If you find a Genesis 2 that has a shorter metal plate under the system through the air vents, those are the VA3/VA4 versions with the clean audio. Older Model 2s will also have super-shitty video; it's blocky, pixellated as all hell, blurred, and has the same line noise problem as a Top-Loader NES, but to a lesser extent(not as many vertical lines visible). I did notice something, though: if you take a VA0-VA1.8 Genesis 2 and hook it up to a Sega CD, if you use the sound output from the Sega CD instead of the Genesis, the sound is filtered, though the quality doesn't improve.
Allow me to explain in detail the sound problem: while every Genesis has a YM2612 in different formats, either integrated within one of its chips or as a separate chip, it's not the cause of the nasty audio. As mentioned before, it has to do with other parts of the circuitry. The problem lies within the sound amplifier. For whatever reason, when the Genesis Model 1 got the VA7 motherboard in it, the sound amplifying circuitry Sega used caused the sound quality to drop drastically, to the point where it would distort some of the sound. To make matters worse, it also induced static. Some Genesis 2s made in China actually FURTHER EXACERBATE the problem by changing some things around in the sound circuit that further distorts the sound to the point where some low-pitched sounds are output as squeaks. Here's a rundown on the sound quality plus a general description of the sound amplifying circuitry:
-Genesis Model 1 with High Definition Graphics(motherboard revision VA0-VA6, contain EXT port): these use a discrete YM2612 with a sound amplifier that filters the sound to give it more bass. Sound quality is exceptional.
-Genesis Model 1 without High Definition Graphics(VA6-VA7 motherboard revision): some of these are identical to the Genesis Model 1 with High Definition Graphics, but as mentioned before, VA7 motherboard revisions contain a sound circuit that drastically lowers the quality of the sound output and induces static. The VA7 revision uses a YM2612 integrated within an ASIC on the motherboard.
-Genesis Model 2 with full motherboards(revisions VA0-VA2): VA0, VA1 and VA1.8 Genesis 2s use a YM2612 integrated within an ASIC like the VA7 Genesis Model 1 and use the exact same super-shitty sound circuit found in there. Some VA1.8s, as previously mentioned, tend to distort the sound even more, which are made in China. VA2s have a discrete YM2612, which sounds like a Genesis Model 1 with High Definition Graphics, but with less bass. The big problem with this Genesis 2 is in its tuning of the sound outputs. The YM2612 is too loud compared to the other sound channels: Genesis PSG, Sega CD PCM/CD-DA, and 32X PWM. Not only that, the PSG sound channels are out of tune, with some sound channels being louder or quieter than their supposed to be, which may be as a result of using a different sound amplifier than the Genesis Model 1 with High Defintion Graphics.
-Genesis Model 2 with 3/4 motherboards(VA3 or VA4 revision): These use a revised sound circuit that sounds almost like the High Definition Graphics Genesis Model 1, but with MUCH less bass and a much lower decay rate(you hear the sound channels echoing less). Its quality is the best out of all Genesis 2s. These use a YM2612 integrated in an ASIC.
There's a common trend among the ASIC-based YM2612 in which they have a lower decay rate than the discrete YM2612, and it does actually output slightly clearer sound than the discrete YM2612 when properly amplified.
You'd be better off with a High Definiton Graphics Genesis Model 1, though. Nothing can beat its high-bass sound, except TmEE's Audio Mod circuit for the VA7 Genesis Model 1 and VA0-VA1.8 Genesis 2 for some(I personally prefer high-bass sound).
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Originally Posted by Tain
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