A video of Michael Goodman describing the products at THE SHOW Newport

A Video Review of DACport LX from AudioHead!

Noise Plot

DACport features an extremely quiet headphone amp. Most reviewers agree that with no audio, the output is "pitch black" (nothing can be heard in the headphones). We took an FFT plot of the steady-state noise pattern in the DACport's headphone amp. The plot clearly demonstrates why the output is perceived as "pitch black"—DACport's self-noise is just above -130dB across the most sensitive range of the audio spectum. DACport LX is even quieter. This level of noise performance is unheard of in products of this price range. Click the plot for a larger version.

Suggested 24/96 Sources

DACport gives you access to the world of 24/96 music, so where do you get this music to listen to? Here are some reputable record labels, which offer high resolution files for purchase and download online. CEntrance is not affiliated with these vendors.

Breathe new life into your existing MP3s

Keep in mind that you don't need to run out and re-purchase your entire music collection in hi-res formats. DACport is also great with standard-resolution material, such as your existing CDs and MPs because it adds greater clarity to the music. You will never be able to go back to the built-in audio jack on your computer! With DACport, even compressed files come to life letting you hear new detail in your favorite recordings, offering wide soundstage, incredible dynamic range, extra resolution and crisp definition in all frequency bands.

Sound Quality Evaluations

Listening Tips

In general, we recommend sticking to the material you like and know well when comparing different pieces of playback equipment. This will remove the variable of unfamiliar music.

Unless you majored in jazz or grew up in Latin America, you may appreciate a quick excursion into the wonderful world of Afro-Caribbean percussion. All of the featured instruments share a single trait - they propel the music forward with a sharp, defined, wide-band pulse. Another thread that unites these instruments is their ability to challenge the jitter performance of a Digital to Analog converter. While the bass and midrange instruments will also come forward and become more defined in a high-quality DAC, latin percussion can't be fooled - it either sounds right, or it dies in the mix to the point of being unrecognizable. So, put on some brazilian grooves or salsa music, or even smooth jazz, which is full of latin percussion. Close your eyes and answer a very simple question - "Do I want to live there?" If the music sounds right, you will want to be transported into the recording. A similar technique is used by fine art appreciators. A good painting draws you in, wants you to stay for awhile. A good D/A converter does the same. DACport is designed for hours of operation without listening fatigue.

Here are some music suggestions from my experience. Many people use Donald Fagen records for rich instrumental arrangements that still leave a lot of space in the music due to moderate amounts of compression (Morph The Cat, Kamakiriad, Nighfly). I would consider anything recorded by Bruce Swedien (he worked on most Michael Jackson albums). And in that same family, pretty much anything by Quincy Jones – for his immaculate taste in production quality. Look into Chuck Loeb, Fourplay, and Brian Bromberg. I would also recommend Pat Metheny's "We live Here" album, but that’s just a start… Let your ears be the judge!

Jitter Management - Debunking the Asynchronous Myth

Some manufacturers may lead you to believe that Asynchronous USB transfers are superior to Adaptive USB transfers. This no more true than saying that you "must" hold the fork in your left hand. If you know what you are doing, you will feed yourself with either hand.

The USB argument comes down to jitter management and goes as follows: In Asynchronous mode the device is the clock master. In Adaptive mode, the computer is the clock master. Either way works fine, if correct design principles are followed. Here is the tricky part that often gets omitted: No matter which side is the source of the clock (PC or DAC), the two devices are still connected by the USB cable and the digital data on that USB cable is always irregular because the computer is involved. Computers do many things at once and end up sending data over USB in irregular intervals, no matter who is the clock master on the bus. This irregularity causes jitter. So, there is no jitter-free solution, just like there is no dust-free house. Irregularity always creeps in and needs to be actively managed.

Here is where the Asynchronous vs. Adaptive argument breaks down: In either of the two clocking schemes, jitter is present during transmission. It's inevitable and also ok, if it is properly cleaned up prior to the D/A conversion, where it matters most. Neither clocking scheme is superior and both are capable of performing well if you know how to reassemble the bits prior to the DAC. Now, how do you actually do that? There are many ways, the oldest and simplest of which is buffering. Irregular data comes in, regular data goes out. The most important part is to make sure that samples leaving the buffer on the way to the DAC are clocked accurately. DACport employs JitterGuard™, a proprietary two-stage clock management system that does just that - cleans up the jitter on the USB bus so that samples are virtually jitter-free at the D/A conversion point. The result is a natural response, crisp definition, extra resolution and wide soundstage.

Analog Performance

No Volume Slider

Because we don't let Windows do any processing on the audio, we also disable the Windows Master Volume Control slider. This is done on purpose to give you the most truthful audio representation with no interference from the OS. Please use the analog volume control on the DACport to control volume.

Warm to the touch

DACport has a Class A headphone amp which runs warm to the touch. Class A headphone amps consume higher power but give you lower distortion in exchange. Don't be alarmed when you pickup your DACport after a half hour of listening - it will be pleasantly warm, but not hot, so no worries.

Part choice

People often ask about the parts inside DACport. We feel that the right way to evaluate the product is by the overall sound quality rather than by part names. Consider that two designers can make two very different products using the same part. It's the overall design that matters, down to the traces on the PCB, RF coupling, shielding, grounding, biasing, powering, etc. We use special design enhancements in our products and pride ourselves in our ability to get the best quality from every part, so comparing on part names alone is useless. At the end of the day it's all about sound quality, so go ahead, get yourself a unit and listen - if you don't like it, we will refund your money.

Applications

DACport is ideal for travel as a portable, audiophile-quality sound card. Pack up your favorite headphones and relax – watch Blue Ray movies on an airplane, listen to hi-res music at a hotel room, at work, or in a coffee shop. DACport has been dubbed “the ideal coffee shop rig” by Jude Mansilla of head-fi.org because it transforms your portable listening experience, upgrading it to High Resolution. But Hi-Fi on-the-go is only one way to use it. DACport is equally comfortable at home, as part of a permanent audio setup.

We designed DACport’s headphone amp in such a way so you can easily connect it to an external power amplifier and a set of speakers. To do that you would need a cable with a 1/4" stereo plug on one side (same plug as on pro headphones) and a pair of RCA or XLR connectors on the other side, to connect to the amplifier. Plug in the cable and DACport becomes a high-quality USB DAC, making it possible to use it as part of a home computer audio setup. In this case we recommend turning DACport’s volume knob to the max and using external amplifier’s controls to adjust the volume (this is the best way to manage gain.) There is no danger in setting DACport’s volume level to maximum – the internal amplifier has plenty of headroom and is guaranteed to never overload, even during the loudest musical passages.

Happy Listening!

Michael Goodman, Chief Product Architect

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