SYREN is a classic sounding tube preamp in a 500 series package, using a dual triode circuit with a 12AX7 tube

SYREN features a dual gain stage circuit and allows overdrive effects.
A switch selectable HI-z input is included.  The low cut filter is at 90 Hz and is 24 db/ octave.  The pad has
-15 db and -25 db settings to allow a wide input range of signals.

The audio path color is changed by modifying the second stage tube circuit so it has negative feedback or does not have negative feedback.  This changes the interaction between the tube stages and thus the sound of the pre-amp.  With negative feedback it is a more accurate audio path with wider frequency response and without negative feedback it has a more open warmer sound.