SPL Crescendo duo

Crescendo duo is a two-channel mic preamp whose audio circuitry runs from internal rails of +/-60 V, using the maker's own SUPRA operational amplifiers. The higher rail voltage gives an input ceiling of +32.5 dBu, which the maker states is 12 dB more headroom than typical +/-15 V designs. This is the v2 revision, which changes the front panel, the housing and the gain steps compared with v1.

Both channels have the same controls: 48 V phantom power, polarity reversal, a 6 dB/octave high-pass filter at 120 Hz, a 20 dB PAD, and a VU-10 switch that lowers the meter reading by 10 dB so high levels stay visible. A stepped Mic Gain switch covers +18 dB to +70 dB, and a switchable output control adds +/-10 dB for matching following AD converters, for a total of 80 dB of gain. Each channel has two parallel outputs, so one signal can feed two devices without an external splitter.

Inputs and outputs are balanced XLR. Power comes from an internal linear supply with a shielded toroidal transformer, switchable between 115 V and 230 V. The front panel is 4 mm black anodized aluminium with milled aluminium knobs, and the housing is powder-coated steel. The unit is made in Niederkrüchten, Germany.