I changed my Sega Genesis 2/CD 2 power cable situation after watching the My Life in Gaming video showing off using the PS2 slim power adapter for all your barrel jack based consoles. This is an 8.5V 5.65A PSU so it has plenty of juice for a Genesis + CD combo. I got some cheap power cable extensions from AliExpress and then a 1 to 2 splitter to put on the end, plus a polarity inverter for the CD side to make it center negative. I get a noise that sounds like someone breathing into a lapel mic, along with distortion on the video brightness and buzzing noises, whenever the CD is being accessed, only under certain setup conditions. I'm testing with Sonic CD and when I pause you can hear the buzzing, and then if you wait long enough for the CD drive to spin down, the buzzing stops (I did not wait long enough in the below video). Short recording of what I'm experiencing: https://drive.google.com/file/d/1bea...ew?usp=sharing The problem only occurs when I am powering both consoles off of the PS2 power supply, WITH an extension cable plugged in before the splitter at the end. I do NOT get problems when: - I remove the extension cable and have the PS2 PSU plugged straight into the splitter - I try using a PSOne PSU for the Genesis 2, and the PS2 PSU for the Sega CD, which works fine with OR without the power cable extension on the PS2 PSU. I have the big metal connecting plate with prongs for the bottom of the Genesis 2, but neither of the other 2 small metal shield pieces (that most people seem to say aren't necessary). I also tried some additional conductive material (carefully jamming tinfoil) connecting each console's ground shields to make sure that the ground connection was solid, with no change. I should also note my Genesis 2 has a triple bypass mod board installed and that playing Genesis games with everything setup the same sounds perfectly clean. The RCA audio jacks off of the Sega CD have the same problems (and also sound way worse in general because they don't use the triple bypass amp). Have a cap kit for both systems on the way so I'll be trying that first.
Sounds like power causing internal audio issues. The solution is to either stop using the extension cable or use separate PSUs based on the information you provided.
Sure it's a power issue, but what's actually happening? The Sega CD is the only console with this problem. A separate PSU is inconvenient and the extension is necessary to reach the consoles, and again the extension is fine if a separate PSU is used. It's just the combination of factors.
The combination results in power problems. Say for example the supply voltage drops too much you can have issues when a mechanical part draws more power and causes other parts of the system to have problems with increased noise. Another factor is the PSU becomes too noisy and parts of the system that aren't as well engineered to filter it out begin to let that through. 8.5 volts is little low for both these consoles and can result in some problems as well. Usually you want to be measuring stuff with a multimeter when doing this kind of thing. I have an all model 1 (Genesis+CD+32X) tower of power that I use three separate power bricks for. I use a separate surge protector for the whole thing and it works out nicely. It's not inconvenient at all and I get an extra switch that I can flip if I won't be using it to cut down on power usage.
Okay, that got me thinking! I measured input and output voltage on the CD 2's regulator under different conditions. Output was relatively stable, around 4.9V which isn't dead-on perfect but should be within tolerance for things. The input voltage I was getting varied quite widely though- with no extension and a separate PSU for the Genesis I got as much as 7.5V in, and powering both consoles with the extension cord plugged in it got down to 6.78V. If I have the right datasheet for the CD 2's regulator (NEC2405 is what I saw mentioned online) the minimum input voltage required is 6V. If the voltage is dropping so much just from using these super thin extension cables, I could imagine it getting close to the 6V minimum threshold for the voltage regulator once the disc drive is spun up and actively reading- the voltage getting this low could certainly cause weird audio/video noise issues. The voltage difference from the PSU between powering one or both consoles without the extension cords was just 0.08 so that's not that crazy of a drop from load (though I don't know why I'm not closer to the expected 8.5V, unless measuring at the regulator there's already been a voltage drop). Obviously these cables aren't worth a damn, but I really was just more interested in finding the root cause of the problem. They'll be in the garbage soon!
