1947 RCA MI-12156 15-WATT AMPLIFIER - SERIAL 2592!  

THESE ARE THE AMPS JACK WHITE CONVERTS FOR HIS LIVE RIG!!

The RCA MI-12156 (this pre-dates the MI-12156-A and MI-12156-B variants) is a classic, post-World War II 15-watt vacuum tube public address (PA) / mixer amplifier manufactured by the RCA Victor Company starting in the late 1940s.

Originally designed for speech and mono record reproduction in venues like schools, churches, and auction houses, these units are highly sought after by musicians today for conversion into guitar amplifiers—notably popularized by Jack White, who used three custom-modified versions (referred to as "Clubmasters") as his primary stage touring heads.

Factory Specifications

Power Output: 15 Watts average

Power Requirements: 117 Volts AC (alternating current), 50–60 Hz.

Frequency Response: Rated conservatively for speech and phonographs at ± 2 dB from 50 to 7,000 Hz (typical of broadcast and PA standards of the era).

Dimensions:Standard model (MI-12156): 16" Wide × 7.5" High × 9.5" Deep.

Weight: Approximately 24 lbs depending on the specific enclosure/cover variation.

Tube Complement (6 Valves Total)

1× 6SC7, 1× 6SJ7, 1× 6SL7GT, 2× 6L6G (Output), and 1× 5Y3GT (Rectifier).

Input and Control InterfaceInputs: Features a total of three input channels -

2× Microphone Inputs: Typically paired with low-impedance plug-in input transformers (selectable between 30/50 ohms or 150/250 ohms) or wired with vintage multi-pin XLR inputs.

1× Phonograph Input: A high-impedance input designed for contemporary mono record players.

Controls: Front panel layout consists of:

• Microphone 1 Volume
• Microphone 2 Volume
• Phonograph Volume
• Bass Control
• Treble Control

Output Connections

Speaker Load Impedances: The output transformer features selectable output taps accommodating 4, 8, and 16 ohms.

Connectors: Original vintage 2-pin/bladed speaker connector jacks, which require conversion or special adapters to accept modern 1/4" speaker cables. 

TRANSFORMER EIN OF 138713 MARKS THIS A STANCOR TRANSFORMER MANUFACTURED THE LAST WEEK OF MARCH, 1947. 

THIS UNIT HAS HAD THE POWER CORD UPDATED TO A 3-PRONG GROUNDED CORD.