Re: An LCD for your IIGS?

[mjmahon@aol.com (Michael J. Mahon)]

Ed Eastman replied:

>Cofirm this is what I was referring to:
>IIgs --> Mac to VGA adapter --> VGA to component adapter --> Display
>
>After doing some research, looks like the there are multiple definitions 
>of component video these days.  There is the RGB and two mixing schemes 
>similar to Svideo.  The projector I used had component inpuits that 
>accepted RGB and synched down to 15kHz.  The cable was almost a direct 
>feed with wiring and a little impedence matching inductors to ensure 
>good video quality.

So it sounds like you were going RGB-to-RGB.  "Component" video
inputs have not really proliferated until the last few years, with HDTV-
readiness.

>If you want the S-Video type component out, you will need an adapter to 
>mix the signals.  Again, myu set-up was almost strait through.  (Ever 
>play Sobotage on an 8 foot screen?)
>
>Michael J. Mahon wrote:
>> BTW, I have never seen such a VGA-to-component cable.  Where
>> are these obtainable?
>
>For example, you may find one here for $200 here...
>http://www.ramelectronics.net/html/kd-vtca2.htm

Yep, that looks exactly like what I expected--external power for
buffers and a resistive matrix transcoder for RGB to YPrPb.

Note that the output scanning standards are identical to the
input standards, since nothing but analog mixing is done.

This would be fine for the IIgs, since it would deliver NTSC-rate
component signals with high bandwidth to a video monitor/HDTV.

S-Video is quite different, since it has only two signals:  the Y
signal (of potentially high bandwidth) and the quadrature
modulated chrominance subcarrier, which is necessarily
limited to less bandwidth than the subcarrier frequency
(3.58MHz).  S-Video is better than composite (since the
luminance signal will not be bandwidth-limited by separating
out the chrominance subcarrier), but substantially inferior
to RGB or component video (which have no intrinsic chroma
bandwidth limitations).

So this kind of setup ($199 "converter" + adapter) will deliver
all the sharpness of RGB, which should be _great_ for a CRT
display.  Now, the question remaining is how the IIgs's discrete
pixels will be mapped to a discrete pixel display, like an LCD or DLP...

(BTW, such a converter could be built using video op-amps for
less than $10, as you might expect.  In a previous post I gave
a reference to an application note for such a design.  ;-)

-michael

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