nfg.forums

After following several threads and tutorials on modding Sega consoles, I decided to mod my PAL Mega Drive 2 and Master System 2 for S-Video and line-level audio. The results for the Mega Drive were great, but I'm struggling to get good sound from the Master System.

My MS2 comes with just an RF output by default, so pretty much any av mod is a good mod.
It has a CXA1145P chip, from which I can get the Y and C signals (required for S-Video) and the audio if desired.

I found the Y signal needs a voltage follower amplifier as described at http://gamesx.com/wiki/doku.php?id=av:genesis_1_s-video_mod, but the C signal works well with just a 75ohm resistor and a 220uF capacitor.

The problem is getting sound at a decent volume. When using the RF module, sound comes through nice and loud if not clear. So far all points on the board where I can get audio result in a clear but very quiet signal. I've followed it from inside the RF modulator right back to the source (pin 15 of the 315-5246 processor), and everywhere seems to have the same quiet sound level relative to ground.  My guess is that the RF modulator might be amplifying the audio signal after it's been modulated.

Just wondering if anyone has managed to overcome this? Is there another reference I should be taking instead of ground for example? Or do I just need to put up with turning up the receiver to full volume to play Alex Kidd? 

thanks,

That's odd, I used the same audio source as you and the volume's fine. I suppose you could try taking audio from the CXA1145P (pin 9, "audio out" if I recall correctly.)

Hi,

I've already tried that, with the same result.  The Audio In and Audio Out pins seem to have the same level.  Did you remove the RF modulator from your SMS?  I wonder if that might be sinking enough current to drop the level?  I'd rather not remove mine unless necessary, but if it will fix this problem...

thanks,

I used couple of transistors to amp up the signal.

Quote from: trimbonz on August 09, 2008, 11:24:56 PM
Did you remove the RF modulator from your SMS?

My RF modulator's still in there. Maybe I just have a different idea for what quiet is :p