Axiom Home Page Forums General Discussion Technical Questions Amplifier - General Information Request

In reply to:

---

If you make it to Southern California, Bren, I'll be glad to give you a demonstration. Each component, including speakers, can influence the width, depth and height of the soundstage.

---

I'll take a pass on the travel... it's no fun to travel to do for free what one can stay at home and do as work.

All I meant was you hear these same buzzphrases all the time (this cable/cord/woodchuck will --------) It makes me wonder what percentage of the population uses the same metaphor for the same phenomenon.

Bren R.

Looks like you guys had some serious fun while I was asleep last night. I have still seen nothing beyond my initial conclusion that convinces me I need to be saving my spare change to go out and get a big honkin' amp.

Ive been trying to follow all this discussion across several threads. It seems that most people have the opinion that amplifiers shouldnt/dont make a difference.

I'd like to ask a question (Im talking about amplifiers here, not receivers that are made to change the sound with surround effects, etc)...

Considering that amplifier are rated by their manufacturers at % of total harmonic distortion. Isnt it logical to assume that they have tested to make sure that is the case?

A 0.07% THD would seem to mean that over the entire frequency range that the amplifier wouldnt change any input sent to it more than that amount. Are these ratings wrong/misleading?

If the ratings are correct, then is it possible for the human ear to hear that low of a distortion?

Jon, specific published figures result from what the engineers tested in the lab, and certainly aren't "lies", as some rather naive comments claim. Whether they're misleading is another matter; first, the test conditions(e.g. frequency range)may vary, and in addition there may be an implication that the very low distortion figure is of audible significance. The audibility of THD varies with the type of program material, but something on the order of 0.07% is well below audibility even on pure sine wave test tones. It's frequently said that distortion on music would have to be greater than 1% to be audible(e.g. one of the FTC regs uses a 1% distortion standard)and on complex full orchestral material the threshhold in David Clark's ABX tests was about 3%.

So, there's a bottom line which principles of scientific engineering teach us(supported by blind testing results)and which certainly isn't something as trivial as personal opinion based on casual listening. Amplifiers having flat frequency response from 20-20,000Hz with inaudibly low noise and distortion(common these days)don't create audible differences in sound, regardless of the nameplate or pricetag.

Our senses lie. Why should I trust my ears more than I trust my eyes? The human sensory array/brain processing unit is not, by far, the most accurate thing in the world.

And that's all I'm saying for now.

I can't believe I'm going to join in this fray....

The bottom line is those lines look sloped. All the science in the world isn't going to make them look straight. The same can be said for audio illusions. Just because something can be scientifically measured to tell you it should sound a particular way, doesn't mean it's going to sound that way to you.

I'm not trying to join either camp on this issue, but your optical illusion example doesn't really help your case.

OK...that's the last I'm posting on this. I feel dirty now...I've got to shower.

Yes, but all the science in the world can measure them as straight. My point was that our senses cannot be trusted to give us accurate information, not that amplifiers are like sloped lines.

And my point was what is accurate? If it graphs as accurate, but sounds like crap? Or is accurate something that sounds great, but graphs like crap?

Personally I'll take what sounds good over what graphs good any day.

Damnit...now I've got to shower again.

Good point. Perhaps this was not the correct discussion to inject that thought into.

What is being measured? A single frequency test signal? A sine wave?