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Triple Bypass / Mega Amp (Mega Drive 1)

The reference AV mod for the Mega Drive Model 1: it short-circuits the stages that muddy the original image and sound (aging video encoder, noisy audio amp) to output clean RGB + audio. Designed by db Electronics, now open-source.

Field Value
System Mega Drive / Genesis Model 1 (VA0→VA7) — Mega Amp also useful elsewhere
Type video (RGB/csync) + audio bypass
Level 🟡 medium soldering (a few wires + daughterboard)
Reversible ✅ (added wiring, no chip removal)

Why the MD1 needs it

The Mega Drive 1 has two known weaknesses:

  1. Video: RGB goes through the Sony CXA1145 (or CXA1645) encoder which, with age and depending on the revision, gives a dark / slightly smeared image, and its csync is sometimes weak.
  2. Audio: the original headphone/line amp is noisy (hiss, crosstalk), especially on the early revisions with a discrete YM2612 (VA0–VA3, "crunchy" but noisy sound).

What the Triple Bypass does

  • Taps the RGB directly before the encoder (clean source).
  • Buffers/amplifies R, G, B + csync cleanly (video buffer).
  • Bypasses the original audio amp → clean line output (left/right).
  • Provides a new AV output (multi-out) wired for SCART.

The Mega Amp is the audio-only variant (if you just want to fix the noise problem without touching the video).

Compatibility (revisions)

  • Covers Model 1 VA0 to VA7. The wiring points vary by revision (DAC/encoder position) → follow the matching guide.
  • Model 2: cleaner out of the box, but has its own small mods (often a simple csync re-wire / filter removal). The MD2 mainly suffers on sound depending on revision.

Installation (summary)

  1. Identify the VAx revision (board silkscreen).
  2. Solder the RGB + sync wires to the indicated points (DAC output / encoder input).
  3. Wire the audio upstream of the original amp.
  4. Fit the daughterboard (buffer) and route to a multi-out.
  5. Add the clean csync for SCART (see RGB & SCART).

Before / after

Criterion Original MD1 With Triple Bypass
RGB brightness often dark correct level
csync sometimes weak clean and stable
Audio noise hiss / crosstalk clean line output
Output original DIN multi-out wired for SCART

Where to buy

  • Designed by db Electronics, now open-source (files on Tianfeng's GitHub, Zaxour's remix) — you can build it or buy it assembled.
  • Assembled boards: Insurrection Industries, RetroGamerStuff.
  • Illustrated per-revision step-by-step: ConsoleMods: Triple Bypass (CC-BY-SA); RetroRGB dossier — https://www.retrorgb.com/.
  • ⚠️ Expert and disables composite output in most cases; install per revision (Model 1 VA0→VA7, Model 2 VA0→VA4, Model 3, CDX).

Alternatives / complements

Sources & attribution

Review & corrections

How this space is used

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