Best Of

muncybob wrote: »

"Question is, will 60wpc into 8ohm or 120w into 4ohm be enough power? '

That is indeed the question of the day. Time will tell once she orders the amp probably using Amazon for ease of return. First we'll wait for the speaker cables to arrive & see if that makes much of a difference with the AVR....I'm not optimistic about this but she needs better wires anyhow.

What does PFFB do? What would be the audible difference betwenn one unit having it and the other not?

Post-Filter FeedBack. Broadly similar to the feedback loop used in Class AB amplifiers (and/or also the specific feedback employed in PP Ultralinear vacuum tube amplifiers) to broaden frequency response, reduce distortion, and lower amplifier output impedance. The goals are essentially the same... but mostly (I think) to remove the load-dependency that is a hallmark of PWM (Class D) amplification.
Amusingly, I think that the load-dependent changes in frequency response might be (have been) one of the primary reasons that some "early"* Class D amplifiers (e.g., those using the Tripath "Class T" chipset) found a fanbase some years back with their "tube-like" sound.

_____________
* Not that early! Commercially-available Class D amplifiers date back to the 1960s and the famous/infamous Sir Clive Sinclair... the Class T amps were a late-90s/early 21st Century thing.

EDIT: The "filter" in PFFB, in case it isn't obvious, is the low-pass filter that's required on the output side of all class D amplifiers to remove the ultrasonic crud from the amplified output signal fed to loudspeakers. It needs to be removed for the same reasons as the HF 'hash' that is filtered out in a DAC. In and of itself, the ultrasonic noise is inaudible by definition, but it can wreak havoc with tweeters and/or result in audible artifacts by 'heterodyning' with other signal components, producing artifacts ("beat products") in the audible range.