The ITI MEP-230 was one of the very first commercially available parametric equalisers, representing a major step forward in professional audio signal processing. Developed under the direction of George Massenburg and Burgess Macneal at International Telecomm Inc. (ITI), the ITI MEP-230 embodied Massenburg’s new theory of parametric equalisation, providing fully variable control of frequency, bandwidth, and amplitude. Introduced around 1971, the MEP-230 bridged the gap between prototype units such as the ITI ME-230 and the later Sontec mastering equalisers that would become industry benchmarks.
Constructed with discrete circuitry and epoxy-potted amplifier blocks, the ITI MEP-230 offered precision and flexibility unmatched at the time. Each of its three fully parametric bands allowed engineers to sweep through overlapping frequency ranges, control Q (bandwidth), and apply up to ±12dB of boost or cut. In addition to these three bands, the unit provided fixed high and low shelving sections, selectable at 10kHz for high frequencies and at either 50Hz or 100Hz for low frequencies, giving engineers comprehensive tonal control across the entire spectrum.
Unlike earlier passive EQ designs, the ITI MEP-230’s all-active topology used high-quality operational amplifier stages rather than inductors, enabling clean and stable performance without phase shift artefacts. Its design introduced a level of accuracy that was revolutionary for the early 1970s, making it suitable for both recording and mastering applications. Due to limited production and the high cost of manufacture, only a small number of units were made, and each one was hand-assembled to order.
The ITI MEP-230 established the core architecture that would define modern equalisation for decades to come. It directly influenced later Sontec and GML designs, both of which refined and expanded upon Massenburg’s original circuitry. Today, surviving ITI MEP-230 units are prized by collectors and mastering engineers not only for their historical significance but also for their exceptionally musical sound and engineering precision.
Features
- Three fully parametric bands with independent frequency, gain, and bandwidth control
- Fixed high shelf at approximately 10kHz
- Selectable low shelf at 50Hz or 100Hz
- Continuously variable controls for precise adjustment
- ±12dB of boost or cut per band
- Overlapping frequency ranges for wide flexibility
- Discrete active circuitry using custom op-amp modules
- Epoxy-potted internal amplifier blocks for stability and protection
- Rack-mount design with robust construction
- Dual-channel configuration suitable for stereo operation