  In case you're wondering, the yellow fly-wire on the FM PBC connects the PAUSE button to the CPLD; this is what allows the user to enable or disable the FM feature. I anxiously took the picture of the 2 new boards before adding the fly-wire which is why it doesn't show on the pictures to the left. The change in opamps and resistor values in the opamp circuits (i.e. lower for less noise) did not seem to have any effect on the small perceivable noise on the audio output. The YM2413 Application Manual indicates the typical noise at the output to be -65dB! Holy hell, I may be fighting a lost cause against this. While I certainly don't think this small noise is a show-stopper, I would like to be able to reduce it as much as possible. In order to even notice it you need to use headphones on the Model 1 and set the volume slider to maximum. A simple test of removing the YM2413 from its socket (on my socketed prototype) has confirmed the source to be the YM2413. Oh well... Maybe I should look into running an RTL model of the YM2413 on an FPGA in a future version... I loaded a few ROMs on the Everdrive for initial testing: Phantasy Star (english translation), After Burner, Altered Beast and Ys all played the FM Music. More results to come later, now it's bed time! |
Home > Lab Updates and Posts >