Parasound 622B Parametric Equaliser

Two channels of overlapping four-band parametric EQ with a constant-Q curve — the box that ended up in more studio racks than anyone can count.

Overview

The 622B is a two-channel parametric equaliser with four continuously variable bands per channel, and its tuning ranges overlap deliberately: the low-frequency band sweeps 20–500 Hz, the low-mid 68 Hz–1.7 kHz, the high-mid 240 Hz–5.85 kHz, and the high band 800 Hz–20 kHz. That overlap is the whole point. You can stack two sections on the same problem frequency and carve a narrow notch, or spread them out and shape a broad musical curve. Each section's Q is variable between 0.29 and 3.2, so a single band can go from a gentle shelf-like nudge to a surgical cut without swapping modules.

The control range is unusual and worth spelling out: +16 dB of boost down to infinite attenuation, with a typical obtainable notch depth of around 40 dB. That asymmetry is a giveaway about the design intent. This is an equaliser built to subtract. The 622B's constant-Q behaviour — rather than the reciprocal curves common on cheaper parametrics — means the bandwidth stays put as you crank the cut, so a notch stays a notch instead of widening into a vague scoop.

Noise performance is solid for the period: the published figure is less than −84 dBm at the output for unity gain with the EQ in and the controls flat. That's the kind of number that matters when you're chaining a dozen outboard pieces across a console — the 622B doesn't add hiss to the stack. It's a working tool, not a hi-fi ornament, and it was priced accordingly. The two-channel version listed at $695, per the Studio Sound (February 1978, p.48) equaliser survey.

The 622B was the successor to the Orban 621B stereo parametric, and the revision brought real ergonomic improvements rather than cosmetic ones. Studio Sound (September 1977, p.14) reported that the new model added individual in/out switching for each band, an internal power supply, and a lower cost than the unit it replaced — three changes that all point the same direction: less fiddling, fewer wall warts, easier to justify buying several.

The constant-Q curves mean the EQ does what the knob says, and the click-free in/out switching and LED overload indication make it safe to use live. It's the sort of box an engineer reaches for without thinking, which is the highest compliment outboard gear can get.

But for anyone building a rack of period outboard, the 622B is one of the more sensible purchases you can make: it does one job, does it well, and doesn't ask for much in return.