The Lexicon Prime Time Model 93 Digital Delay was a sophisticated digital delay system designed around a high-performance delay line, extensive special effects capabilities and highly flexible signal mixing. At its core, the Lexicon Prime Time Model 93 used digital delay circuitry derived from Lexicon’s professional DELTA-T series Model 92, with the key advantage of expanded delay capacity. The standard Lexicon Prime Time Model 93 provided over a quarter of a second of delay at full bandwidth, while optional memory extension allowed more than 2 seconds of delay at reduced bandwidth.
The Lexicon Prime Time Model 93 was built for far more than simple echo. Its feature set included a delay time modulator using a voltage controlled oscillator, feedback equalisation, phase inversion, repeat-hold, multiple inputs and outputs, and separate four-function input and output mixers. This gave the Lexicon Prime Time Model 93 the ability to perform reverberation enhancement, distant echo, flanging, Doppler-style pitch shifting, musical vibrato, discordant resonance and a broad range of other time-delay based effects.
Delay selection on the Lexicon Prime Time Model 93 was handled by two delay selectors, A and B, each offering one of 60 possible delay settings displayed in milliseconds. When a selected delay value was a prime number, the prime indicator illuminated. In a standard unit, maximum delay occurred at the 128 ms position, while models fitted with optional memory allowed seven additional positions up to 256 ms. Without optional memory, attempting to use settings beyond 128 ms produced an overrange indication through a decimal point in front of the displayed delay time, with the actual delay remaining at 128 ms.
The Lexicon Prime Time Model 93 also included a Delay Multiply switch, allowing the indicated delay settings to be multiplied by factors of 2, 4 or 8. This extended standard delay times up to 1.024 seconds, or up to 2.048 seconds in units fitted with optional memory. The Delay Multiply positions also changed the system bandwidth, with the 12 kHz bandwidth available at 1x reducing to 6 kHz at 2x, 3 kHz at 4x and 1.5 kHz at 8x.
Beyond stepped delay selection, the Lexicon Prime Time Model 93 allowed continuously variable delay adjustment using the Delay Adjust control. This could reduce the displayed delay value down to 50 percent of that value, such as adjusting 128 ms down to 64 ms. With optional memory, a maximum sweep range of 1 second was possible. Uncalibrated delay settings made through Delay Adjust were indicated by an UNCAL light in the display window. With the Delay Adjust control in the detented cal position, the Lexicon Prime Time Model 93 locked to an accurate crystal time base for the actual indicated delay time.
The input mixing system supplied the signal to the digital delay processor and consisted of four independently adjustable functions with a Master control. These four functions were the main input, auxiliary input and the two delay taps, A and B. The delay taps could be recirculated through variable 6 dB per octave rolloff filters, adjusting the high end rolloff frequency from 15 kHz down to 800 Hz. A five-LED Headroom indicator monitored peak signal levels from 40 dB below limit to 0 dB limit, helping optimise levels through the Input Mix Master, which provided up to 6 dB of gain and up to 25 dB of attenuation.
The output mixing system blended the input, auxiliary input, Delay A and Delay B taps to the Master Output. Its Master control provided from zero to infinite attenuation, while the Overload indicator warned when the output stage was in danger of overload. The overload function indicated the levels of the four mixer functions only and was not affected by the Master control. Input, Delay A and Delay B functions could also be inverted using their respective Phase Invert switches before the Output Mix, with the same switches determining the phase of the recirculated delays back into the Input Mix.
The voltage controlled oscillator section added continuously variable delay modulation whenever the Delay Adjust control was moved out of its counterclockwise cal detent. The UNCAL indicator lit when the Lexicon Prime Time Model 93 entered VCO mode, reminding the user that the indicated delay times were no longer accurate. In this mode, delay time became a function of VCO frequency and could vary across a 2:1 range, sweeping from the indicated delay setting down to half of the indicated setting. The VCO could be controlled manually through Delay Adjust, externally by potentiometer or voltage, or modulated internally by a triangle function generator.
