REVIEW: Ambery RGB to VGA Converter/Scaler - Perfect for use with vga monitors

[TheRogue]

     Hey everyone! I thought I should review this product because it solves a problem that many of us X68000 enthusiasts encounter: 15KHz video.  It's not a problem those using an original Sharp monitor have to face. However for those of us (like me, my CZ-608D was damaged in shipping and is off being repaired, so I'm stuck using my LCD panel) using a VGA monitor, there are a fair few games that are rendered difficult (navigating menus blindly looking for the frequency option) or impossible (no way to change to 31KHz) to play.  There are a few well-known scandoublers out there such as the XRGB, but these are difficult to find, hideously expensive when they do come around, and according to many if you get the wrong model you are in for very inferior picture quality. I have a small story about how I found a solution to this problem.

     I collect classic computers. I have since I was 4 years old and my dad dug out his old Commodore 64 from the garage for me to play with. I have been working with a few people and organizations in my city to put together a classic computer museum where everyone can go and experience these amazing machines for themselves. One of the problems I have had to overcome in this hobby is 15KHz RGB video from many many classic computers. One day along the line, I got a complete Atari ST. The computer itself didn't work, but the monitor did (minus a high-pitched squealing noise. A few months later I got an Apple IIGS. It was just the computer, nothing else, no monitor or keyboard or anything, just the computer. I had to hack together a cable to use the Atari ST monitor for my GS. This worked and all was well till the Atari monitor died a sad death. Once again I was left with no display for a few of my beloved computers. I went web-crawling and with a little digging found the product I will review today for sale. People said good things about it, others bad things.  I decided to gamble and get it. It was 100% worth my money.

     This converter just works beautifully with the X68000. For certain computers this converter will not work well, such as (in my experience anyway) the Panasonic FSA1-ST MSX Turbo R.  On others, such as the Apple IIGS and X68000 it works beautifully!. Not only does the converter output a crisp, clear 31KHz signal, it also scales the video to 3 selectable resolutions. The website offering this converter claims that it converts CGA to VGA, however this is incorrect. This converter does not handle digital RGB (CGA) but rather 15KHz Analog RGB, the kind that we need. In addition, this converter will also convert component (YPbPr) video (PAL or NTSC) to VGA. Unfortunately hi-def component video is not supported, but the same company sells a different converter supporting hi-def component to VGA if that's what you need.

     The box is so easy to use, just plug in your X68000 VGA Cable to the input (the box uses an HD-15 D-Sub connector with standard VGA pinout for it's input) , plug in your monitor to the output, connect the included AC adapter, and you are good to go. Sometimes when the box is powered on it will start in Component mode, if that's the case, just push the button (there's only one) on the top of the box to toggle to RGB mode. You will know if you are in component mode, as the picture will be clear and stable, but brightly tinted pink/purple. There is also a switch on the side of the box to select 640x480, 1024x768, or 1366x768. Some software looks better in one resolution as opposed to another, just experiment to find the settings that work best.

  The only negative I have found with this product is in one or two games, certain fast moving objects appear to be made up of vertical lines, however the object is still visible as what it is supposed to be, so it's not a deal breaker for me at least.

All in all, I would very much recommend this product to anyone using a VGA only display with their X68000. I know it makes all the difference for me

More information and link to the Ambery online store where you can purchase this excellent item can be found here: http://www.ambery.com/rgbcgatovgac.html

[Midori]

The thing I dislike about these converters is the fact that they scale the image to another resolution, rather than double them. They should be perfect for a game or similar that outputs 320x240 pixels. Since that will scale nicely to 640x480. But on the X68K we have for example Capcoms Arcade Ports which run in the resolution 384x224. That means not all pixels will be resampled in the horisontal row and a few lines will be resampled twice in the vertical row. If the device interpolates och filters the signal in some way this will be less noticable but will give less sharpness to the image.

For 92$ that is an issue for me. Perhaps more because 15 KHz RGB monitors are widely available over here.

Shouldn't it be possible to make an analogue line doubler instead which just doubles the amount of lines? Simply put that is. In my glorified vision of the subject that should work fine since it is an analouge signal. If it was digital things would likely be different.

[TheRogue]

When it scales the image to a higher res there isn't data loss as if for example you are scaling to 640x480 and the image is not 320x240, it will not be forced to fill the screen. Rather, black bars will be introduced on the left and right or top and bottom of the image to fill the image out to the proper resolution. Just like when watching a4:3 film on a 16:9 display or a 16:9 film on a 4:3 display. I was concerned about this myself when I bought this converter and was pleasantly surprised with the results.

EDIT: And BTW, it is a lot harder then just doubling the lines to convert 15KHz signals to 31KHz signals. The issue is not the resolution, but the frequency of the sync signal. Also, I have found 2 other converters online that I will be ordering to test. They look amazing. They even support 24KHz. I'll let you guys know how they work out.

