Inspired by the classic American rock sound of the original API® 312A, the B12A MKII delivers the high-end sound and rugged quality you’d expect from B.L.A., at an amazing price! The B12A MKII is a single-channel microphone preamp in the style of an API® 312A, and features an upgraded input transformer, higher gain, and lower noise than the original B12A. It also features an output transformer, a Hi-Z input, phantom power, pad, phase, and is housed in a 1U, 1/2 rack chassis.
POWER: flip switch up to turn preamp on, flip switch down to turn preamp off
48V: engage to turn phantom power on, disengage to turn phantom power off
PHASE: engage to adjust input signal polarity by 180°, disengage to leave input signal polarity unchanged
PAD: engage to reduce input signal amplitude by 18dB, disengage to leave input signal amplitude unchanged
GAIN: clockwise rotation yields an increase in output signal amplitude, counterclockwise rotation yields a decrease in output signal amplitude
Hi-Z: engage to use front panel Hi-Z IN as preamp source, disengage to use XLR input as preamp source
Hi-Z IN: input jack for use with high impedance, unbalanced sources (GAIN knob adjusts signal amplitude)
OUTPUT: balanced, line-level TRS output
INPUT: balanced, mic-level XLR input
GND: internal chassis ground
POWER: 24VAC input jack (only use a B.L.A.-specified power supply)
FEATURES
Cinemag Input Transformer
Edcor Output Transformer
70dB Gain
Hi-Z Input (passive, unbalanced)
Phantom Power
18dB Pad
Phase Switch
XLR Microphone Input
TRS Line Output (balanced)
Mic Section
Max Microphone Input Level: +1dBu
Input Impedance: 200Ω
Pad: 18dB
Gain (no pad): +26dB to +70dB
Equivalent Input Noise (noise floor): -120dBu
THD+N (@ +4dBu output):
.012% @ +22 dBu
.013% @ +36 dBu
.046% @ +56 dBu
.145% @ +66 dBu
Bandwidth (1kHz, 150Ω source, unweighted): 10Hz to 30kHz
D.I. Section
Max D.I. Input Level: +18dBu
Input Impedance: 1.1MΩ
Pad: none
Gain: +10dB to +53dB
Equivalent Input Noise (noise floor): -102dB
THD+N (@ +4dBu output):
.013% @ +10 dBu
.124% @ +36 dBu
Bandwidth (1kHz, 600Ω unbalanced source, unweighted): 10Hz to 30kHz