The VCO’s triangle waveform frequency was set by the Frequency control, adjustable from 0.1 Hz to 20 Hz, while modulation amplitude was set by the Depth control. The Depth control panned between the manual Delay Adjust and the internal triangle generator, allowing fully manual control, fully generated modulation or a mix of the two. The VCO was designed so that waveform excursion would remain within the correct operating range, with the level shifting toward the middle when needed. It did not alter signal bandwidth and did not introduce aliasing problems.
The Lexicon Prime Time Model 93 also included Delay Bypass and Repeat Hold functions. Delay Bypass routed the output of the Input Mix directly to the Output Mix Master, bypassing the delay electronics and disabling the Output Mix and Recirculate functions. Repeat Hold repeated an audio segment indefinitely without degradation, using the audio entered into the delay line just before pressing the Repeat Hold button. Pressing the button again deactivated the function and output the contents of the delay line to make room for new input. While active, Repeat Hold blocked additional input to the delay line memory, preventing further delay processing, including delay recirculation.
Repeat Hold segment length was determined by the Delay Multiply setting, VCO settings and the maximum displayed delay setting. In calibrated delay mode with VCO off, the standard memory produced segment lengths of 128 ms at 1x, 256 ms at 2x, 512 ms at 4x and 1024 ms at 8x. With optional memory, these increased to 256 ms, 512 ms, 1024 ms and 2048 ms respectively. Changing the Delay Multiply setting while Repeat Hold was active altered both segment length and octave-related pitch. VCO changes also varied segment length and pitch.
The rear panel of the Lexicon Prime Time Model 93 provided main and auxiliary balanced inputs, each with a switch for either 0 dB or 20 dB of input gain. The 0 dB position accommodated peak levels from +1.3 dBm to +18 dBm, while the 20 dB position accommodated peak levels from -18 dBm to +1.3 dBm, giving a 36 dB input range. The Master Output was transformer-coupled and balanced, delivering up to +18 dBm into 600 ohms as set by the Output Mix Master. Additional outputs included the Input Mixer Out, Delay A Output and Delay B Output. These outputs were single-ended and could also drive 600 ohm loads.
The Lexicon Prime Time Model 93 also supported external control through rear panel jacks. Delay Bypass could be activated by a closure to ground, external delay adjustment could be achieved through a 50k ohm potentiometer or 0 to 10V source connected to the External Delay jack, and Repeat Hold could be enabled or disabled by a normally open momentary switch connected to the Repeat Hold jack.
The Lexicon Prime Time Model 93 was a highly flexible digital delay processor with expanded delay memory options, two independent delay taps, modulation, recirculated filtering, phase inversion, repeat hold and comprehensive input and output mixing. Its design placed it firmly beyond conventional echo duties, making it a programmable-style effects instrument for delay, modulation, pitch movement, resonance and controlled time-based processing.
Features
- Professional digital delay circuitry derived from the Lexicon DELTA-T series Model 92
- Two individually selectable delay taps with 60 settings each
- Digital display of delay time in milliseconds
- Prime indicator for prime number delay settings
- Standard delay capacity of 128 ms at full bandwidth
- Optional memory support for 256 ms at full bandwidth and up to 2048 ms with Delay Multiply
- Delay Multiply settings of 1x, 2x, 4x and 8x
- Bandwidth automatically changes with Delay Multiply settings
- Continuously adjustable Delay Adjust control
- Crystal time base in calibrated delay mode
- Voltage controlled oscillator for delay modulation
- Internal triangle function generator
- VCO frequency adjustable from 0.1 Hz to 20 Hz
- Depth control for blending manual delay adjustment and modulation generator control
- Repeat Hold function for indefinite repetition without degradation
- Delay Bypass function with indicator
- Independent Input Mix and Output Mix sections
- Four-function input and output mixing
- Recirculated delay rolloff filters from 15 kHz to 800 Hz
- Phase inversion for input and delay functions
- Five-LED Headroom indicator
- Overload indicator for output mixer functions
- Balanced main and auxiliary inputs
- Transformer-coupled balanced master output
- Additional single-ended outputs for Input Mix, Delay A and Delay B
- External control of Delay Bypass, Delay Adjust and Repeat Hold