If you are interested in audiophile-class music reproduction, you probably already know what type of gadget this is. If not, you may wonder why anybody would use such a thing. At the most fundamental level, all CD (and DVD) players already have digital-to-analog converter (DAC) circuitry built into them. These electronics take the digital pulses read from the CD/DVD and convert them into electrical signals intended to faithfully reproduce the original source music. It's how the 0's and 1's are turned into complex waveforms like you see on an oscilloscope. These signals are then fed to your receiver or amplifier for signal gain and then to your speaker system or headphones. The DAC is a critical step in reproducing digitally recorded sound and, as you might guess, cheaper players use cheaper circuits and components to accomplish the task. In one sense, the recorded material is being "recreated" by the DAC process, just like a phono cartridge on a turntable recreates music from a modulated groove in the vinyl. For all the same reasons, the DAC circuits can be a source of problems: introducing residual noise, limiting dynamic range, creating audio anomalies, or just plain failing to properly convert the digital stream.

Enter the component DAC unit. The Audio Alchemy Ultra DAC is just one of many component DAC's from different manufacturers. (Note: Audio Alchemy is out of business and new units are no longer available.) The Ultra DAC consists of the Ultra DAC itself and a separate power supply unit. The power supply is always on and the Ultra DAC is always under power, in order to keep it stabilized and at operating temperatures. You have to have a CD/DVD player with a digital output to use the Ultra DAC. You connect the PCM (pulse code modulated) digital output signal from your player to the Ultra DAC input. You can use either fiberoptic (TOSLink) or copper cable, but I recommend fiberoptic as it eliminates any electrical connection between the player and the Ultra DAC, reducing the likelihood of hum or noise. You then connect the standard audio outputs (left and right channels) to your amplifier or receiver using high-quality patch cables. The Ultra DAC is actually both a DAC and a "jitter" reduction unit. "Jitter" is imprecision in the timing of the discrete digital samples of the audio signal, either when recording or playing back. The Ultra DAC uses special circuitry to reduce "jitter" and lock on to the digital stream more accurately.

So, why is a DAC/Jitter Reduction unit so valuable? Well, aside from the superior sound it produces (see below), it actually enables you to use really cheap CD/DVD players, as long as they have PCM digital outputs. When you use any DAC, the player becomes just a transport system for the media. As long as you're getting a PCM digital signal from the CD/DVD player, you're going to get audio quality identical to that from any other player with which you use the Ultra DAC. Within the limits of stability and error-correction, a $50 and a $500 CD player will sound exactly the same, since the stream of 0's and 1's are theoretically identical and the Ultra DAC is doing all the critical work.

Now to the performance of the Ultra DAC. In a word, excellent. The frequency range, accuracy, transparency, and dynamics of the Ultra DAC are exemplary. I know that there are better units out there, but I don't have the golden ears to tell the difference between them and the Ultra DAC. I do, however, have the ability to hear the difference between the inexpensive DAC circuitry built into my Sony 5-CD changer and the sound of the Ultra DAC using the Sony's fiberoptic digital output. This is especially noticeable on acoustic guitar, which is far more vibrant and life-like with the Ultra DAC. Of course, if you are using inexpensive speakers or amplifiers, you will not notice the improvement nearly as much. Same with the recorded material itself...poorly recorded material will reproduce as poorly recorded material. The Ultra DAC doesn't work miracles.

So you have your MP3 player and you've converted tons of music tracks to MP3 or OGG format. You've probably also stashed them on your home computer so you can sort, manage, and trade them, as well as enjoying them while you're working. The next logical step is to make them available to your home stereo system. If, like me, you don't keep your computers in the living room, you may end up trying a couple different paths...running audio cable from the computer(s) to the stereo, hooking up your MP3 player to the stereo using a couple adapters, using a wireless audio link, etc. None of these are very satisfactory.

Enter the D-Link DSM series of "Media Lounges". (How the heck did they come up with that name?) The models vary in their features, but I have a DSM-320, which is the basic 802.11g wireless unit that plays audio and video files and allows you to view image files. It is also compatible with several of the streaming audio services, so I can use it to access my Listen Rhapsody account. Since the DSM-320 is video-capable, you don't have to goof around with the tiny LCD displays of some of the other network media players. Everything is nice and big on your TV, display, or monitor.

