Acme Audio Motown EQ

Acme Audio Motown EQ recreates the seven-band graphic equalizer designed by Motown Records chief engineer Mike McLean. Only forty-eight originals were ever built. Acme Audio spent several weeks taking one apart under McLean's own guidance.

Stepped control instead of faders

Rather than sliders the unit uses rotary switches, and each band tops out at 8 dB. That sounds modest until you put it on bass or a horn section: the passive inductor circuit shapes the band gently and without phase artefacts, so 3 dB here does more than 6 dB on a typical digital equalizer.

Period-correct parts, not close approximations

Inductors are wound by Mesanovic on MPP cores, the input transformer is an AMI A24, the output transformer is custom made, and the output stage is built around an Opamp Labs 425 amplifier. Values and tolerances follow the original rather than modern equivalents with similar figures on paper. The power supply sits outside the chassis, which lowers the noise floor. Response reaches from 10 Hz to 30 kHz within 1 dB.

KEY FEATURES

• Seven-band passive graphic equalizer on rotary switches
• Recreation of Mike McLean's design for Motown Records
• Mesanovic inductors on MPP cores
• AMI A24 input transformer and custom output transformer
• Opamp Labs 425 output amplifier
• External power supply for a lower noise floor
• 19 inch, 2U aluminium rack chassis

TECHNICAL SPECIFICATIONS

• Type: passive graphic equalizer, seven bands
• Frequencies: 50 Hz, 130 Hz, 320 Hz, 800 Hz, 2 kHz, 5 kHz, 12.5 kHz
• Range: +/- 8 dB
• Frequency response: 10 Hz - 30 kHz, +/- 1 dB
• Maximum level: 29 dB
• Input transformer: AMI A24
• Output transformer: custom made by Mesanovic
• Output amplifier: Opamp Labs 425
• Connectors: XLR input and output
• Channels: 1
• Format: 19 inch rackmount, 2U, aluminium chassis
• Power: external power supply included