Audio Precision has two primary analyser product lines; the APx and the 2700 series. The former has been focussed on ease-of-use, on programmability, and has had what has been regarded as a simpler user interface. It (the Apx) has tended to be used more often in a production environment, or for general 'troubleshooting' duties. The 2700 series has been the company’s highest-performance unit: as Audio Precision notes, one of the critical parameters of such an instrument is how much (or how little) distortion is introduced by the measurement process itself. The 2700 has been the company’s ‘flagship’ for lowest total harmonic distortion plus noise (THD+N) figure.
Now, with the APx555, the company has combined those attributes in one unit; it has increased THD+N performance and added different user operating modes to simplify making exacting audio measurements in both manually-driven, lab-environment; and in programmed, operating environments.
The Apx555, AP says, has improved measurement accuracy, speed, flexibility, automation and ease-of-use for developers of audio components, equipment and systems. With a typical residual THD+N of -120 dB (conservatively specified on its data sheet at -117 dB), the two analogue channels of the APx555 claim to add the lowest noise and distortion of any audio analyser yet built. This performance is coupled with 1 MHz bandwidth (mono) and an industry-leading FFT resolution of 1.2 million points. AP notes that 24-bit resolution is maintained to 1 MHz. The generator is capable of producing low distortion sine wave signals up to 204 kHz, at high-level amplitudes up to 26 Vrms. This increases the user’s confidence that the results they see owe nothing to the test system itself.
This plot shows harmonic generation (spurs) from earlier-generation instruments, with that of the APx555.
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