API 3124MB+ 4-Channel Preamp W/Stereo Pan


The API 3124MB+ 4-channel microphone and instrument preamp packs API console sound and performance into a very easy-to-use, premium-quality rackmountable unit — complete with a built-in stereo mixer!.

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SKU: API3124MB Categories: , Brand:

The API 3124MB+ is a four-channel, all-discrete mic amp featuring the same 312 preamp circuits used in all API consoles, plus an additional 4-channel mixer with transformer balanced output

For anyone who’s ever lusted after an API console but didn’t have a piggy bank that could hold 15 million pennies, considerably less gets you a 3124MB+; four channels of API console preamps featuring the API 2520 Op-Amp, responsible for API’s signature sound. Designed for the highest possible performance, even with the lowest sensitivity mics the 3124MB+ provides clean, noise-free gain up to 65dB to an output clip level of +28dBu. Since the front-panel Hi-Z input is routed directly to the 2520 op-amp, a guitar or bass with low-output passive pickups can be amplified without a matching transformer or direct box. With the ability to accept input levels up to +20dBu, the Hi-Z input can also handle high-output instruments such as keyboards, or guitar and bass with active pickups. While the API 3124MB+ shines on any sound source, it’s a particular favorite of engineers for tracking snare and toms with lots of punch.

API 3124MB+ Mic Preamp In one take

  • Uses the API 2520 op-amp, responsible for the API signature sound
  • Stereo output mixer with pan control
  • Classic console circuit
  • Four XLR Mic Inputs
  • Four 1/4″ unbalanced inputs
  • Front-panel polarity switch
  • Front-panel 20dB pad switch
  • Front-panel mic/line switch
  • Front-panel 48V power switch
  • Output clips at +30dBm


The 3124MB+ is designed to provide the professional engineer with the highest possible quality. A 4-channel mic preamp, the 3124MB+, adds a stereo mixer with a transformer balanced output. It has the same microphone preamp circuit found in all API consoles, the RE-115 K mic-input transformer and the same output transformer used in API equalizers. The 3124MB+ has an internal 48-volt phantom power supply for each channel, switchable from the front panel. It also has a front-panel -2 dB pad switch that attenuates both mic and line inputs. On the rear panel, each channel has a 1/4″ TRS jack that functions as an insert (tip-send/ring-return) between the mic preamp output and the mixer input.

The 3124MB+ allows up to 65dB gain for use with low-sensitivity mics, such as ribbon mics, to an output level of +28dBu. The Hi-Z front-panel input goes directly to the op-amp, which enables low-output instruments, such as vintage guitars or basses with passive pickups to be amplified without a matching transformer or direct box. Extremely versatile, the Hi-Z input can also accept high-output signals up to +20dBu, making it perfect for keyboards and other high-output instruments.

The 3124MB+ makes multi-mic tracking convenient with the addition of stereo pan with a level control and post-fader aux send. The stereo pan and aux sends are bussed to master output controls and then to the rear-panel outputs. A stereo aux return is provided to return effects or cascade additional mixers for more inputs. The unique stereo aux return control acts to balance the left/right signal, while maintaining the stereo field. It can also be used as a mono return.


Each preamplifier provides a comprehensive suite of front-panel controls:

 GAIN: Preamp gain

  • POL: Preamp input polarity inverter
  • 48V: Phantom Power
  • PAD: ‐20 dB microphone pad/‐6 dB instrument pad
  • MIC: Mic‐Instrument input selector
  • HI‐Z IN: 1⁄4” high‐impedance instrument input
  • LEVEL: Stereo mixer send level
  • PAN: Stereo mixer send pan
  • AUX: Auxiliary bus send level
  • VU METER: 7 LED VU meter

Rear-panel I/O:

  • 4x XLR inputs
  • 4x XLR outputs
  • 4x 1/4″ TRS inserts
  • 2x 1/4″ out
  • 1x 1/4″ send
  • 1x 1/4″ return
  • Universal IEC connector

The 3124MB+ is equally at home in the control room, studio, recording truck, or on stage. For more information, call or chat online with your Westlake Pro Sales Consultant today.


API 3124MB+ specifications

  • Input Impedance: Mic: 1500 ohm Unbalanced: 470k ohm Hi‐Z
  • Output Impedance: Less than 75 ohm channel outputs
  • Nominal Levels: LR Channel Output +4dBu
  • Stereo Output Level: Balanced: +4 Unbalanced: Nominal ‐2
  • Clipping Level: XLR Channel Output better than +28dBm
  • Frequency Response: +0, ‐5, 10 Hz to 20 kHz (‐0.5 at 10 Hz)
  • Noise EIN: Mic: ‐129; Unbalanced Actual: ‐129
  • Measured Noise: Better than ‐91dBm/Below Nominal +4
  • Distortion: All Outputs at +4 Out, 0.03% All Outputs at +22 Out, 0.09%
  • Gain Range: 150 ohm Input: 10dB Min, 65dB Max (Incl. PAD) Unbalanced Input: 14dB Min, 50dB Max
  • VU Meter: Calibrated for XLR Outputs, OVU = +4 dBu (‐12, ‐6, ‐3, 0, +3, +6, +18)
  • Controls: GAIN, PAD (20 dB), 48V (Volts), POL (Polarity), MIC (Mic/Unbalanced), VU, AC
  • Power Consumption, Quiescent: 2 watts
    Size: 19″ × 1-3/4″ × 10-1/2″
  • Size (Boxed for Shipping): 23-1/4″ × 6-1/2″ × 16″
    Actual Weight: 54 lb.
    Shipping Weight: 15.3 lb.

Additional information

Weight 11 lbs
Dimensions 19 x 9 x 5 in

4 x XLR, 1 x 1/4" (Aux Send), 2 x 1/4" (Stereo Out)

Channel Count



4 x XLR (Mic), 4 x 1/4" (Hi-Z), 1 x 1/4" (Aux Return)

Rack Spaces


Phantom Power



1.75 x 10.5 x 19


11.5 Ibs


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