The Urei 565 “Little Dipper” filter set combines computer aided active filter design with space-age integrated circuitry. Only 51/4″ high, the Model 565 provides FOUR separate, continuously tunable cascaded filters:
- An 18 dB per octave Low Cutoff Filter, tunable from 20 Hz to 200 Hz.
- TWO band reject (dip) filters, with 50 dB minimum rejection and variable notch width to as Sharp as 5% of Center frequency; each continuously tunable from 20 Hz to 20 kHz. Or,
- Both band filters may be optionally switched to become band PASS filters – each continuously tunable 20 Hz to 20 kHz.
- An 18 dB per octave High Cutoff Filter, tunable from 2 kHz to 20 kHz.
The Urei 565 is completely self-contained (operates from 110-120 V.A.C. or 220-240 V.A.C., 50/60 Hz) and is designed for no-loss insertion in program circuits. A switch is provided to optimise performance in either -20 dBm or O dBm nominal level environments. While the Little Dipper’s versatility makes it an ideal tool for many signal processing tasks, its primary function is to remove undesirable “coherent” or “semi-coherent” noise components from audible range recorded tapes, film or records.
For example, AC hum, oscillations, heterodyne ‘whistles,” etc., can be rendered completely inaudible with no apparent effect on the sound quality of music or voice, because Of the extreme sharpness of the band reject characteristic. Semi-coherent sounds, such as camera noise or fluorescent fixture “buzz” can be greatly reduced.
Sounds of an incoherent nature such as jet aircraft, amplifier noise, and general background noise can be effectively reduced using the Low Cutoff and High Cutoff filters with or without the band reject filters. A silent operating “bypass” switch is provided on the front panel to add or remove all filter action instantly at will.
The Urei 565 can be used effectively for:
- SPECIAL EFFECTS. The notch filters can be used to produce “Phasing” effects. A double phasing effect may be achieved by using both notch filters simultaneously.
- ENHANCEMENT. Extremely sharp enhancement of any frequency or any two frequencies in the audio spectrum is possible in this mode. Combinations of high cutoff, low cutoff, band pass and notch with variable frequency can be used for imaginative creative effects.
- HARMONIC DISTORTION FILTER. The very low distortion of the Urei 565 and its deep notch allows its use as a distortion measurement filter. The fundamental of any frequency from 20 Hz to 20 kHz may be removed for total harmonic measurement.
- HARMONIC WAVE ANALYSIS. The individua’ harmonics of complex audio waves may be selected using the bandpass filter, allowing exact harmonic structure analysis.
Urei 565 Filters
- Low Cutoff Filter
- Slope: 18 dB/octave (60 dB/decade)
- Frequency Range: 3 dB down point continuously tunable from 20 Hz to 200 Hz
- Control: Tuning dial, 20 Hz to 200 Hz
- High Cutoff Filter
- Slope: 18 dB/octave (60 dB/decade)
- Frequency Range: 3 dB down point continuously tunable from 2 kHz to 20 kHz
- Control: Tuning dial, 2 kHz to 20 kHz
- Notch/Pass Filters (Two in Set)
- Notch Depth: 50 dB minimum
- Frequency Range: Continuously tunable from 20 Hz to 20 kHz
- Notch Width: Selectable 5%, 10%, or 50% of center frequency at 3 dB points
- Band Pass Q: Switch selectable 1.2, 5, or 10
- Band Pass Gain: Unity ±1 dB at peak
- Controls: Frequency dial, frequency multiplier, notch balance, fine frequency vernier, notch width, filter bypass
