Lexicon Model 97 Super Prime Time
Forty memory registers, two delay lines, and a foot pedal input - the rack unit that let a guitarist store a flanged, chorused, slapbacked patch and call it back mid-set.
Overview
The Model 97 "Super Prime Time" is a microprocessor-controlled digital delay and effects processor. Lexicon's own manual opens by calling it "a major advancement in digital audio equipment." The spec sheet backs that up. The standard unit offers a maximum delay time of 480 milliseconds, and memory extension options push that to either 960 milliseconds or 1.92 seconds, all at full 20 kHz bandwidth.
That last detail is the big one. Plenty of early digital delays traded bandwidth for delay time, and the Model 97 doesn't. The manual's noise-test procedure shows what the designers were after. With all sliders down and the unit bypassed, the master output is expected to sit below -78 dBm, the main source input below -75 dBm, and the auxiliary input below -70 dBm. Engage the +20 dB gain switch and the noise floor rises to below -67 dBm. That's the price of the extra headroom, and Lexicon printed the number openly.
Two separate inputs provide versatile mixing and allow cross-connection of two delay lines for stereo or for complex processing. Separate input mix, output mix, and delay-only outputs are provided. The manual claims that one Model 97 can do the job of a dozen conventional signal processing units. The main audio chain runs through digital control, and the front panel is dense with sliders, rotary pots, and amber seven-segment LED time displays for the A and B delay taps.
Connectivity was clearly designed for a working studio rather than a home rack. Standard phone jacks and balanced XLR connectors are provided, plus a 20 dB input gain boost switch for low-level sources such as electric guitars or -10 dBV to -20 dBV line level equipment. The main input XLR and tip/ring/sleeve phone jack are balanced and wired in parallel. Nominal sensitivity is 0 dBV, and pressing the gain button raises that by 20 dB so that -20 dBV signals will drive the unit to "0" VU input level with sliders at maximum positions. On the output side, the XLR is electronically balanced with the phone jack in parallel, both carrying the combined delay and direct signals from the output mix section. Output source impedance is an actual 200 ohms, intended for use with 600 ohm or higher impedance inputs, with a maximum output level of +22 dBV. To drive a single-ended load, the manual notes, the XLR pin 3 or the phone jack ring must be tied to ground - preferably at the load end of the cable for minimum noise.
There are a total of 40 storage registers, 32 of which are user programmable and 8 of which are factory preset. The presets are typical versions of flanging, resonant flanging, doubling, tripling, chorusing, slap echo, short echo and long echo. Players can use them raw or modify them to create and store customized effects. The manual pitches this at the performing musician who needs to work out special effects prior to the show or recording session and then have them instantly available, and at the busy recording engineer who needs to change delay effects with split-second timing.
Saving patches to tape is handled by the TAPE STORE OUT jack, an unbalanced line-level output at 0 dBV nominal, suitable for cassette or reel-to-reel recorders. Only the appropriate frequency-shift keyed digital data written with this or any Model 97 will be recognized as valid input, and the jack also outputs cue tones on tape for automatic stepping through the memory registers upon playback — a clever bit of 1980s workflow that predates MIDI patch dumping in this corner of the market.
Modulation and remote control get their own jacks. The MODULATION IN tip/ring/sleeve phone jack is normalled to the MODULATION OUT jack, so with no plug inserted the internal LFO routes to change the delay time. Insert a plug and an external 0 to +10 V source can take over the VCO instead. The RATE IN jack is intended for a foot pedal or rotary pot and provides remote control of the LFO rate. An external 0 to +10 V DC across tip and sleeve changes the LFO rate from 0.05 Hz to 5 Hz, provided the front panel RATE control is set to 5 Hz - 5 Hz to 500 Hz if in X100 mode. If the RATE control isn't at maximum, the external effect scales down accordingly. The Model 97 supplies its own +10 V DC to the ring of the RATE IN jack, so a Lexicon foot pedal, or any control using a 50 kilohm pot, can be wired in directly. Three further jacks rely on external switch closures and operate on low, logic-level voltages of 3 to 5 V DC.
Studio Sound (March 1982, p.32) covered the Super Prime Time as a new product developed from the well-respected Prime Time, noting the input mixing and the facility to cross-link two delay lines for stereo or complex signal processing. A full review by Hugh Ford followed in Studio Sound (January 1984, p.80). The manufacturer's specification it listed gave frequency response as 20 Hz to 15 kHz, ±1 dB at x1, with rotary controls for Delay Taps A and B and large amber seven-segment digital LED time displays. The same issue's measurement write-up noted the response was shown to be flat within the audio band at any gain setting, with intermodulation distortion tested to the twin-tone CCIF method.
Power handling is straightforward but worth knowing before buying one. Normal operating line voltages are 100V, 120V, 220V, or 240V, all within ±10% of nominal, and the correct voltage is printed on a label on the rear panel as shipped. Current draw should stay below 0.4 A for 100/120 V and below 0.2 A for 220/240 V. The internal supply rails are unusual in one respect: the +12 and -12 V supplies were optional and only installed in early units — they are not used. There's also a battery-backed +3.6 V rail, spec'd at 3.60 to 4.20 V, which is what keeps memory alive between sessions. Anyone servicing a Model 97 should expect that battery to be the first thing to check when patches stop surviving a power cycle.
At 87% of line voltage the NMI/ line should go high, and the manual specifies an adjustment procedure via R8 on the digital board. NMI/ goes low at about 75% of line voltage. On power-up at nominal line, RST/ should go high 150 ms (±50 ms) after NMI/. The mute line goes low 500 ms (±100 ms) after NMI/ goes high. The manual is explicit that the unit should power down abruptly and cleanly and power up free of any thumps across all four outputs - A-DLY, B-DLY, INPUT MIX, and MASTER.
The electronically balanced output circuit requires a special test cable for calibration, with R1 and R2 above 20 kilohms and precisely matched. With a 1 kHz input at 12 dBm, differential output should verify below -50 dBv. Switch to 10 kHz and it should hold below -40 dBv. If those readings aren't met, R57 is adjusted for a null at the differential output and the test repeated. Delay times are verified with a pulse generator and oscilloscope - or, for noncritical testing, simply by listening to the various delay settings.
For buyers today, the practical questions are the battery, the fuse ratings, and whether the memory extension options are already installed. US and Canadian units take 1/4" diameter x 1-1/4" long primary fuses. Export models take 5 mm diameter x 20 mm long fuses, with internal secondary fuses at 20 mm. Lexicon's warning is the usual one: replace fuses only with identical current ratings. The 480 ms standard delay is the baseline. A unit advertised with 960 ms or 1.92 seconds has been optioned, and that's worth confirming against the serial rather than taking a seller's word for it.
What the Model 97 represents, more than anything, is the moment digital effects stopped being single-trick devices. Forty registers, two cross-linkable delay lines, external modulation and rate control, tape dump, and a foot-pedal input on a rack unit — that's a workstation's worth of routing in a box the manual describes as doing the job of a dozen conventional processors. Whether it does that job by modern standards is a different question. Whether it did in 1982 is not.
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