Orban 764B Programmable Parametric Equalizer

A four-band parametric with 99 memory registers, no VCAs in the audio path, and a filter that changes its own character as you sweep it.

Overview

The 764B is a stereo four-band parametric equalizer with digital control over every parameter — and the spec that tells you Orban was serious about the audio path is the one about what isn't there. The company's own catalog copy for the unit makes a point of the "high-quality, no-compromise audio path having no VCA's," which is the kind of claim that separates a studio tool from a digitally-controlled convenience box. Plenty of programmable EQs of the era put voltage-controlled amplifiers in the signal path and lived with the noise and distortion; Orban built the 764B without them.

Each of the four bands offers overlapping tuning across a 25:1 frequency range, with +16 dB of boost and -40 dB of cut available per band. Bandwidth is variable from 5 octaves down to 0.1 octaves — a Q range of 0.3 to 15 — and the company's "Constant-Q" design is what lets the thing double as a genuine notch filter rather than a broad shaping tool that only pretends to be one. Orban's literature is explicit that the constant-Q topology allows the equalizer to be used as a true narrowband notch filter, a broadband shaping equalizer, or both at once.

Then there are the filters, which are the part collectors tend to bring up first. A continuously-variable 18 dB/octave third-order Butterworth high-pass sits alongside a 12 dB/octave low-pass that Orban called "Automatic Sliding Besselworth" — a proprietary design that shifts smoothly from a musical Bessel characteristic toward a sharper Butterworth response as the cutoff frequency climbs. The stated goal was a filter that strips the maximum unwanted noise while sidestepping harshness. Whether it fully delivers is a judgment call, but it's a genuinely unusual piece of engineering for a rack EQ.

The programmability is the headline, though. All four bands, both filter cutoff frequencies, input gain, and the stereo/dual-mono status can be stored in any of 99 non-volatile memory registers. A complete two-channel setup saves with a three-keystroke sequence on the keypad, and digital and LED displays show the current value of whatever parameter is being adjusted. Recall happens manually, over MIDI, or through the serial interfaces. An internal lithium battery holds memory through power failures for up to five years, and a security lockout code keeps unauthorized hands off stored curves — a feature clearly aimed at installed-sound contractors who need a room curve to survive the client's nephew.

The expansion story is where the 764B gets interesting for studio people. Up to 14 two-channel slave units can be addressed by the master, giving as many as 28 independent channels or 14 stereo pairs under one controller. Each pair can be ganged to track in stereo or programmed independently. Orban pitched this directly at consoles: a stack of slaves under a 764B master, in the company's words, brings a high-quality desk "closer to the capability of multi-hundred thousand dollar consoles." That's marketing copy, not a measured verdict — but the architecture it describes is real.

MIDI control was an option, and the remote port accepts contact-closure pulses to call stored setups in sequence. A serial interface was planned as a field-installable option, and the trade press of the period noted the 764B could be ordered with RS-422, RS-232, and MIDI interfaces. Mix (1988, p.87) covered the unit in its preview pages, describing the overlapping tuning and 25:1 range that Orban's own literature also cites. Studio Sound (January 1990, p.21) ran the 764B alongside Orban's RX processor, noting the 99 memory locations and the three-knob parameter adjustment — a useful confirmation from an independent British publication that the memory count and control scheme were as advertised.

The applications Orban laid out read like a tour of late-'80s professional audio. Multi-track tracking and mixdown, where repeatable EQ setups save a session from being rebuilt by ear every morning. Video and film post, where a SMPTE-to-MIDI converter lets an entire production's EQ changes be recalled by timecode, and where ADR "personality settings" for regular talent can be stored for consistency. Installed sound and touring, where a house curve gets locked down and recalled per venue. And disc and CD mastering, where the master unit handles the program channel and a slave covers preview, with EQ for the whole disc pre-programmed and pulled up as needed. Orban's copy also takes a swipe at the competition here, arguing that the full-parametric/notch capability offers advantages over traditional 1/3-octave graphics while avoiding the phase shift and ringing those graphics tend to introduce.

What the documentation doesn't settle is the basics collectors want first: production years and original price aren't established in the available material, and no independent bench measurements turned up in the period chunks. The unit appears in trade coverage from 1988 through 1990, which brackets its market presence without pinning down a run. Anyone chasing a 764B should verify the optional interface cards are actually installed — the MIDI and serial options were just that, options — and should confirm the internal lithium battery hasn't gone flat, since a dead cell takes the 99 registers with it. The no-VCA audio path and the sliding filter design are the reasons to seek one out; the memory battery and the option-card scavenger hunt are the reasons to inspect before buying.