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M-Box USB Audio Interface

Input Distortion and Noise (M-Box Gain at 1 o'clock)

Output 1 kHz Distortion and Noise (M-Box Mix Ratio at 2 o'clock; digital waveform level -13dBFS):

Full duplex 1 kHz Distortion and Noise(M-Box Input and Mix Ratio both at 1 o'clock; digital waveform level -13dBFS):

Measurement conditions:

• Measurement software: Mac the Scope 4X 4.1, 2048 point (X2) FFT, Square window function, linear frequency axis.
• Stimulus signal was generated by Mac the Scope / Waavebox. Signal: 1 kHz, DIGITAL LOCK enabled, 2048 sample latency (e.g., sequence length).
• Measurements were made at 44.1 kHz sample rate (except where noted), 24/32 bit. Channel 1 is shown, and also represents Channel 2.
• Connections were made by connecting input and output with 1/4" TRS or TRS - XLR cable.
• Input and output gain of M-Box set to minimum, except full duplex, where signal levels were manually adjusted to obtain optimum performance.
• Plot range is -160 dB to 0 dBFS.
• Reference Measurement device for input and output tests: LynxTWO
• Note: the M-Box has uncalibrated input and output gain pots. After careful level matching using the Reference Measurement Device, optimum results were obtained. Best level match to -10 dBV standard was with input and output (mix) pots set to approximately 1 o'clock.

Note: the distortion measurements may be replicated with the free, demo version of Mac the Scope (the session timeout limit provides ample time for making the measurement).

• Here are links to some other measurements.
• Here is a procedure for making the distortion measurement.

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