Name the det/pre-amp with # tubes of 4 and rectifier of x
CREATE TABLE table_name_56 (
    det_pre_amp VARCHAR,
    _number_tubes VARCHAR,
    rectifier VARCHAR
)
SELECT det_pre_amp FROM table_name_56 WHERE _number_tubes = "4" AND rectifier = "x"
Below are sql tables schemas paired with instruction that describes a task. Using valid SQLite, write a response that appropriately completes the request for the provided tables. ### Instruction: Name the det/pre-amp with # tubes of 4 and rectifier of x ### Input: CREATE TABLE table_name_56 (
    det_pre_amp VARCHAR,
    _number_tubes VARCHAR,
    rectifier VARCHAR
) ### Response: SELECT det_pre_amp FROM table_name_56 WHERE _number_tubes = "4" AND rectifier = "x"