Microphone Preamplifier with High-Pass and Low-Pass Filter
The V778 ist almost identical the the preamplifier V776, but it leaves out the additional line input and the DI input. If only a microphone preamplifier is neede, the V778 offer the best solution.
The microphone section and the high-pass and low-pass filters are totally identical to the V776.
The microphone input is alsways transformer balanced and floating; the output can be transformer balanced or electronically balanced. The entire audio chain employs symmetric circuitry, and the headroom level from input to output is +30dBu.
The balanced and floating input is equipped with oversized torodial transformers. The common mode rejection ratio of the microphone input is better than > 76dB @ 15kHz. A stepper switch with calibrated positions provides coarse gain adjustment. Below 22dB the switch changes the pad, so that in every setting an optimal gain is maintained. Another control with a range from 0dB to +10dB is used for the fine gain adjustment. The maximum gain of the unit is 80dB. A passive subsonic filter with the edge frequencies 20, 40 and 80 hertz can be activated directly in the input. The LC filter uses the primary winding of the input transformer and prevents the amplifier from subsonic disturbances and foot fall sound that can cause intermodulation effects. Two knobs adjust input impedance for the microphone load. Resistive load can be applied with the values 200 ohms, 300 ohms or 600 ohms. For the capacitive load, the values 0.33, 0.68 and 1.5nF can be selected.
The high-pass filter has a steepness of 24dB/octave and a range of <20Hz to 300Hz. The low-pass filter has a range of >20kHz to 2kHz and a steepness of 12dB/octave.
A peak meter indicates the output level. The Ø switch rotates the input phase.
The V778 microphone preamplifier is a standard V700 module and fits into standard mounting frames.