The dbGrafx Booster is an audio video enhancer for the PC Engine and Turbografx-16 consoles. It uses a Sony CXA1645 video encoder to amplify RGB and transcodes CVBS and S-Video from the RGB to produce multiple video outputs.
The RGB video is driven directly by the CXA1645 and output on the Mini-DIN 9 (Genesis 2) connector. It is intended to interface two types of cable:
- Compatible Genesis 2 SCART cable including coupling capacitors (220uF minimum) installed in the SCART head and 75 ohm resistors installed in the Mini-DIN head
- HDRetrovision Genesis component cable – I know it’s not RGB but the signal quality is equally amazing
SCART cables which do not contain both the appropriate resistors and capacitors on the RGB lines are supported and should not be used with the Grafxbooster (or your Genesis 2 console for that matter). Also, SCART cables containing “CSYNC boosters” (example shown below) or other non-sense features claiming to reduce or remove jailbars are not recommended and should also not be used.
The S-Video signals are driven by the CXA1645 and output on a standard Mini-DIN 4 connector. It is intended to interface to standard S-Video cables.
There are two distinct CVBS outputs on the Grafxbooster. One is output on the yellow RCA jack and is intended to interface to standard RCA cable. The other is output on the Mini-DIN 9 (Genesis 2) connector and is intended to interface to a Genesis 2 A/V cable.
The CSYNC signal output on the Mini-DIN 9 (Genesis 2) connector is conditioned directly from the console’s CSYNC signal – it is not decoded by an LM1881 from the composite video signal. The CSYNC output voltage is selectable via jumper on the board. The two possible settings are:
- The CSYNC voltage output is approximately 600mV and its output impendance is 75 ohms
- The CSYNC voltage output is logic level (0V to 5V) and its output impendance is very low
Which CSYNC setting should you use? Well, SCART cables are supposed to include a 470 ohm resistor in series with the CSYNC signal in order to reduce the CSYNC voltage to video levels. If your SCART cable includes this value then set your CSYNC jumper to TTL. Some SCART cables only include a 75 ohm resistor in series with the CSYNC signal which does not reduce the CSYNC voltage to video levels and can potentially damage some equipment like the Framemeister. If your SCART cable include a 75 ohm resistor on the CSYNC signal then set your CSYNC jumper to 75.
The dbGrafx Booster is compatible with the following consoles.
- PC Engine
- Core Grafx