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Test Setup: Cables, Software, And Tracks

What Does It Take To Turn The PC Into A Hi-Fi Audio Platform?
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Cables and Connections Used

For the O2+ODAC and the DAC2, we used vendor-supplied USB cables.

The Sennheiser and AKG headphones both relied on stock cables.

Four identical Hosa 10-foot TRS female-to-TRS male extension cables were used. For the O2+ODAC and Realtek ALC889 codec, which do not have TRS jacks, a Hosa TRS female-to-3.5 mm RCA male adapter was used. These are not exotic components; the cables are $7 each and the adapters are $3 each.

Here's an important question, though. Why use extension cables at all? Why not plug headphones directly into device jacks?

The reason has to do with our blind listening process. Extension cables essentially render interconnect noise the same (when the headphones are switched from one device to another) and require no moving around on the part of the test assistant performing the switch. It'd be hard to perform a truly blind test if the assistant had to get up, walk around to the back of the PC to plug into a sound card, and so on.

I believe (until I'm otherwise proven wrong) that the cables and adapters are audibly transparent. If you'd like to read a serious study on the effects of cables on audio frequency response, we recommend this article.

Music Formats

We classified sources into three categories:

Compact Disc Digital Audio (CD-DA)

These tracks are encoded with the common pulse-code modulation (PCM) scheme used in standard audio CDs. The format is a two-channel signed 16-bit linear PCM at a 44.1 kHz sampling frequency.

As a bit of trivia, the main reason why CD audio is sampled at 44.1 kHz is that the corresponding Nyquist frequency (the highest frequency that can be captured using the sampling rate) is 22,050 Hz. Hence, CD audio is designed to capture and represent all frequencies humans can hear.

What's more, sometimes this format is referred to as "Red Book" from the color of the binding book containing its technical specification.

The reason why CDs are designed to hold 74 minutes of audio is said to be less technical and more "human"; reportedly, Sony's president Norio Ohga wanted to listen to Beethoven's entire 9th symphony in his car.

Benchmark DAC2 HGC in operation. The LCD tells us it's configured for 16-bit/192 kHz. The smaller O2+ODAC is on top.Benchmark DAC2 HGC in operation. The LCD tells us it's configured for 16-bit/192 kHz. The smaller O2+ODAC is on top.

DVD-Audio (DVD-A) and DVD-Recordables (DVD-R), including PCM files (typically .WAV)

These are tracks that have higher word length and sampling frequency than "Red Book" CD audio.

While 24-bit recordings are relatively common in the recording studio, they tend to be used more for headroom in editing than an actual audible benefit. We've never seen a properly-conducted blind test where individuals could reliably tell between 24- and 16-bit audio. With that said, "audiophile" recordings made available at the native 24-bit, though not very popular, do exist.

Higher sampling frequencies than 44.1 kHz again provide more headroom for editing; the actual benefit in terms of audio quality is the subject of much debate. The ultrasonic frequencies that such high sampling frequencies collect are inaudible, unless you happen to be a dog (which can hear up to 60 kHz), cat (79 kHz), or a bat (up to 200 kHz). And that's assuming that your speakers/headphones can play those higher frequencies correctly. They certainly aren't designed to. In fact, the harmonics from those frequencies can actually result in lower fidelity.

We sourced our DVD-A files as uncompressed WAVs from www.hdtracks.com.

Super Audio CD (SACD)

Direct-Stream Digital-encoded audio takes a very different approach than multi-bit PCM. DSD has a word length of only one bit and a sampling frequency of 2.8224 MHz. It is a pulse-density modulation scheme. The benefits and limitations of DSD versus PCM are, not surprisingly, the subject of much debate and there is really no consensus, even among academics, on which is superior.

Although DSD content is rare (SACD never really took off), so-called "native DSD" digital-to-analog-converters appear to be popular in the audiophile community. Mytek, in particular, is pushing the format.

