A dual audio level meter instrument comprising:
- an input clock/data recovery circuit receiving an input serial digital audio signal and providing as output a clock signal at a predetermined sampling rate, selected from a group including 32 kHz, 44.1 kHz and 48 kHz, and a reconstituted serial audio data signal;
- a serial-to-parallel converter receiving as input the clock signal and the serial audio data signal and providing as output L and R signals representing the left and right audio signals respectively;
- a sum processing circuit, receiving as input the L signal and the R signal, constructed and arranged to provide as output an L+R signal representing an instantaneous sum of the R and L signals;
- a difference processing circuit, receiving as input the L signal and the R signal, constructed and arranged to provide as output an /L-R/ signal representing an instantaneous difference between the L and R signals;
- selector means constructed and arranged to receive as input the L signal, the R signal, the L+R signal and the /L-R/ signals and to select as output, and thus cause to be displayed, a pair of subject signals as selected by the user from the following two pairs:
- (a) the L signal and the R signal and (b) the L+R signal and the .backslash.L-R.backslash. signal;
- rectification process means, receiving as input the pair of subject signals, constructed and arranged to act upon data thereof in a manner to apply full-wave rectification thereto and to thus provide a pair of rectified signals representing audio data of the subject signals in rectified form;
- an average detection process circuit receiving as input the pair of rectified signals, constructed and arranged to provide a pair of average signals each representing a quasi-average amplitude of the corresponding rectified signal;
- a peak detection process circuit, receiving as input the pair of rectified signals, constructed and arranged to act thereupon in a manner to provide a corresponding pair of peak signals representing peak amplitude levels of the corresponding rectified signals;
- linear-to-logarithmic conversion means, receiving as inputs data of the pair of average signals and the pair of peak signals, constructed and arranged to convert input data from linear to logarithmic form and to provide as output a pair of logarithmic average signals and a pair of logarithmic peak signals;
- an average ballistics process circuit, receiving as input the pair of logarithmic average signals, constructed and arranged to impose a predetermined rise and fall times upon the logarithmic average signals and to thus provide a corresponding pair of ballistically-conditioned logarithmic average display drive signals;
- a peak ballistics process circuit, receiving as input the pair of logarithmic peak signals, constructed and arranged to impose predetermined rise and fall times upon the logarithmic peak signals and to thus provide a corresponding pair of ballistically-conditioned logarithmic peak display drive signals;
- a dual electronic display device, receiving as input the pair of ballistically-conditioned logarithmic average signals and the pair of ballistically-conditioned logarithmic peak display drive signals, comprising a dual array of LED segments constructed and arranged to each display average values in bar graph form and to display peak values in dot graph form on each corresponding array as independent representations of corresponding audio data of the respective subject signals;
- over-range warning detection means constructed and arranged to monitor audio data of each of the subject signals, to detect therefrom occurrences of predetermined proximity of audio level data to a maximum audio level limit and to consequently generate an over-range warning signal, said display device, receiving as an input the over-range warning signal, being constructed and arranged to respond thereto by introducing a visually recognizable color change in three LED segments disposed at a top scale region of the corresponding array of said display device.