FM "Utility" Processor

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The Model 260 satisfies basic processing needs in educational FM, TV sound and similar set-and-forget applications. Final limiting is performed in a split-band arrangement to protect the transmission pre-emphasis characteristic.

User controls are restricted to input and output level adjustments; there are no controls affecting the "sound" of the processor.

The 260 supplies comprehensive processing, or any of the functions may be defeated with jumpers on the rear panel. This allows the 260 to serve as an AGC-only, a peak controller-only, etc.


  • Gated AGC and compression; programcontrolled ‘floating platform’ limiter release characteristic.

  • Feedforward pulse-width-modulation (PWM) audio processing for a very smooth sound devoid of processing artifacts.

  • Unique level alarm warns of ‘dead air’ and out-of-limits operation.



Frequency Response

±0.5dB, 10Hz-15kHz


Better than 75dB below 100%-modulation output level, 10Hz-15kHz

Distortion (With full AGC correction and 10dB dynamic reduction)

<0.5%THD, 20Hz-15kHz; <0.25%THD, 50Hz-10kHz


Better than –60dB, 10Hz-10kHz

Program Line Inputs

(L/R) Active-balanced, bridging; accept program audio levels between –20dBu and +10dBu.

Program Line Outputs

(L/R) Active-balanced, 600-ohm source impedance; deliver 0dBm to +15dBm into 600-ohm loads.

Gate Circuit

Gating inhibits AGC ‘hunting’ and compression release during brief pauses in the input program. Extended program loss slowly returns circuit gains to resting values.

AGC Amplifier

Slow-AGC erases long-term program level variations for more consistent compression and limiting action. AGC may be independently defeated by grounding a rear-panel terminal. Correction range: ±12dB; correction rate: 0.5dB/sec

Dynamic Reduction

Compression and limiting share a common split-spectrum gain control circuit. The two functions are separated by a time-domain “floating platform” attack/release characteristic. Compression or total dynamic reduction may be independently defeated by grounding rear-panel terminals.

Spectrum Division

Independent high frequency gain reduction follows the 75µs pre-emphasis characteristic. (50µs optionally available.)

Safety Clipper

Active only on limiter overshoots that would exceed 100% modulation. Conforms to pre-emphasis characteristic.

Level Alarm

Front-panel indicator flashes when AGC correction exceeds ±9dB, or when “dead air” exceeds 10 seconds.

Power Requirements

105-130VAC or 210-255VAC, 50/60Hz; 20W

Size and Weight

1-3/ 4”H x 19”W x 8”D (1U); 12 lbs.