Hi David,

A switching amplifier with modulated supply should also be able to do the trick.
At 15 watts, a single transistor class E amplifier comes to my mind.
For example, the modulation can be made by an op-amp and a darlington 
transistor.
If efficiency is an issue, PWM modulation is more elegant but away goes the
simplicity...

Clint Turner KA7OEI has some nice information on a PIC based PSK-31
beacon TX that uses a class E PA with a linear modulator:

http://www.ussc.com/~turner/


73
Johan SM6LKM

It's been a few years since I looked at Audio Amp IC's on the LF bands, but I'm now trying to find one that works to some degree at 136kHz.

I need to find an audio IC capable of about 15 Watts as a minimum.

It's for use with a standalone PIC based PSK transmitter that uses the G3PLX Varicode, I just thought that a good IC would minimise the component count.

Regards
David   G0MRF