Some SACDs contain multi-channel tracks. The most famous one is likely Pink Flyod's The Dark Side of the Moon, which contains six channels on a "hybrid" disc.

Of the devices we're testing, only Benchmark's DAC2 supports DSD natively. So, we'll reserve a separate section of this article to delve into it.

Test tracks

In our choice of test tracks, we wanted to represent a wide variety of genres and musical format options. Obviously, how well a particular track was recorded influences the listening experience massively. So, our selections were picked because, in addition to being enjoyable, they were also recorded well.

Album / Track / Artist
Format
Comments
Skyrim Official ST / Dragonborn / Jeremy Soule
CD-DA
(16/44.1)
 Nothing screams Dovahkiin! like Jeremy Soule's signature soundtrack. Sung by 90 voices at the same time (30 people singing three times then mixed together), this dark, gloomy track is the ultimate test of deep bass.
Delta Machine / Soothe My Soul / Depeche Mode
CD-DA
(16/44.1)
Electronic music and vocals at their finest. This is one well-recorded track. Also available in DVD-A 24/44.1 format.
Inhuman Rampage / Through the Fire and Flames / DragonForce
CD-DA
(16/44.1)
Two-hundred beats per minute and rapid twin guitar solos by Herman Li and Sam Totman of power metal band DragonForce. One broken guitar string in the process.
Random Access Memories / Get Lucky / Daft Funk feat. Pharrell Williams
DVD-A (24/88)
Smash pop hit. A well-recorded track available in DVD-A format.
Symphonic Dances / Andante con Moto / Rachmaninoff [Eiji Oue w/ Minnesota Orchestra]
DVD-R
(24/176.4)
A beautiful classical piece recorded in 24-bit at 176.4 kHz, edited and mastered at 88.2 kHz, and re-transferred to 176.4 kHz
Thriller / Billie Jean / Michael Jackson
SACD
(DSD64) and DVD-A (24/176.4)
Thriller is the most-sold album ever (100 million copies sold worldwide). If you haven't been living under a rock, you know the track Billie Jean from this album. This particular SACD version is reportedly created by Gus Skinas from the original SACD cutting masters.

Player Software and Configuration

We used foobar2000 v1.3 beta 7. It's free, it works, and it doesn't mess things up. It's doesn't look cool, but that doesn't deter us. Benchmark wrote a pretty good article on how to configure it.

In short, configure outputs as WASAPI devices, set the output data format to 24-bit (the maximum supported by the devices we're testing), set all volume levels to max (0.00 dB), turn off Replaygain, and bypass all audio plug-ins. Note that devices in WASAPI mode will default to 16-bit operation if 16-bit content is played, ignoring the 24-bit setting. That's a good thing. It means that 16-bit tracks don't get padded to 24-bit, which would be undesirable.

It doesn't really matter if you configure outputs as WASAPI, KS (Kernel Streaming), or ASIO devices, as long as you are consistent. Each mode bypasses the Windows mixer, resulting in a bit-perfect stream to the DAC. The only mode you want to avoid is Direct Sound, which doesn't bypass the mixer.

Although it takes an extremely convoluted process to get working, foobar2000 is one of the few players in the world that can natively play DSD files on supported hardware. A notable alternative is JRiver Media Center, which has a free trial, but isn't free per se.

