Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
Name the det/pre-amp with # tubes of 4 and rectifier of x

### Inputs:
table_name: table, columns: ['# Tubes', 'Converter', 'Det/Pre-amp', 'Audio Amp', 'Rectifier']

### Response:
SELECT Det/Pre-amp FROM table WHERE # Tubes = 4 AND Rectifier = x