Three Band Equalizer with Knobs-Terminals

The RDL RU-EQ3 is a three-band audio equalizer designed for line-level signal shaping with user-accessible knob adjustments and terminal connections. Its three defined bands support custom-tailored audio bandwidth, while its high-density rack-mount format provides convenient system integration. The circuit is specified for low noise and low distortion, and an overload indicator flashes whenever either the input or output stage clips.

Ideal Use Cases

The RU-EQ3 fits audio paths that need direct access to low-, mid-, and high-band equalization. It is suited to line-level applications where the source may be balanced or unbalanced and where a 100 kΩ bridging input is appropriate. Its user-accessible knobs place tonal adjustments within reach during operation. The rack-mount-oriented, high-density design also supports installations where equipment space and organized access matter.

Why Choose This Model

This model combines a focused three-band control layout with measured audio performance. The specified center frequencies are 80 Hz for the low band, 1 kHz for the mid band, and 30 kHz for the high band. Each band also has a stated operating bandwidth: 20 Hz to 300 Hz, 200 Hz to 7 kHz, and 3 kHz to 30 kHz, respectively. This arrangement provides three defined regions for shaping a line-level signal. The overload indicator provides a visible warning when the input or output stage clips.

Installation and Integration

The input is 100 kΩ balanced or unbalanced bridging and accepts line-level signals, allowing the equalizer to work with either supported signal configuration. Power is ground-referenced 24 Vdc at 25 mA. A power supply is not included; the listed recommendations are the PS-24AS for the USA and PS-24AX for international use. The specified ambient operating range is 0° C to 55° C. Terminal connections and high-density rack-mount convenience support organized installation, while the accessible knobs keep equalization adjustments available after integration.

Performance Highlights

With the equalizer set flat, frequency response is 20 Hz to 22 kHz within ±0.5 dB into 600 Ω, or 10 Hz to 22 kHz within ±0.5 dB into 10 kΩ. THD+N is specified below 0.030%, with 0.010% typical at 1 kHz using a +4 dBu reference and flat response. Noise is below -80 dB relative to +4 dBu, and common-mode rejection is greater than 60 dB at 100 Hz. Together, these published values document the RU-EQ3’s response, distortion, noise, and rejection performance under the stated test conditions.

What Makes It Different

The RU-EQ3 concentrates on a specific task: three-band equalization with physical, user-accessible controls. The combination of tailored band ranges, a line-level balanced or unbalanced bridging input, terminal connections, and high-density rack-mount convenience defines its role. Its high band extends from 3 kHz to 30 kHz and is centered at 30 kHz, while the mid and low bands cover their separately specified regions. The overload indicator adds a clear warning whenever clipping occurs in either monitored signal stage.

Final Assessment

For systems requiring a rack-oriented three-band equalizer, the RU-EQ3 offers documented line-level input compatibility, accessible knob control, and clearly specified band coverage. Its flat-response measurements, low published noise, low THD+N, and clipping indication provide concrete criteria for evaluating system fit. Confirm the required 24 Vdc power arrangement and select the applicable recommended supply separately, since a power supply is not included.