The A1 microphone pre-amplifier stage uses a transformer-balanced, discrete, class A design with a current-feedback amplifier architecture for low distortion and wide bandwidth across the full gain range. The pre-amplifier sports very low noise for a wide range of source impedances, across the full gain range. The gain is variable in 3 dB steps between 15 and 60 dB. A 24 dB pads allows to feed line levels as well. A high pass filter can be switched in. The corner frequency can be selected to be 40 or 80 Hz.
The de-esser section uses an advanced mixed signal design: The direct signal path is fully analog while the side-chain works in the digital domain. This enables the use of a low distortion precision MDAC (Multiplying D/A Converter) as the variable gain element. The side-chain is built for very low latency, using a 500 kHz sampling frequency.
Front panel controls
The front panel controls for the de-esser section are knobs for frequency, bandwidth and threshold. Further parameters (ratio, attack and release time) can be set via DIP switches.
The output also uses a transformer balanced design with a high maximum output level of +27 dBu. An additional output gain potentiometer allows to set the output level in a wide range.
The A1 is used as a microphone pre-amplifier for recording or for live purposes with the option to do de-essing on the fly. As a bus de-esser it is used during mix down or mastering in a stereo fashion, i.e. by linking the side-chains of two modules.