AH124
The AH124 is a variable-mu tube compressor inspired by the extremely rare EMI RS124, used in EMI studios around the world, including Abbey Road. The RS124 originated from Altec 436B units acquired in the late 1950s and subsequently modified by EMI engineers to meet the demands of their studios.
These units gave rise to the legendary EMI RS124s, widely used in the 1960s and 1970s, a period when artists like the Beatles and Pink Floyd recorded historic albums at Abbey Road.
Our version of this classic features some modifications to enhance its versatility and ease of use in modern studios, such as:
- Boost switch that injects more signal into the input transformer. This makes the compressor work more aggressively. The Boost switch injects an additional 15dB into the compressor, bringing a more colorful and saturated sound to the unit.
- High Pass filter on the sidechain, making the compressor act on frequencies above 150 Hz.
- Attack and Recovery controls with 6 different positions, controlled by a rotary switch. On the Attack switch, positions 2 and 3 correspond to the fixed times of the EMI RS124 and the Altec 436B, respectively.
- Input transformer with Mu-Metal shielding developed and manufactured by Analog Heroes, which prevents any type of interference or noise caused by radio frequencies.
- Bypass switch, which facilitates the comparison of the uncompressed signal with the signal passing through the AH 124.
- Use of modern, high-quality tubes, selected for Hi-Fi audio and tested.
- Polyester capacitors and high-precision VU meter.
The AH124, like several other variable-mu compressors, operates with a fixed Threshold, meaning that the compression level is defined by the amount of signal injected into the compressor, controlled by the Input potentiometer.
O AH124 é o compressor varimu mais versátil que já usei.
O AH 124 é mágico! Melhora o timbre de tudo que passa por ele. Às vezes nem uso a compressão, só passo pelos harmônicos da válvula.
TRANSFORMERS
The AH124 features an oversized input transformer, housed in a dedicated Mu-Metal shielded enclosure, designed to minimize electromagnetic interference and radio frequency noise. This solution ensures operational silence and preserves the compressor's sonic character.
DESIGN AND CONSTRUCTION
The entire mechanical assembly is developed by Analog Heroes. The robust chassis was designed to safely house the tube circuit and transformers, ensuring durability, thermal stability, and reliability for continuous studio use.
MANUAL ASSEMBLY
Each AH124 is hand-assembled in our lab, following a careful process of assembly, testing, and calibration. The units are produced in small batches, ensuring rigorous quality control and consistent performance, in line with the philosophy of classic variable-mu compressors.
The RS124 was born out of EMI engineers' dissatisfaction with an Altec 436B compressor imported from the United States. In 1959, Bill Livy, Len Page, and Mike Batchelor redesigned the equipment, creating a new device.
No two units were exactly alike: constant adjustments to components resulted in distinct sound qualities and response times, making each piece more suitable for a specific function, whether tracking, bus processing, or mastering. Only about 25 units were produced, and few have survived.
Geoff Emerick used the RS124 to give weight to basses, Ken Scott to enrich guitars, and Norman Smith to tie the rhythm section together. At Abbey Road, it was common to force gain reductions between 15 and 20 dB, which generated dense and full-bodied textures.
After years of obscurity, the RS124s have returned to use, and modern engineers have rediscovered their charm, considering the 1959 design equivalent to or superior to many current pieces of equipment.
AH124
Specifications
Compressor with variable-mu topology (tube).
Variable-Mu (Valvulado)
600 Ohms / 600 Ohms
20Hz to 20kHz
48.2cm x 28cm x 9cm 2RU
12.57 lbs