RCA BA86-b Variable MU Tube Compressor (Vintage)

RCA BA86-b Variable MU Tube Compressor (Vintage)

Rare vintage RCA 86-b tube compressor limiting amplifier in great working condition. This predates the classic RCA BA6A.  The BA86 “Vari-MU” was originally used as a broadcast limiter in the 1950’s.  It has tons of gain and produces a rich warm compression it has become a desirable alternative to a Fairchild 660.  Big, huge sounding this unit is fully operational and quiet.

The RCA BA86 was originally designed in the 1950’s for use in the speech input channels of FM and AM broadcast limiters. It was also used for Disc cutting applications.  The BA86 uses 6K7 Pentode tubes and a ST4 rectifier.  Since the original plug-in style electrolytic capacitors are no longer available this unit has been recapped internally from the tube sockets.  The meter was designed to read 1) Gain Reduction 2) Dynamic match indicator for all input tubes  3) Measurement of all tube plate currents 4) Measurement of plate voltage.

There is enough gain 60dB to drive mic signal so we can set up a proper output pad for the unit if anyone is interested.