I finished the project of the most simplest and cheaper modular instrument amplifier. The final amplifier have output power between 70W and 300W for 4 and 8 ohm speakers. Three several modules required for this project if bridged and paralleled modes required. The 4th module is the speaker protection. The amplifier can be built as:
Single amplifier with only one module with 1 TDA7293 or TDA7294 / channel
Bridged amplifier with 2 modules / channel
Paralleled amplifier with 2 modules / channel
Combined bridged and paralleled with 4 modules / channel
Paralleled simple or bridged amplifier, but with 2 paralleled module
The modules can be connected with 15 pin connectors instead of wires. The single, bridged, and paralleled amplifier modules are not same, one for the first and the most important “main” module, one for bridge connection, and one for parallel connection what can be used for both main and bridged modules. The last 4th module is the speaker protection, must be placed to the middle of stereo configuration between left and right channels.
The official datasheet contains all modes of TDA729x circuits. The TDA7294 is very cheap, but cannot use for paralleled mode, and no clipping led output. The recommended max. power supply voltage is +-40V. The TDA7293 have paralleled mode (where only the power stage works, the preamp stages off), the max. power supply voltage is +-47V, and clipping led output available. The maximum output power of one circuit is 70-75W of TDA7294, and about 80-100W of TDA7293.