API 3124+ – Four High-End Preamps In A Single Chassis

Written by Ed Lopez. Posted in Studio Gear

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image: API3124+

Published on March 08, 2013 with No Comments

API could be catagorised as one of the preferred choices for engineers and
producers in the music industry, best known for their unique designs of
amplifiers and consoles used extensively in recording studios as well as
in audio broadcast for radio and television networks worldwide. The API
3124+ is a high end, compact, four-channel mic pre-amp that offers a
classic sound together with essential features of modern recordings.

The 3124+ is based on the classic API 312 mic preamp. Its tone relies on
the famous 2520 discrete op amps, RE-115K mic input transformer, and
the API output transformer found in the 512C mic pre and throughout the
API product line. Additionally, its circuit design is similar to the classic
API console. This mic pre can be used for many different sources, such as
guitar, bass, vocal, piano, and much more. Using this mic pre for stereo
recording (such as drum overheads and choirs) is potentially very beneficial, because each chassis possesses two matched pair mic pres.

Each channel has a 48-volt phantom power supply, XLR input, XLR output,
Hi-Z instrument input (front panel), mic/instrument switch, -20dB pad
switch, polarity switch, and a LED meter. The Hi-Z inputs are routed
to the op amp, which allows low-level input, such as guitar
or bass, to be amplified without a direct box. Also, the Hi-Z’s capabilities
of taking up to +20dB makes it capable of receiving high-level inputs
from keyboards or other devices.

image: API 3124+ 4 Channel



The 3124+ are known to be a “hot” pre amp, meaning that besides
the included -20dB input pad, you can also add an output
pad (around -15dB) to the signal chain. This enables you to drive up
the pre-amps further, achieving the signature API “coloration” to your

This preamp could also be used to drive entire mixes through the mic
inputs. First, you have to calibrate the levels with a mono signal first
(sine wave generator recommended). Second, set at least -6dB pads
to have more room before overdriving the A/D (inputs of the audio
interface). Finally, drive the two inputs of the 3124+ equally to the desired

For €2,200.00 RRP, the API 3124+ offers a four-channel, high-end
mic pre that delivers the classic and unique API sound, with additional
capabilities much needed in today’s recording industry – and it take up only 1 U of space in a
rack mount.

A great little demo of the API 3124+ can be found here, courtesy of BlueroomsOnline.


Input Impedance: 1500 Ohms Mic, 470 K Ohms Un-Balanced, HI-Z in

Output Impedance: Less than 75 Ohms Channel Outputs

Nominal Levels: XLR Channel Output +4 dBu

Stereo Output Level: Unbalanced: nominal -2, Balanced: +4

Clipping Level: XLR Channel Output better than +28 dBm

Frequency Response: +0, -5, 10 Hz to 20 kHz (-.5 at 10 Hz)

Noise EIN: -129 Mic, -125 Un-Bal. Actual

Measured Noise: Better than -91 dBm / below Nominal +4.

Distortion: All Outputs at +4 out, .03%, at +22, .09% Max

Gain Range: 150 Ohms Input 10 dB Min., 65 dB Max (inc. PAD).
Un-Bal. Input 14 dB Min., 50 dB Max

VU Meter: Calibrated for XLR Outputs, OVU=+4 dBu, (-12, -6,
-3, 0, +3, +6, +18)

Controls: GAIN, PAD (20 dB), 48Volts, POL (polarity),
MIC (mic/un-ba;), VU, AC

Power Consumption, Quiescent: 19.2 Watts

Size: 19″ X 1.75″ (1U) X 11″ Deep


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