between components on your $300 minisystem or $50 PC speakers does not count!)
    Reply

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