General Overview

The Neve 33415 module uses a BA438 class-A discrete input module.  The original amplifier used the BA440 class-AB output amplifier, but this one has been self-modified to use the Phoenix Audio International TF1 class-A output amplifier and transformer giving a more open, detailed, sound.  The input for this amplifier is provided as both 1/4" TRS and XLR.  The phantom power and phase polarity are both switchable.  The first two-position rotary switch controls the input impedance of the 33415 at either 1200ohms or 10k ohms, also providing 30dB of attenuation.  The gain is distributed evenly between the two stages to provide the sound as intended when the amplifier was initally designed.  The gain is selectable via a 9 position rotary switch in 5dB increments.  The output level is a linear taper fader with a resistor shunt across the wiper/input to provide a near-log function.  Output is available in both balanced and unbalanced configurations. 

The Power Supply for this unit is rackmounted separately and provides the transformers, full wave rectifiers, and pre-regulation to the unit via a 4 Pin XLR connector.  The on-board regulator takes the +32V from the pre-regulator and regulates it down to +24V to supply the two amplifiers.  Additionally, +48V phantom power is derived from the separate +52V pre-regulated input.  The phantom power is fully regulated using a separate power transformer, it is not achieved using a voltage doubler or tripler circuit.  The dual regulation methodology used allows for remote mounting of the power supply and provides extra filtering.  All of the regulators are adjustable avoiding the noisier fixed regulator chips.