Question: Name the rectifier for Det/Pre-amp of X and # tubes of 4
SQL: SELECT "Rectifier" FROM "2-1211626-1" WHERE "Det/Pre-amp" = 'X' AND "# Tubes" = '4';

Question: Name the # tubes with Det/Pre-amp of X and audio amp of X X (push-pull)
SQL: SELECT "# Tubes" FROM "2-1211626-1" WHERE "Det/Pre-amp" = 'X' AND "Audio Amp" = 'X X (push-pull)';

Question: Name the det/pre-amp with # of tubes of 8
SQL: SELECT "Det/Pre-amp" FROM "2-1211626-1" WHERE "# Tubes" = '8';

Question: Name the det/pre-amp with # tubes of 4 and rectifier of X
SQL: SELECT "Det/Pre-amp" FROM "2-1211626-1" WHERE "# Tubes" = '4' AND "Rectifier" = 'X';

Question: Name the # tubes with audio amp of X
SQL: SELECT "# Tubes" FROM "2-1211626-1" WHERE "Audio Amp" = 'X';