A Terrific Tube Preamplifier From Korea, And A - Ultra High Fidelity ...

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Most audiophiles, whether recent converts or longtime hobbyists, are familiar with the elements of a stereo music system and how they fit together. The source is connected to the amplifier, the amplifier is connected to the speakers, the footbone is connected to the shinbone, the lipbone is connected to the trombone. However, now that digital music is migrating to computer hard drives, the flow is less obvious. Even audiophiles who are geeky enough to know how to solder may hesitate before tackling a computer system, and even more before figuring out a way to connect one to a high-quality music system. But before we get to the computer itself, let us have a close look at the component that has been the dominant music source since the mid-eighties, the Compact Disc player. Inside the player A single-box player, the sort most familiar today, actually contains an entire chain of components, whose job it is to reproduce music from a Compact Disc. 1) The drive mechanism. This is the device that spins the disc. It includes a movable laser that swings across the CD surface, while a matching photosensor detects changes in brightness, which correspond to the digital data recorded. In fact it isn’t quite so simple, for several reasons. First the data is not in linear form, as it would be on an LP or a tape. If it were, even a minor glitch on the disc could wipe out an important section of the music and cause catastrophic failure (as happened regularly on the very first digital tape recorders). Instead, the data is scattered across the disc, using the Reed-Solomon code. Second, the data 30 ULTRA HIGH FIDELITY Magazine Nuts&Bolts Inside Computer Music by Paul Bergman is not actually recorded in binary form, as a series of 1’s and 0’s. The pits on the surface (actually the ridges, as seen from the other side) are in much more compact analog form. For instance, a ridge may represent, by its length, the number of 0’s that must go by before the next 1. That is an analog value, but it is not an analog of the music, and c a n n o t b e u s e d t o reprod u c e t h e original signal until it is interpreted, and the digital data stream reconstituted. 2) The servo system. This is an electronic control circuit that tells the drive to spin the disc and lets the laser know where to look for the next piece of information. It seems almost miraculous not only that such a system can be built reliably, but that it can be incorporated into inexpensive mass-market devices. 3) The digital-to-analog converter. The DAC is the bridge between the digital and analog worlds. The recovered (actually reconstituted) digital signal is used to reconstruct a version of the original analog signal. It is called “analog” because there is a perfect analogy between the swing in the voltage and the air vibrations of the original sound. In a Red Book CD player, data packets come 44,100 times per second, and use 16 bits (binary digits) to describe the music signal. It is, however, common to “oversample,” to bump the sampling rate up by four or more times, either by repeating the data samples or by interpolating them — creating an in-between data packet. Oversampling avoids the use of a sharp antialiasing filter to prevent audio from colliding with the sampling frequency. 4) Connections. All players in the past two decades have included digital outputs, which allow one to extract the raw digital data and send it to an external DAC. Only recently have some players appeared with digital inputs, allowing the use of the built-in DAC with external sources, such as computers. Of course that is the very subject I wish to discuss in this article. Storing music on a hard drive At one time this was difficult to do, because, as I have explained, the code is stored on a CD in discontinuous form, and one could not simply slide a track from the CD to a hard drive window. If one did, the result would be merely a pointer to the original track, which would work only if the CD were present. Modern operating systems contain algorithms that permit translation of the data into the WAV format that is native to Windows (or AIFF on the Mac), simply by sliding the file onto the hard drive window. There may, however, be better ways to do this. Such transfers do work quite well with normal digital files, and for-
tunately so, because computer software and files are quite intolerant of errors. Recall, however, that the music on a CD is neither in WAV or AIFF form. It may, therefore, be advantageous to use a method which can check the integrity of the data as the transfer is being made. Several programs can do this. Apple’s iTunes, used by anyone who owns an iPod, can be set to do it (in the preferences general pane, choose Import Options, and check using error correction. On a Windows PC, MediaMonkey is also used for the same purpose. There are, however, limits to error correction because of the translation process. If the drive is consistent in its errors, there is no way to get it right, because there is no way to determine that an error actually exists. The same would of course be true if you were playing the CD directly in your player. Whatever method you select, you now have a music file on your hard drive. Potentially it can be very well reproduced, because this time the actual binary digital data is stored, not an analog interpretation of that data. That is possible because the magnetic disc is a far more secure repository of data than a plastic optical