Audio: prosound & FM mod¶
Two common audio mods: prosound (getting clean sound ahead of the noisy headphone amp, especially on handhelds and older consoles) and the FM mod (adding the YM2413 chip to an export Master System that lacks it).
Prosound¶
| Field | Value |
|---|---|
| Systems | Game Boy (DMG/GBA), Mega Drive, PS1… |
| Type | clean line output before the headphone amp |
| Level | 🟡 fine soldering (points upstream of the pot/amp) |
Principle¶
The original headphone amp (especially Game Boy, Mega Drive 1) adds hiss and crosstalk. Prosound taps the audio signal upstream (before the volume pot and the amp), for a clean line output — sought after by chiptune musicians (LSDj, etc.).
Variants¶
- Direct prosound: tap before the pot (volume handled downstream).
- Prosound after the pot: keeps the physical volume control.
- Often paired with a new jack socket on the front.
Mega Drive 1: prosound = Triple Bypass
On MD1, the Triple Bypass already includes the clean audio bypass — no need for a separate prosound.
FM mod (Master System)¶
| Field | Value |
|---|---|
| System | export Master System (lacking the FM) |
| Type | adding the FM YM2413 sound chip |
| Level | 🟠 soldering (chip + switching logic) |
Principle¶
The Japanese Mark III / Master System have a YM2413 FM chip that gives an enriched soundtrack on compatible games. The export versions lack it (PSG only). The mod adds the YM2413 + the logic so games detect it → FM music instead of the PSG.
Before / after (FM)¶
| Criterion | Export SMS (PSG) | With FM mod |
|---|---|---|
| Music (compatible games) | PSG beeps | rich FM (organ/synth) |
Where to buy¶
- Prosound: nothing to buy (wires + jack); guides in the Game Boy/MD communities.
- SMS FM mod: a YM2413 chip (distributors/salvage) + community kits/PCBs (see RetroRGB / SMS forums).
Sources & attribution¶
- RetroRGB — prosound and Master System FM dossiers — https://www.retrorgb.com/
- Console pages: Master System · Game Boy
Review & corrections
How this space is used
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