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Top Comments
  • 12 Hide
    SuckRaven , February 25, 2014 12:29 AM
    Bravo ! Awesome, and a very thorough review. Even though as you mention, audio gear is not usually the forté/emphasis of the reviews here, it's refreshing to have someone at least try to cut through the (more often-than-not) overpriced arena of bullshit that is the field of "high-end" audio. I applaud the review, and the effort. Keep up the good work. More please.
  • 11 Hide
    shahrooz , February 25, 2014 1:05 AM
    this article just won Tom's Hardware Readers Elite award
  • 11 Hide
    kitsunestarwind , February 25, 2014 12:52 AM
    The biggest thing I have found for the PC is no matter how good your DAC is , if your speakers and AMP are crap, then it will never sound better.People spend big money on DAC's and forget that you need a high Quality amp with very very low THD (total harmonic distortions) and a very good set of Full Range speakers with high sensitivity if you want good sound, instead of crappy (albeit expensive) computer speakers especially sets with a sub.
Other Comments
  • 12 Hide
    SuckRaven , February 25, 2014 12:29 AM
    Bravo ! Awesome, and a very thorough review. Even though as you mention, audio gear is not usually the forté/emphasis of the reviews here, it's refreshing to have someone at least try to cut through the (more often-than-not) overpriced arena of bullshit that is the field of "high-end" audio. I applaud the review, and the effort. Keep up the good work. More please.
  • 8 Hide
    PudgyChicken , February 25, 2014 12:44 AM
    Just wondering, why not test a Creative X-Fi Titanium HD or something like that alongside the ASUS Xonar? It would be interesting to see some of the differences between different PCIe sound cards in this matchup. However I understand that what you were really going for was showing the difference between price point and form factor at the same time, so perhaps not testing two PCIe cards makes sense.
  • 11 Hide
    kitsunestarwind , February 25, 2014 12:52 AM
    The biggest thing I have found for the PC is no matter how good your DAC is , if your speakers and AMP are crap, then it will never sound better.People spend big money on DAC's and forget that you need a high Quality amp with very very low THD (total harmonic distortions) and a very good set of Full Range speakers with high sensitivity if you want good sound, instead of crappy (albeit expensive) computer speakers especially sets with a sub.
  • 11 Hide
    shahrooz , February 25, 2014 1:05 AM
    this article just won Tom's Hardware Readers Elite award
  • 1 Hide
    maestro0428 , February 25, 2014 1:27 AM
    Wonderful article! I love listening to music and do so mostly at my PCs. I try to set up systems where audio is important in component selection. Although we all love drooling over expensive equipment, many times it is not all that necessary for an amazing experience. I'd love to see more! Including smaller, studio speakers as I believe that speakers/headphones are the most important part of the equation. Keep up the great work!
  • 5 Hide
    blackmagnum , February 25, 2014 1:28 AM
    Don't forget that for PCs: the hardware is as good as its software (drivers).
  • 0 Hide
    Someone Somewhere , February 25, 2014 1:43 AM
    Agree totally with this. It always annoys me when people say they're spending over $100 on a sound card, especially when it turns out that they're using Optical out, and the whole thing is basically moot.I now have a nice source to link to.
  • -1 Hide
    1zacster , February 25, 2014 2:01 AM
    The thing is you can't just pick up two sets of good headphones, try them on different DACs/AMPs and expect to hear major differences, it takes longer than 5 minutes for your ears to adjust to newer headphones and for the differences to actually show. This is like taking food from Left Bank and then bringing in a bunch of hobos and asking them tel tell the differences between the foods.
  • 1 Hide
    dogman-x , February 25, 2014 2:34 AM
    I use an optical cable from my PC to a home theatre receiver. With this setup, stereo CD audio content is sent as raw PCM to the receiver, not compressed into DD or DTS. These days you can buy a very good quality home theatre receiver for less than $200. Audio quality is outstanding.
  • 1 Hide
    Memnarchon , February 25, 2014 2:50 AM
    I would love to see ALC1150 in these tests too, since its widely used at most Z87 mobos.
  • 0 Hide
    outlw6669 , February 25, 2014 2:56 AM
    Excellent in depth review Filippo! It is good to see a bit of Tom's roots shining through after all this time :) 
  • 3 Hide
    loosescrews , February 25, 2014 3:01 AM
    I would have liked to see some hard to drive planar magnetic headphones in the mix (maybe some of the Audeze LCD-X or LCD-XC headphones or HiFiMAN something) and also a cheaper DAC/Amp solution like Maybe the Schiit Audio Modi + Magni or Vali. Another nice addition would be the Creative Sound Blaster Z Series ZXR with its TI Burr-Brown DAC.
  • 4 Hide
    BrightCandle , February 25, 2014 3:17 AM
    Can we get game surround sound audio tested as well? A lot of the reviews recently are focussing on sound quality differences in music but as you have determined there really isn't any difference there. But there is a clear difference I can hear in the comparative videos of battlefield with cmss, sbx pro, razor and realtek on youtube videos and the different surround sound effects really do seem to change positioning quality. This remains the only reason I think a sound card is worth it over realtek but it would be good to get to the bottom of whether its just EQ or its genuine quality differences related to the HRTF or something else.
  • 0 Hide
    bstaletic , February 25, 2014 3:27 AM
    Great article. I also came to similar conclusions. I had bought High Resolution Technolies Musicstreamer II 2013 edition for ~$140and an Asus (I don't remember which one) for ~70$. I have technics SU-V8 amplifier and Wharfedale E50 speakers (cool stuff, look it up). Muscistreamer made bass a bit better (though not everyone could hear the difference) and now I say it was a waste of money. Asus on the other hand could make a difference if you set it up correctly, but you have to do it for every album so forget about shuffle. Only DAC I'm willing to hear is DACmagic for ~$400 and I doubt I'm going to be impressed.Conclusion: Buy any PC (the cheaper the better), and spend the rest of money you have on speakers and amplifier. Also make yourown cables.
  • 4 Hide
    ilovetea , February 25, 2014 3:34 AM
    What's the purpose to invest into some special pc hardware, if major reciever brands have digital inputs and also usually unify inflows of audio through digital filters? This makes the reciever to serve as DAC both supporting and limiting the final quality.
  • 3 Hide
    Someone Somewhere , February 25, 2014 3:53 AM
    Quote:
    What's the purpose to invest into some special pc hardware, if major reciever brands have digital inputs and also usually unify inflows of audio through digital filters? This makes the reciever to serve as DAC both supporting and limiting the final quality.


