This is the first original amplifier card used in the early 919 stereo control center later referenced as a mixer. This first card electronic design was going to be used in the CMA 10-2DL but required redesigning to physical fit the new DL chassis. Both main and monitor outputs had the same db gain. 

This was the first update to the 919 audio card. The part number became 1.919.225-11 and retained the same audio output characteristics. It replaced the original 919 card and was the first output amplifiers used in the CMA 10-2DL mixer. A variable resistor replaced the original fixed resistor for critical adjustment's. 

Bozak engineers toyed with output characteristics on the early DL mixer and for a couple years unadvertised db and output gains increased. The main change involved circuitry increasing the headphone drive output. The first updated equal stereo gain card remained as the 3rd amplifier option. It became known as the Booth card.    

In 1976 the VR changed on schematics and customer copy’s but few cards actually received it. This change was for precision output adjustments. 

Beginning in the 1960s Bozak mixers were coupled with external Zone controls in churches, restaurants, hotels, schools, bars, and even the NewYork Philharmonic Stage. Some controls were simple “bud box’s” while others were elaborate professional built control panels. Nonetheless it was the origin of controls for other areas. Many installers modified Bozak mixers with extra outputs, but it wasn’t u

The original 470 ohm resistors in the photo positions R7 and R27 produce roughly 6 volts and +22 db. The next change was the R7 and R27 to a 220 ohm resistor. This produced closer to 13 volts and +28db but was advertised as +24db.