This is not a true review, just my initial experience and opinion on this product.
Just got an Ultimarc J-pac I ordered from divemaster. First of all let me say that ordering through him is great. He shipped right away and the shipping price was very good. I have also ordered other items direct from Andy at Ultimarc and he is great too. From what I have seen so far the Ultimarc line of products are top-notch.
The J-Pac is a very handy device for quickly hooking up a PC to a Jamma cab. It is available in a USB and PS/2 variety and has a keyboard pass-through so you can still use a PS/2 keyboard attached to the J-pac (I got the PS/2 version).
The J-pac has a VGA input and a protection circuit that prevents too high of a sync rate from reaching the monitor (it still allows you to see the pc booting up by "splitting" the screen across the middle).
Audio input is handled by a screw down connector so you need to provide your own cable to connect the audio out from your PC to the J-pac.
My test rig is a NeoGeo cabinet with a 25" monitor and an old PC with a 1.4Ghz P3 proc with a Matrox G400 video card. I setup a bootable Advancecd with some horizontal orientation roms and appropriate sound samples for a quick test. I also added the appropriate config files for outputting the correct sync rate.
This is the info for setting up the advancecd config files (advmame.rc and advmenu.rc):http://advancemame.sourceforge.net/doc-advcd.html
You can also use an ArcadeVGA card or programs such as Powerstrip or Soft-15Khz.
My initial impression of this product is great! Plug and play all the way except for the audio, I use a pair of PC speakers for my test but will hook into the built in speakers soon).
The J-pac has the default Mame keyboard mapping already or you can program your own. There is a video amplifier as well to get the voltage up from the vga default of .7volt to 1volt.
as you can see from the pics the video quality is great.
This product is great for a quick Mame cab build. If you can get a basic Jamma cab with a good control panel and monitor you are well on your way to having a Mame cab on the cheap and with the least amount of hassle and aggravation.
I recommend this to any beginning Mame cab builder (like myself!!)
Product info here:http://www.ultimarc.com/jpac.html