Analog Compressor/Limiters

Relevant Specifications



Microsecond
 (1ms), one millionth of a second.

Nanosecond
One billionth of a second - The Spectra Sonics 610 has the minimum attack time of 100 nanoseconds and a release time of less than 90 nanoseconds.

Signal to Noise Ratio
 
“A” Weighted
Wide bandpass filter with a maximum at 2.5 kHz with -20 dB attenuation at 100 Hz and -10 dB attenuation @ 20 kHz.                                      

This specification is notorious for masking low frequency “hum” and concealing high frequency and ultrasonic noise, Low frequency attenuation used under “A” weighting reduces 2nd and 3rd line harmonics by about 20 dB and 12 dB, respectively. In application, an “A” weighted specification can improve the noise measurement between 6-10 dB over an “unweighted” noise measurement.                                       

“Unweighted”
Wide bandpass filter, 20 Hz to 20 kHz with 18 dB/octave attenuation @ 20 Hz and 20 kHz, respectively. Used to specify a signal to noise measurement where all audio frequencies within the bandpass are equal. The Spectra Sonics Model 610 is specified with a signal to noise ratio of less than 80 dB below + 4 dBu output with -40 dBu input, (threshold, 600 ohm termination, 20 Hz to 20 kHz, unweighted).


THD
Total Harmonic Distortion: A form of measurement that identifies unwanted harmonically related signal to the original sine wave. In short, for a THD measurement to have any relevance requires a bandwidth relative to the operation of the device in application.                                     

Harmonic distortion (THD), for the Spectra Sonics Model 610 is below. 10%, typically less than .05%, 30 Hz to 20 kHz, @ +16 dBu, up to 30 dB of compression, release time such that attack and release does not occur successive peaks of the lowest frequency utilized.