[Midori]

I'm confused now. The scaled image will be pillarboxer or letterboxed if the source doesn't match a horisontal resolution of 320 or a vertical one of 240?

I'll give two examples to explain my query:

Here are screenshots from two games, Thunder Zone and Cadillacs and Dinosaurs.




Thunder Zone runs at 320x240 while Cadillacs And Dinosaurs(dino from now on) run at 384x224. Thunderzone can be perfectly scaled to 640x480. But Dino can't, the vertical resolution can be doubled without problems, since 224x2 is 448 which is less than 480, although borders will be added.

But, the horisontal resolution doubled will be 768, to much for a 640 limit. So those pixels will simply not be doubled and black borders will appear on the sides instead? Is that how you mean? I made to scaled images to 640x480 to show what I mean.

Thunder Zone will look very good scaled:


Dino will have borders over, under and on the sides of the image when scaled:


And yes, I do realize that doubling lines is probably more work than I can imagine. I simply did some simple math in my head.

Standard Resolution is about 15 Khz, or around 15,75 Khz even. On a 60 Hz monitor that will be beacuse:

60 Hz times about 262 lines equals 15750 Hz, or 15,75 Khz.

So if the lines were doubled, and became 524 instead, then it would become: 524 x 60 = 31440 or 31,4 Khz.

Although the reality is probably far from that easy, or else my searching for make own line doublers probably would wield more results :-)

[TheRogue]

I mean that lets say you have an image that cannot be scaled cleanly up to 640x480 right, the image will be scaled as close to 640x480 as possible without cutting any of the image off or changing the aspect ration, and the remaining space will be filled with black borders. So for example the image may not be scaled 2x, it might only be scaled 1.5x or 1.7x (however much it takes to bring the horizontal rez as close as possible to 640 without going over) and the remaining space (in this case on the top and bottom of the image) will be filled with black borders. Make sense now?

[Midori]

Oh, yes. Now I understand.

I thought it sounded a bit too good :-) Shame I don't have the money to spare to test one myself.

[TheRogue]

What do you mean too good lol? What I described is better then what you described . There's another one for $50.00 that sounds even better if you want to test that one. I'll PM the link to you if you want. I don't want to post it here till I can test it myself so if it's terrible people will be spared a terrible product.

[Midori]

In my opinion it isn't :-)

What you tell me is that the image will be scaled. What I want is simply that pixels should be doubled, and only be doubled if all the pixels can be doubled. If it did that and left me with a screen with borders then I could manually stretch the image to fit with the screens own controlls.

Although, sorry if this feels like repeating. But I don't think that Cadillacs And Dinosaurs would have black borders. Even if the resolution may look like widescreen it still is a 4:3 aspect ratio game. When displayed on a monitor it won't have any borders around the picture. So when scaled through your scaler the output should probably look like this instead:



Which simply ain't what I want. It is blurred, my idea of line doubling would produce an image just as sharp as when viewed on a 15 Khz monitor. Well the image would of course appear sharper because of the different dotpitch but that's not an issue for me.

[TheRogue]

I'm going to try C&D right now and see how it turns out. How about that?  I'll post pics of the result.

EDIT: This may take longer then I thought to work it out. I need to get 15KHz output from my PC working and my 15KHz graphics card hasn't arrived yet. I don't own a C&D CPS board so I'm going to have to do 15KHz from MAME once my card arrives.  I'll post results in a few days.

[TheRogue]

I would like to point out as well that C&D is not a 4:3 game. When dividing the horizontal resolution by the vertical resolution when dealing with a 4:3 image, the result will be 1.33 repeating, however 384x224 gives 1.714285 repeating or an aspect ratio of 1.71:1.

[Midori]

Nope, C&D is indeed a 4:3 game. It just doesn't have a 1:1 pixel ratio. The pixels are meant to be displayed in a rectangular mode.

A CRT display doesn't really care about how many pixels there is in a line. It only cares about the amount of lines in the image, then the lines may be however detailed they want to be. Another exampleis  the Amiga display mode with a 640 x 256 resolution(50 Hz), although the DPI of CRTs often make high horisontal resolutions impractical. Note my earlier calculation for 15,75 Khz, only the number of lines and the number of times they should be drawn is important, how detailed they are is not. That's why Capcoms arcade games using a 384x224 resolution will have the same aspect ratio as a Sega Mega Drive game running at a 256x240 resoltion.

All Capcoms arcade games on their CPS1,2 and 3 systems uses a 384x224 resolution and all of them are 4:3 aspect ratio games. Street Fighter 2 for example, have you ever seen a SF2 arcade cabinett with a widescreen monitor? :-)

The X68000 ports or Capcoms arcade games run in the original resolution aswell, 384x224. And they to are displayed in 4:3. So if you have Ghouls'n Ghosts, Strider or Street Fighter 2 for example those are good replacements for running C&D through mame for you.