connecting the CPC to a VGA monitor

[Tied]

Well, I know that the big problem to achieve this is to separate the
composite sync to a separate Hsync and Vsync, I heard about a circuit
(the tv's do something like this) that can do this...

If we achieve this (separate de syncs), can a VGA monitor be connected
to a cpc? or is totally impossible?

Someone knows the circuit I'm talking about?

Regards

[Andreas Micklei]

You mean a sync-stripper. They are very common in the home-cinema-scene
because many video beamers can handle an RGB video signal but need
separate H-Sync and V-Sync. People therefore use sync-strippers to
connect the SCART output of their DVD-Players or Settop-boxes to their
video beamers.

Unfortunately a PAL video signal has a line frequency of 15kHz while VGA
uses a line frequency of 30kHz. Home-cinema beamers can usually handle
15kHz (that's what they are made for), but only very old Multiscan
monitors can also handle 15kHz (the Commodore 1942 for example). For a
more modern monitor you will need a scandoubler which doubles every
line, converting the 15kHz signal into a 30kHz signal. You can buy boxes
with sync-stripper and scandoubler combined. People use them for
connecting games consoles to their Computer monitors.

This box for example might work:
http://www.lik-sang.com/info.php?category=219&products_id=2875&PHPSESSID=0d6d3a81f92d4fa3799f3b940bd40ea2
http://www.tiptonium.com/videogames/reviews/other/XRGB2-PLUS.htm

For Amiga you could for example use this (I don't know how easy Amiga
stuff can be converted to CPC. It is probabyl possible):
http://www.mmd-shop.de/ext_ff.htm

There are probably others, and there are circuit diagrams to build your
own sync-stripper if your monitor can handle 15kHz.

bye...
Andreas Micklei

[Tied]

mmmm it seems very very hard to build one sync-stripper-doubler with a
schematic and pcb... And the price for the commercial version... 176$
is so much for me!!

the question is... the image of an cpc will be best displayed in a
VGA/SVGA monitor? how?

converting the 15khz to a 30khz signal... will change in any way the
look of the cpc screen? will it operate more than 50hz of refresh?

Regards

[Andreas Micklei]

Hi,

Tied <sjos...@hotmail.com> wrote:
> mmmm it seems very very hard to build one sync-stripper-doubler with a
> schematic and pcb... And the price for the commercial version... 176$
> is so much for me!!

Thats's actually cheap. Video processors from the home cinema world
which do similar things (plus possibly a bit more, like adaptive
interlacing, smooth scaling, etc) cost ten times the price. :-(

I also know the scan-doubler thingies from the Amiga world (Amiga was my
second computer after CPC). They have always been expensive.

> the question is... the image of an cpc will be best displayed in a
> VGA/SVGA monitor? how?

> converting the 15khz to a 30khz signal... will change in any way the
> look of the cpc screen? will it operate more than 50hz of refresh?

If you use a line-doubler that can handle PAL the picture will be
identical in theory. In practice you will get a much crisper picture,
which is nice for doing text processing in mode 2 for example. However
games may actually look worse, since the CPC has only very low
resolution modes by todays standards. On a crisp modern monitor you can
see the actual pixels much more cleary. It gets worse if you use a
bigger monitor. Also modern PC Monitors are not really up to a picture
frequency of 50 Hz. They are constructed for 70 Hz and up, so when you
feed it a 50 Hz picture you will notice much more flicker than on an
original CPC monitor or a television for example.

So much for VGA upscan converters and the like. I never actually used
one, but they sure look nice. However here are some alternative
solutions I have tried:

- Get an MP-2 Modulator (or build your own DIY version from the
schematic on Kevin Thackers website) and feed the composite signal to
a TV-Card or the video in of your Graphics-Card.
Pro: Cheap, easy, CPC-in-a-window-wow-effect
Contra: Bad picture quality

- Build a SCART lead and use a TV set instead of a Monitor.
Pro: Nice picture (depending on the TV set), very easy
Contra: It's not a monitor

- Don't use a CPC at all. Use an emulator instead.
Pro: Zero cost, zero effort, works instantly
Contra: Needs a fast PC for accurate emulation, it's not the real
thing (tm)

Having said that I would go the emulator route if you really want to run
CPC software on your PC monitor. A CPC without the genuine original
monitor is not the real thing anyway, or is it? ;-)

bye...
Andreas Micklei