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

### Instruction:
Name the rectifier for Det/Pre-amp of x and # tubes of 4

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

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