Starting a Shop, Need some advice.

[mikechec9]

end result is THD ratings on amps are pointless by themselves, and not something to pick or pan an amplifier based upon solely when making a decision.
amplifier distortion, when the amp is used within it's limits, is inaudible.

But Glass, doesn't the thd imply-to a degree-the limits of an amp. That is, how much an amp has to strain in order to produce said power. An amp with a significantly lower thd at an identical rms suggests greater capability to produce that power. Regardless of how audible the distortion is or isn't. Correct or no?

[mikechec9]

So in basics I won't be doing my customers wrong if I offer them Interfire amplifiers as an money saving option and recommend they spend the extra they save on higher quality speakers when on a limited budget

A lesser quality amp does not suggest that it necessarily produces more distortion. There are plenty of amps that have identical power limits, but lesser build quality. These amps thus cost less money. Is there a bit of audible difference? No. But an amp like the Interfire (at least the 600 model) isn't one that I would suggest to my customers. Less money or not. It's not a decent sounding amp. The more it attemps to produce its rated power, the more it clips. The more it clips, the more distortion it produces and the worse the reproduction.

[smoker]

smoker, wasn't disputing you, just expounding on my previous statement so others would have a better idea of what we were talking about.
end result is THD ratings on amps are pointless by themselves, and not something to pick or pan an amplifier based upon solely when making a decision.
amplifier distortion, when the amp is used within it's limits, is inaudible.

i didnt get that feeling....i was just clarifying...

[GlassWolf]

nah. the power supply defines the dynamic headroom of an amp. A good amp has a PS capable of at least 3X the amp's rated output.
The THD more defines the tolerances and design of the amp itself, and how transparently the amp can produce the amplification.

[Jonathan]

I think there is a simple test in line for if amplifier distortion is a problem.

Ask said Audiophile to set the gain by ear, at the point where he hears audible distortion, be it a 0db reference tone, music, whatever he likes. Preferably on a test bench with a stable power supply to ensure accuracy (this would be for the benefit of the audiophile)

Once gain is set, connect the amplifier to an oscilloscope, at the same level, and observe the sine wave. I'll bet dollars to donuts the transistors are saturating, and that the distortion is much higher than it is thought to be.