Ability to change both the Feedback and Bias of the amplifier. 
The Feedback control increases harmonics thousands of times over the range of the control. 
High and Low input impedance; transformer balanced line in 
Discrete Transistor Class-A Circuitry 
Mono Channel 
Max Gain of 66.5db 
+48V Phantom Power 
300 Ohm or 1200 Ohm Mic Input Impedance 
10k Ohm Line Input Impedance 
 
Format: 500-series