High quality hi-res: Amsek Color II RGB monitor. (evaluation) James L. Hockenhull.
High Quality Hi-Res
Many computer users have been attracted to the Apple II because of its ability to produce color video graphics. Those users whose visual ambitions go somewhat beyond zapping the Klingons will probably be interested in obtaining the best possible display of Apple video.
An off-the-shelf Apple can produce images on two types of hardware: regular television sets through a radiofrequency (RF) modulator, and monitors fed by the composite video signal available at the Video Out jack.
The first of these is adequate for home entertainment, but the RF modulator, being in essence a tiny TV transmitting station, is subject to all manner of interference, causing jitter, ghosting, and general degradation of the image.
A video monitor, gives a much more stable picture as the computer signal is piped directly into the circuitry of the monitor. However, image quality is highly dependent upon the quality of the monitor and its ability to make sense out of the Apple video signal which deviates significantly from the standards with which a monitor is designed to work.
The best monitors can give quite a good picture; the worst are hardly better than television sets. Some will not accept the Apple video signal at all.
Top-quality professional graphics devices, those used with mini and mainframe computers, do not use a composite video signal. Rather they work with three separate signals, one for each of the color guns in the display tube--red, green, and blue, hence the acronym RGB. The Amdek Corporation (formerly Leedex) of Arlington Heights, IL has made this professional display technology available to Apple II users with their Digital Video Multiplexor (DVM) and Color II RGB monitor.
Digital Video Multiplexor (DVM)
The DVM, which retails for $199, is the heart of the Amdek system. It picks signals from various parts of the Apple video-generating hardware and puts out red, green, and blue signals along with separate horizontal and vertical timing pulses. Timing information is critical to image quality; that produced by the DVM appears to be much closer to industry standards than that produced by the Apple.
The main printed circuit board of the DVM is a large one. Eleven inches long, it extends well toward the front of the computer case, with its top front corner cut off to clear the case cover. The board carries 37 integrated circuits (ICs) mounted in sockets.
In addition there are two satellite "daughterboards' which fit between certain of the Apple ICs and the motherboard. A cable connects the daughterboards to the main DVM card. A second cable supplies output to a 9-pin D-type connector but also makes a branch to pick up 40-column text input from pin 2 of the Molex connector at location K-14 of the motherboard. Obviously the production of well-timed RGB output is not a trivial matter.
Three channels of the DVM supply red, green, and blue signals. A fourth channel is provided for use with an 80-column text board.
The Color II high-resolution monitor superficially resembles a nicely-designed 13 color television set. Its beige and black plastic case measures 16 7/8 X 14 1/2 X 15 , and its feet are spaced so that it will just fit on top of the Apple case. It retails for $899.
A look at the controls makes it apparent that the Color II is not just another TV: on-off, contrast, brightness, and vertical hold. Period. There is no volume (there is no speaker), no color, no tint, and, of course, no channel selector. This is a specialized machine.
The documentation supplied with the Color II is "consumer oriented,' disappointingly so, in my opinion, considering the professional quality of the monitor itself. Seven of the eleven pages in the booklet are taken up with such matters as location of controls (since there are only five controls, this is not too complicated), how to turn the set on (ditto), and several pages of precautions, with little cartoon figures beset by sweat-beads, X's, and exclamation points illustrating such warnings as "Do not hold anything by the power cord' and "Do not apply a shock by dropping, crushing, etc.' I mention this simply because I believe that those who purchase expensive, professional-quality equipment expect, deserve, and need professional-quality documentation.
The last four pages get down to facts, describing the signals required by the Color II, giving a pin-out of the input connector, and offering diagnostics in case the input signal is not correct.
Input is through a standard Type-I 8-pin video connector which expects red video, green video, blue video, horizontal sync, vertical sync, and ground--exactly the signals produced by the DVM board.
Installation and Setup
Installation of the DVM involves more than simply dropping the card into a peripheral slot; integrated circuits must be removed from the motherboard and inserted into sockets on the daughterboards which, in turn, must be inserted into the motherboard. One who has never handled ICs would be well advised not to learn by practicing on the computer.
On the other hand, anyone with even a small amount of experience should have no trouble with the installation, although the price of an IC puller and inserter should be figured into the total cost.
Having issued these warnings, I will say that installation is straightforward and shouldn't take much more than twenty minutes.
The manual includes instructions for connecting to a Videx Videoterm 80-column text card, requiring the soldering of three male Molex pins to the Videoterm. These pins were not included with my evaluation unit, nor was the connecting cable fitted with the necessary female connectors. With nothing more to go on than the blurred photographs and skimpy pinout information in the preliminary manual, I would have to forego the Videoterm connection, although Amdek assures me that the results are spectacular.
Use and Evaluation
The Color II/DVM is transparent to the user; that is, nothing special or different needs to be done when the system is in use, with two exceptions. First, the manual recommends that, when in the hi-res mode, plots should not be made to the coordinates at the extremes of the screen--X coordinates 0 and 279, Y coordinates 0 and 159 (mixed mode) or 191 (full screen mode). When references are made to these coordinates odd "artifacts' may appear on the screen. This means that the graphics display area is reduced slightly and that minor modifications may have to be made in existing programs.