The DSM-320 is big, but very flat, so it stacks well with your stereo equipment. There is a small wifi antenna at the rear that can be oriented sideways, if required, so the unit will fit in a rack. There are several different types of outputs, including digital audio (copper only), discrete channel audio, RF-modulated video, composite video, and component video. You also have the option of connecting the unit directly to a port on a router or switch for faster data transfer. This is handy if you are going to use it to view video files, since the 802.11g has to really stretch to provide adequate bandwidth for decent video. But it is more than enough bandwidth for good quality audio streaming. When you configure the unit, you must select either wireless or wired service, but you can change this at any time using your remote control.

In order for the DSM-320 to access your media files, you must load the D-Link Media Server (included) application to the computer(s) where the media files reside. The Server will allow you to designate drives or folders as available for media playback and will then scan them to ascertain what files are compatible with the unit. You can schedule the Server to refresh the folder information on a regular basis. New files will not be available until the server has been refreshed. You can also name the folders (and the computer) to make them more easily distinguishable from other shared resources. When the DSM-320 searches your network for Servers, it will display a list of available servers. Unfortunately, it is rather time-consuming and cumbersome to switch between Servers. (There should be a simple single-button operation to scroll between servers.) Once the DSM-320 has been configured (and you have downloaded and installed any firmware upgrades), you can select a variety of ways to access and play your media files...by artist, by album, by playlist, or by folder contents. The track tag information is displayed on the TV while the track plays, as well as showing the next track scheduled for play. You can also skip tracks, engage shuffle play, and perform other management functions. There is one little problem with the arrangement of the tracks, though...they are listed alphabetically by track name when they are in MP3 format. If you compress your audio files in OGG format, they are listed in track sequence (based on the tag information). I understand that this is due to some Windows service, not the D-Link Media Server, but that doesn't make me feel any better. I've had to go through and recompress over 2500 files in order to have them listed and displayed in the proper sequence.

So, how does it sound? Fine. Mine is connected using the discrete audio outputs and I don't notice any audible hum or noise. Of course, don't expect miracles...MP3 files still sound like MP3 files. But track management is a real joy with the great big display on the TV. The 802.11g wireless connection seems to work just fine for MP3 files at any bit-rate. Video files are a bit more of a problem and you may have to fiddle with their bit-rate to get them to play back correctly. Connecting the unit directly to your network through a router or switch usually solves the problem. WMV files are not compatible with the unit, but most AVI files and MPEG-2 files are. XviD-encoded files are handled perfectly, but DivX-encoded files yield varying results. This is sort of a minor issue for me, as I just don't keep a lot of video files on my HDDs. If I want to keep a video, I make it into a DVD and then play it back using a DVD player. Why got to all the trouble to rip videos to accommodate your system's eccentricities?

UPDATE (18 June 2007): I have found that the D-Link Media Server software intended for use with this unit just doesn't cut the mustard. I have had some problems with service availability, slow response, and the need to run the update (refresh) function manually whenever I make minor changes in the media library. It also has some odd ways of organizing the tracks within a folder or album. Since the DSM-320 is UPnP (Universal Plug n Play) compliant, I tried a couple media server applications from other vendors. The one that seems to work best is from TwonkyVision (no, I'm not making that up) and is called TwonkyMedia. It is not a free application, but you can download it and try a full-function demo from their site to see if it works with your media device. TwonkyMedia runs as a service on your file server and is MUCH faster than the D-Link application. It also updates the file library whenever you make a change, so you don't have to schedule it to refresh the library or run a refresh manually. Finally, it seems to do a much better job of organizing the library and track as it provides them to the media device. Highly-recommended.

I think that this was originally intended to be used in a car system. The DITB is a small DAC with both optical and coaxial digital inputs, powered by 12 VDC. I use it mainly with my Little Dot II++ Tube Headphone Amplifier and CyberHome CH-300S CD/DVD Player. If I want to listen to a CD, I use the (very) inexpensive and simple CH-300S as the CD transport and connect the coaxial output to the DITB. This is not as good as using an optical cable, as it doesn't ensure complete electrical isolation of the CD player from the DAC, but it does bypass the (probably inexpensive) amplifier section of the DVD/CD player. I then feed the output from the DITB to the Little Dot amplifier. I find that the sound quality improves dramatically if you power the DITB from a battery. (I use a 4.5AH lead-acid battery and a small charger with an external transformer. I have a switch in the cable from the transformer to the battery charger, which I turn off when using the DITB.) The DC from a battery has no hum or residual noise and eliminates the potential for any ground loops. It also provides significantly more current for the unit than the wall-wart does.

