AXT Systems

PA-4 Mono 600W Class-D Amplifier
PA-4 Top Side
PA-4 Side View
The PA-4 class-D power amplifier is a mono version of the PA-3 stereo amplifier. Using bridged and parallel connections it increases the current capacity by 2 and hence the power by 4.

It is also based on the TPA3255 class-D amplifier chip, which is capable of 2-channel output of 150W into 8 ohms with the appropriate power supply.

The module requires a +/-12V power supply for the input circuitry along with a power rail for the power amplifier section (+38-48V). I use a PSU-12 module for the +/-12V section and a ConnexElectronic SMPS for the power amplifier rail. This combination provides for a very efficient amplifier system.
For heatsinking (when running it at reasonable power levels) I have attached a copper bar to the top of TPA3255 chip with thermal paste and attach a plate as shown in the photograph with standoffs. The plate is them mounted to the heatsink. 

The amplifier is fully balanced (line level input) and uses a small MCU (PIC12LF1552) for generating the LED indications from the signals provided by the TPA3255 status pins. LED indications include overload and overtemperature warnings and shutdown status.