The Orban 622 Parametric Equalizer was a professional analogue parametric equaliser designed for demanding studio, broadcast, sound reinforcement, theatre, disco, public address and motion picture sound applications. The Orban 622 Parametric Equalizer was documented in Orban literature dated March 1980 and remained listed in Orban’s professional audio product range in February 1986, with the single-channel Orban 622A listed at $569.00 and the dual-channel Orban 622B listed at $879.00.
The Orban 622 Parametric Equalizer was described as a true parametric equaliser, with continuously variable control over equalisation amount, centre frequency and bandwidth. Unlike quasi-parametric designs, the Orban 622 Parametric Equalizer was designed so that changing one parameter did not alter the others. This made the Orban 622 Parametric Equalizer a precision tool for corrective equalisation, tonal shaping and narrow-band problem solving, where frequency, gain and bandwidth could be adjusted independently.
Each channel of the Orban 622 Parametric Equalizer included four peak boost and cut sections connected in series. Each of the four sections was fully non-interacting, meaning the total equalisation was simply the sum of the individual equalisation sections. Each section included tuning and bandwidth controls, together with an equalisation control and individual in/out switching. The Orban 622 Parametric Equalizer also included a master equalisation in/out switch, front-panel gain control, and power switching.
A major design feature of the Orban 622 Parametric Equalizer was its constant-Q equalisation circuitry. Orban promoted this as more musically useful than reciprocal equalisation curves, with boost curves that remained broad enough for general shaping and cut curves narrow enough for highly selective correction. The constant-Q design also allowed any section of the Orban 622 Parametric Equalizer to be used as a narrow-band notch filter, with typical notch depth better than 40dB. This made the Orban 622 Parametric Equalizer suitable for suppressing fixed-pitch problems such as hum, room resonances and other unwanted tonal components, while causing minimal change to the rest of the programme material.
The Orban 622 Parametric Equalizer offered an equalisation range of +16dB to minus infinity, with Q adjustable from 0.29 to 3.2. Each section tuned over a 25:1 frequency span, with the four bands covering 20Hz to 500Hz, 68Hz to 1.7kHz, 240Hz to 5.85kHz, and 800Hz to 20kHz. The tuning dials were calibrated at ISO preferred frequencies, allowing the Orban 622 Parametric Equalizer to be used for both broad tonal work and precise frequency correction.
In sound reinforcement, the Orban 622 Parametric Equalizer was intended for room tuning, feedback control and loudspeaker system optimisation. The availability of four narrow-band notches per channel made it useful for dealing with sharp resonances, either on its own or alongside third-octave filter sets. In large sound reinforcement systems, Orban highlighted the use of the Orban 622 Parametric Equalizer for stage monitor equalisation and for optimising individual drivers in bi-amped and tri-amped loudspeaker installations.
In recording studios, the Orban 622 Parametric Equalizer was positioned as a tool for equalisation tasks that conventional console EQ could not handle. Orban described it as useful for fine-tuning individual tracks, correcting finished mixes, creating broad non-ringing boosts, and shaping synthesizer sounds with high-Q formants. The ability to create deep notches and broad boosts from the same unit made the Orban 622 Parametric Equalizer more flexible than a fixed-frequency graphic equaliser for many studio applications.
For motion picture sound, the Orban 622 Parametric Equalizer was presented as an alternative to the graphic equaliser normally used for dialogue equalisation. It provided finer control and the ability to remove extraneous location recording problems with narrow notches. Orban also identified production uses such as special effects, telephone-style treatments and old-time recording effects.
In broadcasting, the Orban 622 Parametric Equalizer was aimed at production studios, programme lines, announce microphones, phone lines and remote lines. It could be used to enhance announcer microphones, create production effects, equalise lines for flatter response, add presence, and notch out unwanted noise such as mechanical hum or air conditioning noise. The RFI suppression on the input, output and power leads, together with the optional transformer-balanced output, made the Orban 622 Parametric Equalizer suitable for installation in high-RF broadcast environments.