The sound quality is excellent, though not a match for the much more expensive DACs on the market. If I use a wall-wart DC power supply, the noise and hum are noticeable. The construction quality is above-average and I've had no problems with the unit's operation. To be honest, this set-up was my solution to the problem of compression artifacts in my compressed digital media. I needed to be able to play CDs next to my recliner...which meant I had to connect a CD player to my Little Dot amplifier...which meant I needed to separate the CD player electrically from the amplifier...which meant I needed to have some way to convert the optical S/PDIF output to an analog signal as transparently as possible. Anyway, you get the idea.

I have found that this unit works pretty well with the Turtle Beach Audio Advantage USB Sound device, which has an optical output through a combination headphone/TOSLINK connector. They synch up just fine and the result is very quiet. You can get one of these DACs and an AA for less than $90. An optical cable even comes with the DAC.

Another little gadget that you may not even know exists. Let's say that you have a desktop or laptop computer and that you want to use it to listen to digital files, CDs, or DVDs. If you're already interested in good quality sound, you've probably upgraded your desktop to a higher-quality internal sound card and disabled the motherboard audio chipset. If you have a laptop, this option is closed to you, but you may have purchased an exterior USB sound card to improve your listening. The problem with using the stock (OEM) audio cards/chipsets is that they're usually not of the highest quality and they have a tendency to (1) be underpowered, and (2) pick up noise from internal or external sources. In many cases, the feature sets of internal chipsets are quite limited. So, what do we do?

This is a variation on an old idea. It's an RF modulator that converts stereo audio and NTSC composite video into UHF broadcast frequencies so they can be viewed on TVs with UHF tuners. This unit can also broadcast the RF signals at low power so you don't even need to connect the antenna output of the unit to the antenna input of the TV. Unlike many video/audio RF modulators and VCRs, this unit does not operate on VHF channels 3 or 4. There is a recessed tuning adjustment on the front of the unit that allows you to adjust it between about UHF channels 16 and 30. A sliding switch selects whether you RF modulate the signal for direct connection to the TV or whether you broadcast on the attached antenna. There is also a volume control on the back that is very useful in adjusting the level of the video signal to match the audio level of other sources on your TV.

The unit works as advertised and I have no problem at all watching sports events rebroadcast from my satellite dish while sitting on the back deck with a portable TV. In fact, it works so well that I'm fairly convinced that it broadcasts at power levels that may be illegal under FCC rules. One thing is for certain...there are no FCC labels or UL labels anywhere on this unit or on the box it came in.

Which brings us to one near-catastrophe I had when I first received the unit. I opened the box, connected it to my equipment, and then plugged it in and turned it on. Nothing happened. Furthermore, there was a rattling sound when I moved the unit. After trying everything I could thing of, I finally unplugged it and opened the top of the case. I found that the power cord came through a strain relief and was supposed to connect to the primary leads of a power transformer. The connection was made with wire nuts and these had come off and were rattling around in the bottom of the case. This meant that the 120 VAC power cord conductors were exposed and nearly touching the metal case itself. I would have been quite surprised if they had actually touched the case while I was holding it. I quickly repaired the connections and taped them. It's worked just great ever since.

You may not know that these even exist, much less have thought you might actually use one. This is a networked video server that takes video and audio inputs from a cable box, satellite receiver, DVD player, or just about any other video source and streams them to your LAN or WAN. But it also does a lot more. It allows you to remotely send signals to control your equipment using the IR transmitters plugged into the unit. This means you can sit on your deck with your WiFi laptop and watch your cable or satellite programming on the screen, changing channels and adjusting your equipment with pop-up virtual controls that actually look like your normal remote(s). It also works well across the Internet, giving you the ability to watch programming or DVDs from a hotel room, a friend's house, or from work. The SlingBox has a lot of features and can be complex (though not necessarily) to setup and use properly.

Accepting S-video, composite, or antenna inputs, the SlingBox is normally inserted between the video/audio source and the display unit (usually a TV). You place one or both of the IR transmitters that are wired to the unit in front of the device you want to control. There's a standard RJ-45 TCP/IP network connection on the back. (Although you can use the unit without a hardwired network, you must buy a WiFi "bridge" or "gaming adapter" if you don't have a hardwired connection from your LAN to the unit's location. There are no WiFi capabilities built into the unit.)

