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BAE 1073 DMP | Media

Microphone Preamplifier
Published March 2012
By Hugh Robjohns

These images accompany BAE 1073 DMP in SOS March 2012 (/sos/mar12/articles/bae-dmp-mkii.htm).

The green trace shows the residual noise floor (at minimum gain) of the first production batch of DMPs, with mains-related harmonics peaking some 35dB higher. The purple traces show the background mains hum being picked up by the AP test set through its audio cabling.The green trace shows the residual noise floor (at minimum gain) of the first production batch of DMPs, with mains-related harmonics peaking some 35dB higher. The purple traces show the background mains hum being picked up by the AP test set through its audio cabling.This plot shows the considerable reduction in the amplitude of mains harmonics after the GOSS band modification added to later production units, and available as a retrofit for the earlier units.This plot shows the considerable reduction in the amplitude of mains harmonics after the GOSS band modification added to later production units, and available as a retrofit for the earlier units.A set of frequency responses at different gain settings from the DI input. The response is extremely linear with a wide bandwidth at low and moderate gain settings, but reveals progressive LF roll-off and a tendency towards an extreme HF resonance at high gains.A set of frequency responses at different gain settings from the DI input. The response is extremely linear with a wide bandwidth at low and moderate gain settings, but reveals progressive LF roll-off and a tendency towards an extreme HF resonance at high gains.Very low levels of distortion at minimum gain, with predominantly second and third harmonics at roughly equal amplitudes.Very low levels of distortion at minimum gain, with predominantly second and third harmonics at roughly equal amplitudes.Slightly more second harmonic than third, with raised levels of higher-order distortion products are revealed at maximum gain.Slightly more second harmonic than third, with raised levels of higher-order distortion products are revealed at maximum gain.Overall frequency response of the microphone preamp at all gain settings. The response is very linear for gains below about 50dB, with subtle but progressive bass roll-off and HF brightness increasing at higher gains. At extreme gains the bandwidth starts to be curtailed quite dramatically above 30kHz.Overall frequency response of the microphone preamp at all gain settings. The response is very linear for gains below about 50dB, with subtle but progressive bass roll-off and HF brightness increasing at higher gains. At extreme gains the bandwidth starts to be curtailed quite dramatically above 30kHz.  

Published March 2012