Total Harmonic Distortion...?

Question

At what point should you stop reading into THD numbers? I am talking about a home theater receiver. All are mid range models that I am looking at. I have seen the number range all the way from a 0.03%-1.0%. At what point are these numbers inaudible? What does the number have to reach to stay away from a receiver?

Answer 1

It somewhat depends on how sensitive you are. Personally I'd look for a receiver with less than 0.1 % THD at the rated output. Since THD rises rapidly much past the rated output for most receivers all you are really doing is defining what the limits of power are, using THD as the indicator.

The link below (a basic guide to A/V receiver selection) says:

"If you want a good home theater experience and your budget is flexible enough, we strongly recommend choosing a receiver with a power specification that reads something like "80 Watts RMS into 8 ohms per channel,

20 Hz to 20 kHz, all channels driven simultaneously, with no more than 0.08% THD".

It isn't too difficult to get receivers with that kind of spec, so while you may be tollerant of something more why take the chance?

Answer 2

It depends.The ear is more sensitive to odd order harmonics than even.Solid State Amplifiers emphasise odd order harmonics. Tube Amplifiers emphasise even order harmonics. Therefore solid state amps of 0.1 % or less will be ok. Tube Amps. of up to 1.% are  quite acceptable.This is one reason why Tube Amplifiers have a sweeter more unfatiguing sound.

Answer 3

THD is an extremely misleading number. There are some seriously high dollar items out there with very high THD values up into the 5% range. Some of these amps sell in the tens of thousands of dollars.  You will most likely clip your amp before you can even hear THD.

In most cases I usually try to stick to .1% or less. Mostly as a rule for myself.

For most intensive purposes if you stick with good quality components like Sunfire, B&K, Anthem, Denon, Yamaha, Onkyo, Pioneer and steer away from the HTIB systems from walmart it will be a mostly useless number. It is a marketing  tool more than anything.