You then load the SlingBox suite on your PC. Using the setup utility (and your WiFi management tools, if going this route), you locate the SlingBox on the LAN and configure it. This can be a bit daunting, but the default settings generally work well. I had no problems at all, but the SlingBox forums are full of people who need some help. You also have the option of registering the unit with a SlingBox-sponsored server that allows you to locate the unit from remote sites across the Internet. (This is not necessary if you're fortunate enough to have a fixed IP address from your ISP.) Bandwidth, video quality, and other settings are all user-adjustable over a very wide range. The SlingBox will then compress your video/audio at the desired rate and transmit it to a viewing utility, called SlingPlayer, you run on your PC.

My unit works great and the video/audio is very acceptable, though not up to par with, say, a DVD or good VHS tape. The unit can be a bandwidth hog at high resolution, but this is usually not a concern at home. However, IS managers at your workplace will probably frown on your using this on their WAN, even at fairly low resolution and quality.

In order to prevent video piracy and reduce the likelihood of DVD and videocassette duplication, the studios use several different copy-protection schemes. On of the more popular is Macrovision, which comes in several different "flavors" and generations. If you have a DVD or videocassette that you are trying to duplicate or convert, and you get a resultant picture that shifts slowly from B&W to color and back again, you are trying to copy a Macrovision-protected source. You may also see some picture instability. The Sima CopyMaster uses some simple circuitry to stabilize the video signal and eliminate the problem. It doesn't work with all copy-protected sources, but it works with an awful lot of them.

Operation is pretty simple. You just feed the composite video signal through the unit (an S-video connection is also provided) and then turn it on. A sliding scale of LEDs will show the video level and tell you it's processing video. You can also move a slider switch and convert the signal to B&W. I guess this is so you can avoid the whole issue, if you're willing to watch a color movie in B&W. The unit uses a wall-bud power supply and does not operate on batteries.

There are a couple good reasons to have one of these. First, this is a great way to improve the audio quality of your laptop, due to its low noise, high fidelity, and increased power output to your headphones. The other great use for this is when you have a laptop with a sound card/chipset that has "gone South" on you. The sound card on my HP laptop just died about three years ago. Plug one of these babies into the USB port, though, and you're ready to go again.

If you want to be a bit more sophisticated, you can use the optical S/PDIF output on the AA Micro. The unit comes with a TOSLINK (optical) cable adapter that plugs into the headphone jack, allowing you to feed an optical signal to an external DAC or any device that will accept an optical input and decode it properly. I use mine with my DITB (above) and get great results. The advantage is not only that you're getting the "raw" digital signal from the CD/DVD/music file, unhampered by the electronics of the laptop, but you're also eliminating the electrical problems that often arise when you connect a piece of electrical equipment to a laptop. There's no hum and no possibility of noise or ground loops.

There are a couple minor issues with the AA Micro. One thing that irritates me is that you usually have to reinstall the driver when you switch the device to another USB port. Fortunately, this only takes a moment, but it can be aggravating when you realize that you have something else plugged into the port you normally use for the AA Micro. Also, the management application for the unit is fairly complex and permits you to do all sorts of things that might appeal to gamers, but are absolutely useless to me. I just want the unit to feed stereo signals to my headphones or to an external DAC...that's it.

Video scalers are not that unusual. They are frequently used for home theater installations and for business presentations. The Video Scaler Pro is a powerful, but fairly simple, unit that can be used in several different ways. It is most often used to convert video signals of one type to video output of another. For example, you can convert NTSC (North American) format video signals to PAL (Europe and some other countries) format. Or you can convert VGA outputs from computers into composite video to feed a standard video monitor or TV. The Video Scaler Pro will automatically detect the type of video signal it is receiving and then let you select the type of signal you want it converted to. In order to do this, the unit has to "disassemble" the video signal and then "reassemble" it with proper timing and signal levels. This is the key to why it is so handy. When a video signal is processed in this way, which includes applying time-base correction to the scan lines, virtually all copy-protection schemes prove useless. In many cases, you also get significant improvement in the quality of the video, especially if it was recorded on an older videocassette.

The Video Scaler Pro comes with everything you need and is relatively easy to hook-up. There aren't really any adjustments to make, though you can select the resolution of the output video signal. I have a VCR that has a time-base correction circuit built into it, but the Video Scaler Pro does a better job of processing the video from older tapes. VideoLabs, the manufacturer, is now ClearOne.

Description.