Second, the three color channels are software selectable. Any or all of the guns can be turned on or off by accessing the appropriate memory locations, in much the same way that Apple screen modes are selected.
Shutting off a color gun will, of course, have a pronounced effect on a graphic image, but if the red and blue channels are defeated, the Color II becomes, in effect, a green-phosphor monitor which is wonderfully easy on the eyes for text work. (An extensible language, Forth, for example, allows commands such as GREEN and COLOR to be added to the language system to take full advantage of this capability.)
The first thing I noticed when I brought up the Amdek system was its silence. I spend a lot of time in front of cathode ray tubes (CRTs) and I'm often made uncomforable by the high-pitched whine so characteristic of TVs and monitors. The Color II is silent.
Silence is golden, but graphics is where the virtues of the Color II/ DVM really become apparent. The flicker or twitch or crawl or herringbone but sits there rock-steady like bone but sits there rock-steady like the image on a mainframe terminal. If noise should appear it can usually be eliminated by adjusting a trim pot on the DVM board.
And, oh, the color! I have seen my graphics work on everything from discount house television sets to studio monitors, but I have never seen anything like the Color II/DVM system. The colors are deep and rich; the blue is that blue usually obtained only by oversaturating a regular monitor, the orange is very close to red. Yet when switching back to the text mode there are no color fringes around the characters.
However, least we think we're in heaven, of the 15 lo-res colors, only black, red, green, yellow, magenta, cyan, and white are available. (See Figures 2 and 3.)
The screen image is not only stable and colorful but has extremely sharp resolution and focus, a good thing since the manual gives no hints as to how focus or convergence may be adjusted.
I am a computer artist (for want of a better term). I make my work portable through photographic reproductions, usually 35-mm color slides shot from a video screen. It was natural, then, to test the Color II by shooting a group of slides for comparison with those taken from other devices. The slides show, rather dramatically, the superior clarity and resolution of the Amdek when compared to identical pictures from a high quality composite video monitor of the same screen size. Of course there is absolutely no contest between the Color II and a standard television receiver. (See Figures 3-8.)
It would be nice to report that I preferred the Amdek slides in all cases, but occasionally their clarity was outweighed by the broader range of colors available on composite video monitors. The Color II slides also showed noticeable "barrel distortion' --all four sides of the image being markedly convex. This surprised me as the actual screen image appears to be quite rectilinear. The distortion may be due to some optical effect between screen and camera or it may be that the squareness of the Color II is more psychological than actual. (Some amount of distortion is unavoidable when shooting from any CRT.) These complaints notwithstanding, the slides from the Color II were excellent.
Someday, perhaps, a perfect product will be made, one about which nothing negative can be said. To the best of myd knowledge, that day has not arrived. I do have a few other minor grouses about the Amdek system which I shall now list in no particular order.
My eyes find that 13 screen too large for comfort when the Color II is sitting on top of the Apple. I have had to move the unit to the table behind the computer where it serves very well.
The Color II does not provide a way to kill the color for black and white work. Because of the unusual Apple color structure, a white rectangle may have one green side and one violet. Put another way, the accuracy of the Color II points up the oddities of Apple color video output. Sometimes this can be annoying.
The output connector of the DVM does not fit neatly in any of the access slots at the rear of the Apple; it simply hangs out at the end of its cable. This may seem like a minor matter, but it is a jarring bit of inelegance in a welldesigned system.
And, of course, expense must rear its ugly head. The Color II/DVM combination is not cheap, listing for just about what a bare-bones computer costs. For what market is the system targeted? Amdek estimates that from 10% to 15% of all Apple users are involved in serious graphics applications and will be potential customers. Doubtless, others will be able to afford the best for their more recreational pursuits.
Having voiced the preceding complaints, I shall conclude by saying simply that it doesn't get any better than this. If the don't like Apple graphics on the Amdek Color II/ DVM system the chances are that you won't like Apple graphics anywhere. Both devices are well conceived, free of frills, and meet or surpass their advertised claims. I recommend them highly to those who want the finest in display devices.
Photo: Figure 1. The Amdek Digital Video Multiplexor (DVM) board (foreground) for the Apple II, and the Color II 13' red-green-blue (RGB) monitor.
Photo: Figure 2. The full range of the Apple lo-res colors as displayed on a composite video monitor.
Photo: Figure 3. The Apple lo-res colors as they appear on the Amdek Color II red-green-blue (RGB) monitor. Colors are limited to black, red, green, yellow, magenta, cyan, and white. The Amdek text is clear and free from color fringes.
Photo: Figure 4. A familiar Apple hi-res image, shown on the Amdek Color II monitor, driven by the DVM board.
Photo: Figure 5. The image as it appears on a high quality video monitor.
Photo: Figure 6. The same picture on a television receiver, driven by a popular radio frequency (RF) modulator.
Photo: Figure 7. A close-up of the Amdek image.
Photo: Figure 8. A close-up of the video monitor image.
Photo: Figure 9. A close-up of the TV image. Notice the dramatic differences in resolution.
Products: Amdek Color II RGB Monitor (video display module)