|Power||2x 6GW8 (power and phase inverter)|
|Vibrato||12AU7, (1/2) 7025, 2 varistor|
|Speaker||8" Oxford 3.2ohm|
The M4 has simple volume and tone controls, reverb, and a F.M.Vibrato unit mated to a single 8" speaker. Vibrato has speed and depth controls and a footprint jack. Reverb has a depth control and a foot switch jack. This was the entry level model amp.
The M2 is almost an M4 without reverb, the M4 has an extra 7025 triode gain stage in the preamp.
Because the 6GW8 contains a power pentode and a triode in the same glass envelope, Magnatone could use the two triodes for a phase inverter and install one less 12AU7 in the amp, thus lowering the manufacturing cost of these entry level amplifiers.
The M4 might have been dropped from the catalog when the Starlite Series was released in 1964. The 431 is very similar to the M4.