The G9 is a dual true tube microphone preamp. It's a simple, yet powerfull unit, based on a variable-gain input tube stage driving a tube SRPP output stage. No silicon or other crap in the signal path.
The controls on the G9 are as follows:
The input level switch - in eleven steps - sets the raw gain of the first stage, thus allowing you to control the input level, the "drive" for the preamp.
The output level pot attenuates signal to the output stage, allowing you to fine-trim the output level going to the next stage in your signal chain
The input switch is used to select either Line, Mic, or Mic-with-P48 as input for the unit. If you insert a jack at the front panel socket marked "Inst.", this will break the signal selected on the input switch, and in stead have a very-high impedance instrument input - perfect for DI of e.g. bass guitar.
A gentle highpass filter of either 80 or 160Hz is activated by the "Low-cut" switch, and the unit's absolute phase can be reversed using the "Phase" switch.
The G9 is floating, transformer balanced at line and mic inputs, as well as on output. Input impedance for the mic input is some 1KOhm, line is some 10KOhm, Inst. >2MOhm, and output impedance is <1K Ohm.
Although semiconductors are used in this unit, they're confined to powersupply functions. At no time will your audio pass through anything but transformers, tubes and passives. So we're talking REAL tube audio here..