AD724 is it compatible with PC Engine or not?

[grahf]

I was specifically looking at the neobitz DIY kit, since its fairly cheap. Im liking the kit idea, since its time consuming to source all the components seperatly. My question is whether or not anyone has had sucess with the AD724 on pc engine hardware.

From reading on the forums, ive gathered that the AD724 requires a stronger input than the hudson chip produces (while the CXA1645 likes the weaker input). Does this sound about right? If that is correct, will the AD724 work if i build an RGB amp?

EDIT: I should have mentioned, im interested in s-video output from the PCE.

Thanks in advance for any advice.
-Ben

[NFG]

I have an old JROK encoder which I believe uses an AD part.  JROK's really stupid about protecting his ideas, and he won't say for sure what's in there, but I can tell you it definitely doesn't work with the PCE/TG.  All I get is a green screen at best.

The PAL TG-16 uses a CXA1645 to create PAL video, and it's not amplified before it gets to the chip, so we can be assured this works.

[viletim!]

The AD724/5 require .7Vpp (standard) and the CXAs all need about 1Vpp (non-standard). Since the PC Engine doesn't output RGB normaly (or does it? I've never seen one before.), you're grabbing the output from the video DAC? If it feeds a CXA directly then the AD should be fine with some minor attenation on the input.

Generally speaking, you can just slap an AD encoder circuit onto any standard (and that means more than 'I get a picture when I connect my monitor') RGB output and it'll work ok.

[Segasonicfan]

Generally speaking, you can just slap an AD encoder circuit onto any standard (and that means more than 'I get a picture when I connect my monitor') RGB output and it'll work ok.

I dunno about that...the AD chips don't work with a LOT of stuff as I have found the hard way and people that work with the chip a lot to build superguns.  It won't work with a Genesis and most arcade boards so I wouldn't be suprised at all if it didn't work with a TG-16.  In fact, I've heard from elsewhere that it doesn't.

The CXA1645 is your best bet.

-Segasonicfan

[grahf]

Thanks everyone for the info. Im still new to all this, but i find it very interesting so im trying to educate myself. Where can i find more information about "Vpp" (..AD requires .7Vpp, CXA1645 requires 1Vpp..).  I work with surface mount stuff for a living, but my knowledge is very limited outside of what i do.  

[viletim!]

grahf,
Vpp (Volts peak to peak) is a measurement of an AC waveform (or the AC part of an AC waveform with a DC offset). It's used for waveforms that contain changing information that measures from the top of the wave to the bottom (with an oscilloscope ususaly). Other ways to measure AC are Vp (volts peak, half of Vpp) and RMS (Vp * .707) which is used for repetitious waveforms (where power output is more important) like the 50hz mains.

Segasonicfan,
In what way does the AD72x not work? The CXA1645 really needs 1Vpp at it's inputs to make good video so you'd have to either build an amplifier for it or dodgy it by changing the value of the termination resistor (not always predictable).

[Guest]

viletim, I understand what you're saying and the CXA1645 may need a preamp, but the AD724 may not work at all.  I don't think it has anything to do with Vpp, I've talked with people who (as I do) work with these chips a lot, and the AD724/5 just has a MUCH lower compatibility rate.  People that make superguns whom I've talked to (like D-Lite) have to know which chips are the most compatible for all the different arcae boards out there.  The AD chips just aren't up to par, they can't even work with a Genesis signal (colors are way off, sync bounces, etc.)
 

CXA1645 on the other hand works with just about everything according to me and many other people (mostly on the neo-geo.com forums I talk to).  There's a reason it's inside the Neo Geo CD, the Genesis 3, the Saturn, PSX, etc...it's EXTREMELY versatile

-Segasonicfan

[grahf]

viletim!, i appreciate the info on Vpp. Makes sense to me now. I decided to just pick up a CXA1645M (someone is selling a lot on ebay. I offered them $14 and they took it). I think in my case its better for me to just make my own converter, since i want to learn. Even it if turns out more expensive in the end.