ROSTEC LMA8, Руководство пользователя

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LMA8 Mic/Line Preamplifier
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Unwanted HF feedback and oscillation in studio installations
It may seem risky to install a piece of equipment witch exhibits such fast speed and high gain at the same time in a studio
environment. Normally, when the input signal path and output signal path of a amplifier with high gain and high frequency
response passes too close to each other, high frequency oscillation may occur.
This usually happens if the signals are routed through a mixing console of inferior quality, a bad patch-bay or through a
piece of equipment with bad crosstalk performance.
But not to worry; LMA8 has a mechanism in place to prevent such unwanted HF feedback.
HF oscillation in complex studio installations is prone to occur when both gain and frequency response is high. The LMA8
uses a well established technique that employs a "constant gain/bandwidth product" function. In short; it works by
reducing the upper frequency response when the gain is increased. The numbers below illustrates this:
Gain: +10 dB
Upper frequency response (-0.1 dB) 200 kHz
Gain: +20 dB Upper frequency response (-0.1 dB) 153 kHz
Gain: +30 dB Upper frequency response (-0.1 dB) 130 kHz
Gain: +40 dB Upper frequency response (-0.1 dB) 90 kHz
Gain: +50 dB Upper frequency response (-0.1 dB) 47 kHz
Gain: +60 dB Upper frequency response (-0.1 dB) 24 kHz
The change of the frequency response is not audible and it does not affect the internal gain structure, noise figure or
distortion figure.