Requisite Audio OS1 Preamplifier MK II
The OS1 was developed around the 6SN7 vacuum tube. The 6SN7 was developed in 1939 and, over the years, has become my personal favorite and often considered king of the general-purpose audio triodes. High headroom and broad frequency response are the hallmarks of the OS1. The OS1 can drive a 600-ohm load at a +40dB output and has an internal frequency response of 10Hz to 600,000Hz. This is a very special microphone preamplifier, designed especially for the most demanding audio professional.
Variable Microphone Impedance
Microphone input impedance is selectable using a six-position rotary switch. Available Impedances are: 50, 200, 300, 600, 1200 and 2400-ohms.
Variable High-Pass Filter
Low frequency response can be contoured with the variable High-Pass Filter. Positions available are: Flat, 35Hz, 70Hz and 120Hz, each with a slope of 12dB per octave. Frequencies are selected via four-position rotary switch.
Variable VU Meter Range
For monitoring the OS1’s prodigious output capabilities, Meter Range is selectable using a three-position rotary switch with +4dB, +10dB and +20dB ranges. Each position has it own calibration trimmer which can be adjusted to any level desired. As an example: the +20dB position can be calibrated to 0dB = +28dBFS. With the OS1, you still have 12dB of headroom beyond that!