Rolls MO2020se Test Tone Oscillator / Audio Signal Generator, Sine and Square

Rolls MO2020se: A Portable Sine and Square Wave Test Tone Oscillator

The Rolls MO2020se is a portable audio-frequency signal generator that produces both sine and square waves from 20 Hz to 24 kHz for testing, calibrating, and troubleshooting audio systems. It is a bench and field reference tool, not an audio processor: its job is to inject a known, clean test tone into a signal chain so you can measure what happens to it. Separate XLR, RCA, and 1/4-inch outputs let it connect to professional and consumer test points without adapters, and independent level controls set the sine and square outputs. A switchable 30 dB pad and a VCO control input extend it from simple level-setting to swept-frequency testing. For install technicians, service benches, and anyone who needs to verify an audio system objectively, the MO2020se is a compact, dependable tone source.

Sine and Square Waves From 20 Hz to 24 kHz

The MO2020se generates sine waves and square waves continuously across the full 20 Hz to 24 kHz audio band, with independent level controls for each waveform. A sine wave is the cleanest possible single-frequency reference and is what you use to set levels and measure distortion, while a square wave is rich in harmonics and reveals frequency response and slew behavior in a system. Having both on tap from one box means you can check a speaker at a specific frequency and then square-wave test an amplifier's response without swapping tools. The sine output specifies less than 3 percent THD, clean enough to serve as a working reference. For anyone sweeping a room or verifying a crossover, covering the whole audio band with two waveform types is what makes the MO2020se a complete test source.

XLR, RCA, and 1/4-Inch Outputs

The MO2020se provides the sine wave on XLR, RCA, and 1/4-inch outputs simultaneously, plus a separate 1/4-inch output for the square wave, all at a 100 ohm output impedance. Covering all three common connector types means the oscillator plugs directly into a pro console's XLR input, a consumer device's RCA jack, or an instrument-level 1/4-inch input without hunting for adapters. Output levels reach +11 dB on the sine and +14 dB on the square, enough to drive a real input to a useful reference level. The low 100 ohm output impedance lets it feed those points over a cable run without level loss. For a tech moving between pro and consumer gear on the same job, having every output ready at once saves time at each test point.

Switchable 30 dB Pad and VCO Control Input

A switchable 30 dB pad drops the output by a fixed, known amount so you can reference low-level inputs like a mic preamp or a sensitive test point without overloading them. Referencing at -30 dB is exactly what you need when calibrating gain stages that expect a whisper-level signal rather than a line-level tone. The MO2020se also accepts a 1.2 to 5 VDC VCO control input, letting an external voltage sweep the oscillator's frequency automatically. Voltage-controlled sweeping turns a static tone into a moving test signal for plotting frequency response or hunting resonances. Together these two features take the MO2020se beyond a simple tone box into a flexible instrument for real measurement work.

Compact, Field-Ready Build

The MO2020se runs on a 12 to 15 VDC external supply in a compact half-rack chassis built to travel between the bench and the job site. Keeping the unit small and externally powered means it drops into a service kit or sits on a crowded rack shelf without taking over the space. The rugged metal enclosure stands up to being carried into the field for install verification. Because it is purpose-built as a test source rather than a general-purpose lab generator, its controls are laid out for quick, repeatable setup. For an installer who needs a reliable tone at every stop, the portable build is what keeps the MO2020se in the kit.

Testing, Calibration, and Field Verification

The MO2020se's core work is testing and calibrating audio systems and signal chains, from setting levels and checking speakers, amps, and mixers to troubleshooting an installed system in the field. Injecting a known tone lets a technician trace a signal path stage by stage and find exactly where level is lost or noise enters. On the bench it verifies audio electronics under repair against a clean reference. During an install it confirms that every zone and output carries the signal it should before the system goes live. For service techs and integrators who need objective answers rather than a guess, the MO2020se is the tone source that makes a system measurable.