Sonic Adventure DX cheats and cheat codes for Gamecube

Zoom in Sonic Spinball
After you entered to the "Sound Test" option for Sonic Spinball, play the 
following music in order: 0, 2, 1, 1, 6, 6.

No gravity in Sonic Spinball
After you entered to the "Sound Test" option for Sonic Spinball, play the 
following music in order: 0, 9, 0, 1, 6, 8.

Faster background music in Sonic Spinball
After you entered to the "Sound Test" option for Sonic Spinball, play the 
following music in order: 0, 4, 2, 5, 5, 7.

Select stage in Sonic Spinball
After you entered to the "Sound Test" option in Sonic Spinball, play the 
following music in order: 0, 2, 1, 5, 6, 6.

Select stage in Sonic Labyrinth
Push Up, Up, Right, Right, Right, Down(6 times), Left(9 times) on your 
controller when the when "Press Start" text appears at the Sonic Labyrinth 
title screen.

Select stage in Sonic Chaos
Push Up, Up, Up, Up, Right, Left, Right, Left, Start buttons on your 
controller when the "Press Start" text appears at the Sonic Chaos title 
screen.

Select stage in Sonic The Hedgehog 2
Enter to the Sonic The Hedgehog 2 title screen. You will see Tails and he 
is blink with his eyes. He is blink first once, then blink again two times 
quickly. Keep held Down/Left + A + B buttons and push Start just when his 
eye shuts on the second blink of the double-blink.

In-game reset:
While palying, hold Start + A + B + X buttons for short time.

Unlock Super Sonic
Finish the game using all 6 default starting characters to play as Super Sonic.

Unlock Metal Sonic in trail mode:
Find all 130 Emblems to play as Metal Sonic.

Unlock Tails
Get Tails during the game in story mode, when obtained him use the 
controller-2 to play as Tails.

Unlock Mission mode option at the main menu:
Play in adventure mode and finish the game with all characters

Instant Chaos Emeralds in Sonic Chaos:
Push Up, Down, Up, Down, B, A, B, A, B, A buttons on your controller while 
you are at the Sonic Chaos character selection screen.

Sound Test in Sonic chaos:
Push Down, Down, Up, Up, Left, Right, Left, Right, B, A buttons on your 
controller while you are at the Sonic Chaos title screen.

Game Gear/Master System games:
To unlock a new Sonic mini-games, finish 10 missions or collect emblems.
Every 10 completed mission will unlock new mini-games in the "Mini Game 
Collection" option at the main menu. When you complete all of the 50 
mission you will unloc all minigames, including Dr. Robotnik's Mean Bean 
Machine, Sonic Chaos, Sonic Drift, Sonic Spinball, Sonic The Hedgehog. 

2-player in Game Gear mode:
Hit the Start button on controller-2 to bring up the another Game Gear 
screen for player 2. Note all game supported the two player mode.

Smaller Game Gear screen:
Push L + R trigger. Press the L + R trigger again to return to normal view.

Unlocks:

Unlock Mission Mode 
Finish the adventure mode with each character to get access to the 
Mission mode at the main menu.

Unlock Game Gear version of Sonic 1 
Pick up 20 emblems

Unlock Game Gear version of Sonic Drift 
Pick up 40 emblems

Unlock Game Gear version of Sonic Chaos
Pick up 60 emblems

Unlock Game Gear version of Sonic 2 
Pick up  110 emblems

Unlock Game Gear version of Dr. Robotnik's Mean Bean Machine 
Pick up 120 Emblems

Unlock Sonic Spinball 
Pick up 80 emblems. 

Unlock Sonic Labyrinth 
Pick up 80 or 100 Emblems and finish 20 missions

Unlock Sonic Triple Trouble 
Pick up all 130 emblems

Unlock Sonic Drift 2 
Pick up 130 emblems and finish 20 missions

Unlock Tails's Sky Patrol 
Pick up all 130 emblems and finish 40 missions.

Unlock Tails Adventure 
Pick up all 130 emblems and finish all 60 missions.