This module has now been updated to the NXF50 R1 True Class A Amplifier Module. More details to follow soon. The NXA50L now has the entire input driver stage power supplies on board, so all that is needed is a small power transformer to run it. The remaining power supply for the output stage is provided by an external power board like the PSU One or the PSU Two board.Typically this would be one of the PSU Two boards or a suitable hand wired power supply.The Class A module also has a much more complex and accurate bias control circuitry. The New NXA50L amplifier module is now available for order.The new Class A module has electronic voltage regulation for the Input-VAS stages, DC Servo for less than 1mv DC offset, Baker clamps for perfect high frequency clipping behavior and 4 position DIP switch selection for 9dB of gain adjustment starting at around 27dB down to 18dB of Global Gain.The PCB has been designed around the NXV500L form factor and the 4 main output devices have the same positions as the NXV500L module, so for those that already have the 500L or R2 module and want to try out the Class A module, the new Class A module is a practical drop in replacement, with exception to a power supply replacement or reconfigure to suit the Class A module requirements.With 4 dual die lateral MOSFETs on board this module can deliver 50 watts in Pure Class A into 8 load.. After which the 4 ohm load power output operates in Class AB to 90 watts.The Input-VAS stage supply requires +-42 volts DC input from a raw DC supply to feed the on board power voltage regulators which the regulate this down to a very smooth and quiet +-38 VDC.The Output stage just requires +-35VDC from a 300VA raw DC supply.DC supply filtering for the output stage is recommended at 40,000uf per voltage rail as a starting point. But I would use at least double this amount for best performance. The Class A module has been designed as a Mono Block amplifier in mind, so two separate power supplies as described above would be highly recommended for the best performance.Total Harmonic Distortion for 1 watt is 0.003% 1khz and 10khz at 0.005% into 8 ohms loads15 watts it is almost the same at 0.0035% 1khz and 0.0047% 10khz.Signal to Noise Ratio is -103dB at 27dB Gain.The PCB dimensions are 220mm x 65mm HPA-NXA50L Specifications 50 Watts RMS sine wave into 8 Ohms 100 Watts RMS sine wave into 4 Ohms Biased into Pure Class A Power Bandwidth 3.5hz to 350khz -3dB THD+N 0.003% 1khz, 10khz 0.005% @ 1 watt - 8 ohms THD+N 0.0035% 1khz, 10khz 0.0047% @ 15 watts - 8 ohms THD+N 0.0055% 1khz, 10khz 0.008% @ 45 watts - 8 ohms Dampening Factor At 100hz 8 Ohms = 800 RCA Single ended Input impedance 22k Ohms Single Ended Input Gain = 27.0dB Position One. Single Ended Input Gain = 24.0dB Position Two. Single Ended Input Gain = 21.0dB Position Three Single Ended Input Gain = 18.0dB Position Four Signal to Noise Ratio -115dB @ 18dB Gain Recommended Linear Voltage Supply for Output stage +-35 Volts DC Recommended Linear Voltage Supply for Input stage 42 Volts DC 42 volt raw supply is regulated down to +-38 volts DC One x 300VA power transformer with 2 x 25VAC secondary winding. One x 50VA-80VA power transformer with 2 x 30VAC - 35VAC secondary winding. Printed Circuit Board Dimensions 220mm x 65mm Minimum Heat Sink Conrad MF35-151.5 per channel. Recommended parts to build a Mono Block NXA50L Amplifier. 1 x HPA-NXA50L Mono Amplifier Module 1 x HPA-Power One R4 AC Mains Controller 1 x 300VA power transformer with 2 x 25VAC secondary winding. 1 x 50VA - 80VA power transformer with 2 x 30-35VAC secondary winding. 1 x PSU One or PSU Two power supply board for the output stage supply 1 x Conrad MF35-151 heat sink 350mm x 100mm x 48mms Recommended parts to build a Stereo NXA50L Amplifier. 2 x HPA-NXA50L Mono Amplifier Module 1 x HPA-Power One R4 AC Mains Controller 1 x 625VA power transformer with 2 x 25VAC secondary winding. 1 x 50VA - 80VA power transformer with 2 x 30-35VAC secondary winding. 1 x PSU Two R3 power supply board for the output stage supply 1 x Conrad MF35-100 heat sink 350mm x 100mm x 48mm
