Two different amplifiers were available through Sega for the Prologue 21. The SKA-3000 has a pair of RCA terminals to accept stereo audio input, and four output channels are present for speaker connections. Two knobs on the front adjust balance and volume. The rear is branded as Nihon Columbia, the same as the SKC series Commander and SKW series changer. Approximately 10-15,000 produced.
The SKA-3100 is very similar, with added Super Prologue 21 branding and “Shakit” control to add bass and treble adjustments as well. This amplifier is branded as Clarion, and the rear layout is very similar to the Clarion MB-3000A. Approximately 5-7,000 produced.
An additional module, SKA-3800 could adjust bass and treble externally if the amplifier could not.
SEGA Prologue 21 