disc can ever be. Backing It Up I should hardly need to remind you that data, if it has any value, needs to be copied for safekeeping. Even if you keep all of the original CDs you own, transferring them to hard drive represents a good deal of work, and you will not wish to risk having to replicate the tasks. You will want a second hard drive for a safety copy, and you may want to ponder where you will store it. An extra drive inside or next to the computer may be a good choice, but a fire or a burglary can lead to the loss of both the original drive and its safety copy. Getting music where it needs to go Once your music is on a hard drive, you can play it back on the computer itself. That’s convenient enough if your computer is also your music system, but if you are reading this magazine this is in all likelihood not your case. You will want to send the digital signal where it needs to go. Of course you will need some sort of DAC in order to turn the signal back into analog, so that it can be amplified and reproduced. A number of transmission methods can be used. 1) Firewire. This Apple-invented protocol, also known as IEEE 1394, is now an international standard. In reallife applications Firewire is much faster than USB 2.0, and it will pass not only Red Book data (16-bit/44.1 kHz), but up to 24/192. It is not suited to long runs, however. Though Firewire devices can be daisy-chained, the length limit of any single connecting cable is 4.5 metres. Audiophile DAC’s seldom come with Firewire, though some pro-audio devices do. Yes, it’s interactive Just click on the ad on the next page, and you know what will happen? You’ll go right to the advertiser’s Web site…if there is one, and of course if you are connected to the Internet at that moment. Try it with any of the other ads in this issue. Of course it works with the full (paid) electronic issue as well. 2) USB. It is increasingly common for audiophile DAC’s, amplifiers, preamplifiers and even CD players to have USB connections. Since modern computer all have a USB bus, this is an appealing way of getting from computer to external device. However USB can accept only short runs of 5 metres, barely longer than Firewire. Some commonly-used USB chipsets offer poor performance, and on many (but not all) systems the bandwidth is limited to little more than Red Book CD standard. This limitation is not inherent in the standard, however, and some USB devices will pass 24/96. This is the case of numerous professional input-output boxes I have worked with. 3) Ethernet. This cabling is commonly used for home and business computer networks. It is asynchronous, which means it does not carry clock information, and is theoretically immune to system jitter. The cable itself is inexpensive, and it can be used for very long runs, making it suitable for setups in which the computer is a long way from the music system. Not all devices are designed to use Ethernet, however. The Linn “DS” devices have Ethernet connection, and so do the Logitech Squeezebox products. Apple’s Airport Express is primarily a wireless device, but it does have Ethernet connectivity and can be used that way. 4) Wireless. This generally refers to the use of some sort of Wi-Fi network, which most people with computers already have. There are a number of devices that can connect to your Wi-Fi network, and can receive streamed music from your computer. That includes the already-mentioned Squeezebox and the ULTRA HIGH FIDELITY Magazine 31 Nuts&Bolts Feedback
Page 1 and 2: No. 89 CAN $6.49 / US $7.69 RETURN
Page 3 and 4: Issue No. 89 Cover story: Two of th
Page 5 and 6: I HATE DOG EARS! (SORRY FIDO) We’
Page 7 and 8: I’m looking forward to the Simaud
Page 9 and 10: started talking to me and I was sta
Page 11 and 12: I’m using a Cardas Lightning cabl
Page 13 and 14: Leslie, it’s painful to realize t
Page 15 and 16: music from a computer via Ethernet
Page 17 and 18: school or community centre, perhaps
Page 19 and 20: ut the tone of the warning seems wr
Page 21 and 22: I remember when Israel Blume of Coi
Page 23 and 24: I may have mentioned that there is
Page 25 and 26: Thiel was back at CES, exhibiting a
Page 27 and 28: Touring the Salon there many turnta
Page 29: Below left: the Vivid B-1, designed
Page 33 and 34: The new ASW Genius 110 One of the i
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Page 37 and 38: scene, such as a video game page. T
Page 39 and 40: THE ANNIVERSARY COLLECTION: Issues
Page 41 and 42: Adding it to a CD player There are
Page 43 and 44: output of our Macbook Pro to the 30
Page 45 and 46: a quality switch with an array of f
Page 47 and 48: Leema Elements Phono Preamp Yes, wh
Page 49 and 50: Your System Belongs on the Wall Tar
Page 51 and 52: The t wo woofers and the midrange d
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Page 55 and 56: INTERCONNECTS ATLAS NAVIGATOR Oxyge
Page 57 and 58: UHF14 POWER BAR Most power bars kno
Page 59 and 60: ed pepper to its music. Felix Hell
Page 61 and 62: Mozart: Sinfonia Concertante (XRCD)
Page 63 and 64: Gentlemen, I, Rachmaninoff, have ju
Page 65 and 66: painful scenes at home, and after a
Page 67 and 68: It is worth noting that although th
Page 69 and 70: announcement of impending marriage
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Page 75 and 76: any woman who is not married to som
Page 77 and 78: All You Can Watch for $8 It was Net
Page 79 and 80: The Magic Without 3D What’s domin
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Industry News Dan d’Agostino is b
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