The technical design of the Orban 622 Parametric Equalizer used a balanced input buffer amplifier, an input attenuator, and four peak/dip equalisation sections connected in series. A final current booster section allowed the output to drive 600-ohm loads. The output of the input buffer and each equalisation section was monitored by the overload indicator, while the EQ in/out switching bypassed all circuitry except the input buffer and output amplifier. This arrangement maintained gain and signal polarity in both the in and out modes.
Equalisation in the Orban 622 Parametric Equalizer was achieved by summing the output of a two-pole bandpass filter with the main signal. For boost, the bandpass output was summed in phase; for cut, it was summed out of phase. As the bandwidth control was adjusted, the skirts of the equalisation curve moved while peak gain stayed constant. As the tuning control was adjusted, the curve moved along the frequency axis without changing shape. Shelving-style curves could be approximated by setting the lowest band to 20Hz and the highest band to 20kHz, then adjusting the breakpoint with the bandwidth control.
The Orban 622 Parametric Equalizer was available in single-channel and dual-channel versions. The Orban 622A was the single-channel model, while the Orban 622B was the two-channel model. Both versions shared the same professional operating concept, with the dual-channel Orban 622B providing two complete channels in a rackmount chassis. The unit used an active balanced input and an unbalanced output as standard, with a transformer-balanced output available as an option.
Orban placed emphasis on ruggedness and professional reliability. The chassis was designed to provide shielding from electrical interference, RFI and dust, while reliability was supported by a formal burn-in programme and additional high-temperature burn-in of most semiconductors. The Orban 622 Parametric Equalizer was also designed for compatibility with professional levels, impedances and connectors, making it suitable for installation into existing professional systems.
The Orban 622 Parametric Equalizer had a frequency response of ±0.25dB from 20Hz to 20kHz with the EQ controls set mechanically flat. It offered +12dB of available gain from the front-panel gain control, total harmonic distortion below 0.025% from 20Hz to 20kHz at +18dBm output, and typical total harmonic distortion below 0.002% at 1kHz and +18dBm. Noise was specified at less than -84dBm, with -87dBm typical, when the gain control was set for unity gain, all EQ switches were in, and all EQ controls were flat.
The Orban 622 Parametric Equalizer also specified a slew rate greater than 6V per microsecond, with internal bandlimiting intended to prevent slew-rate limiting even under severe equalisation and programme material conditions. Orban also specified a square wave response with no spurious ringing at any output level, except for the ringing theoretically associated with a given equalisation curve. The active RC circuitry used FET-input IC operational amplifiers, while the output line driver used a discrete transistor current booster.
The Orban 622 Parametric Equalizer remains notable as a professional constant-Q parametric equaliser that combined corrective precision, musical broad shaping and deep notch filtering in one unit. Its combination of four independent parametric sections per channel, wide tuning ranges, independent control operation, low noise, low distortion, overload indication and professional installation features made it a flexible equalisation tool for studios, broadcasters, live sound systems and film sound facilities.
Features
- True parametric equalisation with independent control of equalisation, tuning and bandwidth
- Constant-Q operation for musically useful boost curves and narrow corrective cut curves
- Four non-interacting peak boost and cut sections per channel
- Each section usable as a narrow-band notch filter
- Typical notch depth better than 40dB
- +16dB to minus infinity equalisation range
- Q adjustable from 0.29 to 3.2
- Each section tunes over a 25:1 frequency span
- Front-panel gain control with 12dB of available gain
- Individual in/out switches for each section
- Master equalisation in/out switching
- Peak-stretching overload indicator monitors overload anywhere in the equaliser
- Active balanced input as standard
- Transformer-balanced output available as an option
- Single-channel and dual-channel models available
- RFI suppression on input, output and power leads
- Designed for sound reinforcement, recording studio, broadcast, motion picture sound, public address, disco and theatre applications
