Overview The NTI A2 is a comprehensive, high performance two -channel audio test set. It includes a flexible generator, based on a Digital Signal Processor (DSP) and a high performance analyzer providing a wide variety of measurement functions, as there are • Level absolute (two -channel) in μV, mV, V, dBV and dBu or dBm • Level relative in *1, % and dBr • Level selective in μV, mV, V, dBV and dBu / dBm • Total harmonic distortion & noise (THD+N) in % and dB • IMD (Intermodulation distortion) in % and dB • Wow & Flutter in % • Noise (absolute), weighted and unweighted, in μVq, mVq, Vq and d Bq • Noise (relative), weighted and unweighted, in *1, % and dBr • Crosstalk (frequency selective) in *1, % and dBr • Frequency (two channels simultaneously) • Phase (interchannel) in the range of ±180°. In the METER display mode, all measurement results are displayed in numerical form as large digits and in analog form through a bar-graph. Additional parameters like the I/O- frequencies and impedances, the input levels and the generator settings are permantly shown. The standard sweep capabilities of the A2/A2-D allow to perform • Frequency sweeps • Amplitude Sweeps • Time Sweeps • Table sweeps with freely definable pairs of frequency and level (with Option AO1) Sweeps can be controlled by the built-in generator or by an external source (e.g. test tapes, test CDs or other NTI A-series instruments) at a remote location. Several traces can be recorded and displayed in the GRAPH mode, while up to four complete graphs may be stored in the internal non -volatile memory of the A2/A2-D. This allows for instance to record swept measurements in a studio and to print out the results in the office later. Another powerful diagnostic aid of the A2 is the SCOPE function. In this mode, the waveform of both input channels is shown on the LC-display just like on a dual trace oscilloscope. If set to the THD+N function, the A2/A2-D shows both the original signal and the distortion residual. In other measurement functions, the main input signal is shown as a single trace. All measurements of level - except noise - are true RMS rectified. Noise is measured as quasi-peak value according to the CCIR 468-3 standard. Both a 400Hz high -pass and a 22Hz-22kHz band-pass filter are available as a standard. The two inputs of the A2/A2-D are DC -isolated up to ±300Vp, and equipped with selectable input impedances to optimally match the output impedance of the device under test (DUT). As an option, both inputs may also be Phantom-powered. The normalized input signals are available at the BNC connectors at the rear panel of the instrument. A small, built-in loudspeaker allows acoustical monitoring of the measured signal. The versatile generator of the A2/A2-D, based on a Digital Signal Processor, is capable of generating a large number of different test signals over the full level & frequency range. • Low distortion pure sine signal • Low distortion warbled sine • Dual -tone IMD signal, covering all standards • Symmetric square wave (50:50 duty cycle) • Asymmetric square wave (40:60 duty cycle for phase reverse check) • White noise • Pink noise The output impedance (<15Ω up to 600Ω) can be adjusted in a wide range as well in order to match the input impedance of the device to be tested. As an option, a RS-232 serial or IEEE-488 parallel interface may be installed into the instrument to remote control all A2/A2-D features from a PC. Regardless of the type of interface, AS04, a comprehensive Windows based software package is included, supporting all operation modes, offering the possibility to store all results, and allowing to write program sequences in the easy-to-learn Audio Measurement Sequence Language (AMSL) for fully automatic measurements.