Notch Filter/Limiter
Vintage UREI Model 562 Feedback Suppressor Rack Mount Unit
5 independently adjustable notch filters. Narrow notches minimize sound coloration. Built in peak clipper for driver protection during setup tuning. High cut and low cut end filters. Headroom indicator monitors signal levels and approach of overload. Bypass switch for easy setup and A-B comparison.
The 562 contains 5 active notch filters, each continu- ously adjustable in notch depth from 0 to 20 dB, and in frequency from 60 Hz to 6000 Hz. Low cut and high cut filters with 12 dB/octave slopes are tunable from 20 to 200 Hz and 2.5 to 20 kHz respectively. The Model 562 has front panel adjustable gain, ranging from Ñ10 to +20 dB and headroom indicators to optimize the signal level. A bypass switch allows A-B comparison, and a setup switch provides system protection during tuning. XLR/QG connectors and terminal strips are provided for both input and output. In using the Feedback Suppressor, the system's gain is slowly increased until the first sustained feedback occurs. One notch filter is then "tunedÕÕ until the feedback ceases. The gain is increased again, and the next reso- nance attenuated with the second filter. This procedure is repeated with filters 3 through 5. If feedback occurs at the extreme high or low end it can be reduced by using the end cut filters. A typical result is an increase of several dB in actual system gain before feedback. In addition intelligibility is improved without undesirable changes in fidelity. SPECIFICATIONS ELECTRICAL: INPUT: Input Impedance: 40 kohms balanced, 20 kohms unbalanced. Maximum input Level: +20 dBu Gain: Variable Ñ10 dB to +20 dB with front panel level control. Headroom Indicator: 4 LED indicators showing maximum signals: 0, Ñ10, Ñ20, Ñ30 dB relative to overload. NOTCH FILTERS Frequency Range Notch Depth Filter Bandwidth 60 Hz to 6 kHz, continuously variable in two ranges. 0 to Ñ20 dB, continuously variable. Approx. 1/6 octave at 5 dB notch depth (3 dB points). END CUT FILTERS Low Cut Filter High Cut Filter 12 dB per octave filter slope, continuously adjustable from 20 Hz to 200 Hz. 12 dB per octave filter slope, continously adjustable from 2.5 kHz to 20 kHz. OUTPUT Output Circuit Output Load Power Output Distortion Frequency Response Output Noise Power Requirements Environment Floating, transformer isolated. 600 ohms or greater. +20 dBm Less than 0.5% THD, 30 Hz to 15 kHz at maximum rated output. ±0.5 dB, 20 Hz to 20 kHz (EQ out). +0.5 dB, -1.5 dB. 20 Hz to 20 kHz (EQ in). Less than Ñ90 dBm ( 15.7 kHz noise bandwidth, input and output terminated with 600 ohms: controls set for unity gain). Less than 10 W, 100-125 V AC or 200-250 V AC. 50/60 Hz. switch selectable.