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Genesis/Mega Drive sound chip comparisons?

Discussion in 'General Sega Discussion' started by AeonicB, Sep 18, 2022.

  1. AeonicB


    I was talking to my sibling, and they wanted an easy way to check sound chip differences between systems. However, my old favorite standby, Tomczak's page, is offline, and the Wayback Machine doesn't seem to have archived any of his files.

    Does anyone know of another reference so I can show them?
  2. Chimes


    The One SSG-EG Maniac Member
    This is... kinda a tricky question. Despite the efforts of countless people over the years, there isn't exactly a "central hub" for checking what differences a different sound chip produces in a Genesis, with many attempts not exactly being helpful to the untrained ear: stuff like the Tomczak page unfortunately don't really show the differences of the two consoles, they just have descriptions and clips that don't show something that is actually different outside of being muffled or not. But judging from my experience and tons and tons of talking to people about examples to use, the best way to tell what sound chip a Genesis uses with video game music is to use a game that:

    1. is very quiet in volume
    2. has certain sounds that heavily use treble (i.e. high pitched noise)
    3. was released before the year 1993

    Games made before the year 1993 is guaranteed to sound different from the two chips, because of the Model 2 releasing later that year and some developers later using the Model 2 for game development. This isn't always the case, though: it's possible some composers still used a Model 1 for development after 1993 but there's no way to tell.

    I've been told that from console to console, the Genesis has different low pass filters for the audio output. Some games were written with a muffled sound in mind: others were written with a clear sound in mind. It's kind of subjective, unless the composer/sound designer specifies what version of the Genesis they used.

    The Model 1's chip, the YM2612 had a hardware bug known as low volume distortion which affects quiet sounds. Every game had to be written around a broken volume curve, which was fixed in the YM3438. This caused some games to have their volume mixing to sound strange, with instruments fading a bit too quickly.

    Because there isn't exactly a list that details what games use quiet volumes and hissy noise, it can be quite tricky to pin down a game that sounds different from one sound chip to another. But I do have a few examples:

    Hellfire and Earthworm Jim have a strange bug from system to system that alters their note timings and tempo. The chip responsible isn't what caused it: rather it's the system itself? It's strange.

    Thunder Force IV has a lot of muffled treble in the guitar instruments that sounds different from system to system (infamously, emulation recordings have all the treble, resulting in a very painful listening session to anyone under the age of 19).

    Earthworm Jim 2 has a song that sounds different from the two sound chips. The YM3438 plays the notes as intended, but the YM2612's LVD causes this strange snarl/growling timbre to affect the background notes, due to the notes sustaining a lot longer than expected.

    After Burner II uses LVD to even out the volume mixing, which was fixed in the YM3438. Certain songs have instruments that become inaudible or too quiet on a YM3438, with Red Out using a high pitched sound that gets muted.

    BATMAN is a game that is quiet, but uses the LVD in a interesting way: it uses it much like ABII, by levelling volume mixing and instrument volume decay. As a result, some songs in the game have sounds that fade out way too quickly.

    Streets of Rage 1 and 2 have some certain songs that are very quiet: as a result, they get subject to LVD. Good Ending's coda has a pair of piano chords, where they progressively "buzz out" on a YM2612. On a YM3438, they fade out. SOR Super Mix in particular has a pair of piano notes that from console to console have their volume change: on a YM2612 they sustain a lot longer, but on a YM3438 they fade out as intended. This can be seen by using a oscilloscope and checking the piano sounds.

    As a post-1993 game, Toy Story doesn't seem to use LVD, but one song sounds different between the two consoles: there's a pair of sustained notes in Sid's Workbench that last longer. They fade quickly on a YM3438.

    Ecco the Dolphin is a game that sounds slightly different from the two consoles: several of the background music's synth pads and sustained notes last a lot longer and have a buzzy texture on a YM2612. On a YM3438, they fade out sooner and the sound is a lot "cleaner".

    Richard Scarry's Busytown is a bizarre example: on a YM3438, the music plays as intended, but the game's audio is SUPER quiet. This... is a recipe for disaster. On a YM2612, virtually every instrument gets crunched down to a buzzy soup that is unpleasant to listen to.

    Altered Beast doesn't use LVD, but two sound effects partially break on a YM2612: using the sound test, by playing sound entries BE and BD, there's a strange pulse that is inaudible on a YM3438.

    Beyond Oasis has a song that's known for sounding different from console to console: Evil Territory. For some strange reason, this song is very quiet and has some volume fades: causing what can only be described as buzzy noise chomping down on the sound on a YM2612.

    Alex Kidd in the Enchanted Castle
    doesn't really use LVD, except in some strange instances: Scopaco Cycle uses it to bring out a background melody, and Splashy Sea has this hiss in the background.

    World of Illusion is a game that sounds a teeny bit different from console to console: its reverby sound design is slightly accentuated on a YM2612 with phantom pulse waves being generated on some songs, but on a YM3438 it sounds slightly "flat", for a lack of a better word.

    Sonic 3D Flickies' Island is mostly the same from console to console, except for The Final Fight: for some reason, the YM2612 bugs out with stereo panning. This causes a strange background buzz in this one bar in particular. The YM3438, meanwhile, doesn't have this buzz.

    That's just many of the examples using video game BGM that I can think of. There might be others I've missed, but these should do.
    Last edited: Oct 19, 2022
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  3. Chibisteven


    ~ Model 1 ~
    VA0-VA2 - Loud games suffer a little when they get loud. All models are prone to background mains hum with stock AC Adaptor. Uses YM2612.
    VA3-VA6.8 - Different lowpass, loud games no longer suffer. The most common model 1 audio circuit and probably the best model 1 stock circuit. Some models are prone to mains hums with stock AC Adaptor and others are kind of prone to picking up video sync noise (around 15 KHz). Uses YM2612.
    VA7 - Bad stock sound circuit. Uses ASIC YM3438.

    ~ Model 2 ~
    VA0-VA1.8 - Bad stock sound circuit and it can really vary depending on opamps used. The most common model 2 audio circuit. Uses ASIC YM3438.
    VA2 & VA2.3 - Bad mixing circuit, YM2612 is too loud. Uses YM2612.
    VA3 - Good sound circuit. Uses ASIC YM3438.
    VA4 - Good sound circuit. Uses GOAC YM3438.

    ~ Model 3 ~
    VA1 - Mono Only Circuit. Uses GOAC YM3438.
    VA2 - Mono Only Circuit. Uses GOAC YM3438.

    ~ Nomad ~
    Okay Sound Circuit, PSG is slightly louder than it should be. Prone to picking up mains hum with stock AC Adaptor, fine on batteries, some internal interference noise as well. Uses ASIC YM3438.

    YM2612 - Prone to quantization noise when the volume gets low. Prone to some soft pan bugs even though the chip only supports hard panning. Least amount of resolution.
    ASIC YM3438 - Less quantization noise than the YM2612. Some games can sound like stuff is missing where others simply sound cleaner. More resolution.
    GOAC YM3438 - Less quantization noise than ASIC variant. Some games can sound like stuff is missing where others simply sound cleaner. Most amount of resolution.
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