How to build a high-frequency (>20kHz) driver for LEDs? I'd like to build a LED lighting for my house. I've made preliminary tests and I've realized that my 12V transformer emits a considerable electric hum at the Arduino's PWM frequency range (PWM signal from Arduino gets amplified by external amplifier powered by the transformer). 

I know, that I can reduce the audible noise if I will drive the PWM at higher frequency, beyond the human ear's audible range.

AFAIK Arduino itself is not able to give me 8-bit PWM at the >20kHz range. Do you know any feasible hardware high frequency PWMs that will work with the Arduino?
Just change the timer prescaler to a lower value. 

E.g. timer2 (PWM pins 3 and 11) has the prescaler set to clock/64 and runs at around 500Hz. So changing it to clock/8 will result in 4kHz. (Sorry, no clock/16 available).

TCCR2 &amp;= ~_BV(CS22);//clear CS22 bit
TCCR2 |= _BV(CS21);//set CS21 bit