    What I have been saying for quite a while.
  • 5 Hide
    vmnej , February 25, 2014 3:57 AM
    Electronics are negilable. The hard part ist turn ing the electrical signal into a mechanical signal (sound waves). That' why most of the money should go into the speakers and then maybe room acoustics. I highly recommend a pair of Nubert nuPro speakers.
  • 2 Hide
    gaymer1984 , February 25, 2014 4:01 AM
    I have a challenge to lay down for the writers of this article as an audiophile.Nothing you have particularly referred to can be contested; you do get more features with more expensive hardware, but price isn't necessarily an indicator of quality and it is high quality audio you are looking for, not necessarily the price point. That assumption doesn't work with sound cards as the first point in the signal path to the speakers.My challenge is this: compare your ALC 889 to an E-MU 1616m PCI-E. The quality of the DACs is higher on this £250 board than other PC sources I've heard myself, and you aren't spending £2,000 to get there. I challenge you to NOT find a difference. Don't change anything else in the signal path - keep the cable that feeds to your amp, and the speaker cables the same. Then listen to audio you know very well, and you know has been recorded well. This is harder to find with current music.You aren't looking for things to sound "better" or "louder", you are looking for greater detail. A better stereo "image" as it is called, where you can place instruments being reproduced by the speakers in a notional 3-D space. That is the mark of "good" audio.I ask you to accept this challenge because without following up this statement of $2 is as good as $2,000 you will potentially mislead budding enthusiasts down a misguided path.
  • 0 Hide
    martel80 , February 25, 2014 4:10 AM
    Why not include readings from the RightMark Audio Analyzer? They don't tell you anything about how it sounds but still...
  • 6 Hide
    Someone Somewhere , February 25, 2014 4:11 AM
    Oh, great.

    Do you believe that the E-MU 1616m is significantly better than their $2k amp? If not, then they're still not going to find a difference.
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