how does current work in an amplifier?

Another question that comes to mind when selecting an amp is Total Harmonic Distortion.

I read on another Audiogon thread about what amp for Magnepan 1.7's. One suggestion was an Emotiva Audio XPA-2.

The EPA-2 is advertised at 300wpc @ 8 ohms and 500 wpc @4 ohms - at less than $1000!?!

However the THD is listed as less than 1% compared to Mac's, for example, which are listed at less than .004% THD.

So what's up with THD? When can you hear it? How do you hear it?

Ear is most sensitive to THD at higher frequencies. I'll let the guys that know fill in the blanks. Your ear is most insensitive at very low frequencies......which is why subs can get away with 5% distortion or whatever.....which, if it happened at 1000hz, would drive you from the room.

Don't worry about specs. Their is a relationship to feedback which some persons object to. Just for example, the Japanese amps of the 70s had amazingly low #s, but were high feedback designs. Again, the knowledgable ones will be along in a minute.

As for Emotiva? You could build the identical design of amp....#1 used all premium components, matched semiconductors, huge heatsinking on outputs, heavy gauge chassis, transformers it takes a forklift to move, and other 'quality' touches. MTBF is very high. Before being mass produced the piece was 'voiced' and sounded GOOD.

#2? Built with parts from Fry's or some catalogue. Just the values called out, with no matching, or thought of other characteristics of the part.....Caps have a resistive and an inductive component, for example. Everything else was built or sourced with price in mind. Meets specs? Sure. Sounds good, too....but not quite up to #1s level. More production variance and less lifetime. Sales price point?.....A heck of a lot lower than #1.

Just my opin.

Unsound, most of the studies I am aware of in this area are so new that they are not published yet. However, one of the people conducting them is a Nobel Prize neuro-chemical scientist. I understand that High Emotion Audio has based a lot of their work on his studies.

Dsper - the owner at the store I deal with is constantly telling me to ignor specs and just listen. He's given me some extrememe examples of equipment that he's heard where the actual sound was the opposite of what was expected. It was something crazy like 9 wpc and a THD in double digits that he said was amazing.

He also noted that there isn't really any true regulations going on to verify specs. Many of the specs are taken at the one and only ideal frequency. Think Ford commercials.

Specs are advisory to the knowledgable and misleading to those who aren't.