Total Harmonic Distortion

[ScottMc]

Hi Everyone!

After reading some threads on this forum I became curious about Rotel.
I went to the Rotel website (very nice), and I noticed that they always publish the Total Harmonic Distortion for their products.

I’ve also spent some time on the Yamaha and Onkyo websites. Onkyo also publishes the THD, but Yamaha doesn’t. At least I couldn’t find it anywhere.

Why doesn’t Yamaha publish the Total Harmonic Distortion for their products?

Many years ago I purchased a Yamaha receiver, and at that time I remember that they did publish the THD for their receivers.

Thanks,

Scott

[littlesaint]

Their USA site does not have THD numbers (that I could find anyway).

The Japan site does.

http://www.yamaha.co.jp/english/product/av/products/index.html

[Glen B]

Scott, THD and IM distortion figures in modern amplifiers is low enough to be of no significance to anyone but a "spec watcher". I'm sure you have not seen distortion numbers being debated as a basis for product selection in threads here at HT Guide. People have learned to rely on how an amp sounds in making their purchase decision. In the past 12 months alone, I have owned amplifiers from five different manufacturers (soon to be six - I collect and restore vintage amps) and if you asked me what the distortion figures of either of them were, I could not give you an answer. Its just not something I pay attention to.

[ScottMc]

Ok, I admit it... I'm a Spec Watcher.

I guess I don't need to be too concerned about THD, but I still like to look at the Specs (for fun).

Thanks for the replies,

-Scott

[M3-SRT8]

Their USA site does not have THD numbers (that I could find anyway).

The Japan site does.

http://www.yamaha.co.jp/english/prod...cts/index.html

The US Site does as well. Look in the last pages of the various pdf files for the product at Yamaha.com and you see them.

Incidently, Yamaha was one of the first (if not the first) to publish THD specs for their products way back in the 70's.

I checked two models (RX-V3800 and RX-Z11) and both had THD specs on the website.

LJB 8)

Yamaha makes great stuff BTW, I own the RX-V3800.

[Karma]

Ok, I admit it... I'm a Spec Watcher.

I guess I don't need to be too concerned about THD, but I still like to look at the Specs (for fun).

Thanks for the replies,

-Scott

HI,
As said above, modern amps have such low THD that it is of little practical use. However, if the distortion is high the amp will sound bad. To a repair tech, THD is very important.

Of more importance is to understand what the spec means and how is is measured. Doing this will add to your understanding of audio. A few years ago low THD was the primary problem faced by the engineers. We must give them a lot of credit to have suceeded so well.

Sparky

[M3-SRT8]

HI,
As said above, modern amps have such low THD that it is of little practical use. However, if the distortion is high the amp will sound bad. To a repair tech, THD is very important.

Of more importance is to understand what the spec means and how is is measured. Doing this will add to your understanding of audio. A few years ago low THD was the primary problem faced by the engineers. We must give them a lot of credit to have suceeded so well.

Sparky

To answer your question, 'THD' is the total amount of measured distortion, from the Inputs to the speaker Outputs. In other words, 'total harmonic distortion' through the entire chassis. Best and tightest specs are measured @ 8 ohms, from 20-20kHZ, or, full bandwidth (or, wider frequencies).

LJB 8)

PS: Under ideal circumstances, most human beings cannot hear 3% ( ! ) distortion at their hearing range.

[Xander]

Also, when you get into bass and sub bass frequencies, most people won't ever notice up to 10% distortion.

[owdi]

Amplifier harmonic distortion does not matter much, because even an average amp has several orders of magnitude less distortion than the very best speakers.

For a speaker, an average -50db distortion between 20-20khz is common, and -60db is very very good. For an amplifier, -80db is achievable, even by a <$1k receiver. Preamps and DACs have even lower distortion than amplifiers.

Dan

[Briz vegas]

Amplifier harmonic distortion does not matter much, because even an average amp has several orders of magnitude less distortion than the very best speakers.

For a speaker, an average -50db distortion between 20-20khz is common, and -60db is very very good. For an amplifier, -80db is achievable, even by a <$1k receiver. Preamps and DACs have even lower distortion than amplifiers.

Dan

Unless it is a Quad 2905 Electrostatic. Hi Fi news measurements were
0.22% at 100 Hz
0,25% at 1 khz
1.36% at 10 Khz

These are test figures not the companies spin. This may be academic but its interesting none the less.

[dknightd]

My Dad Has 5 of those quads (well I lie, three of them are the same sized previous model - he tells me the new ones can provide a little more volume before arcing but otherwise sound similar). They are very nice sounding speakers. They benefit by the addition of subs (he uses 3 15" ones - he really should get two more so each channel is covered). You have to have the right room for these - they need a good amount of space behind them. But the room can't be too big if you want live concert volumes (apparently especially if you live at altitude).

[Johnloudb]

Noise + THD is very important. The ear is very sensitive to higher order harmonics such as 4th which is irritating. Second order harmonic distortion has a euphonic quality like that found in tube amps, and some Class D amps in the higher frequencies. The specs for the distortion spectrum are not published so best to use your ears to evaluate components when possible. Or reliable audio reviews.

[george_k]

The ear is very sensitive to higher order harmonics such as 4th which is irritating. Second order harmonic distortion has a euphonic quality like that found in tube amps, and some Class D amps in the higher frequencies.

What you say is not entirely true.

It's the odd order harmonics (3rd, 5th, 7th, etc) that the human ear finds irritating and even in the smallest amounts. Even order (2nd, 4th etc) harmonics on the other hand considered quite pleasant.

The degree of even and odd order harmonics is most dependent the type of circuit topology the designer chooses as well as the degree of negative feedback used at the output stages.

For instance the common push-pull amplifier design regardless of whether it's Tube or Transistor based produces more dominant odd-order harmonics and less pronounced even harmonics. The major difference between tube and transistor designs is that transistor designs tend to use a lot more feedback in order to improve things linearity, frequency response and harmonic distortion. The problem with negative feedback is that it further reduces the pleasant harmonics (even) and increases the unpleasant ones (odd).

That said, I agree that one should pick equipment based only on how it sounds and now what the specs say.

[Johnloudb]

What you say is not entirely true.

It's the odd order harmonics (3rd, 5th, 7th, etc) that the human ear finds irritating and even in the smallest amounts. Even order (2nd, 4th etc) harmonics on the other hand considered quite pleasant.

I agree with that. But, Sam Tellig (Stereophile) mentioned in a review of a single ended tube design, that adding feedback to it would cause the large amount of 2nd harmonic distortion to turn into very irritating 4th order. I just assumed he got that from a reliable source. Also, 2nd harmonic is the least offensive, as said by Nelson Pass.

I'm working on a 15Watt Class A circuit right now. Using only 4dB of negative feedback. And, in my spice sims, adding more feedback does increase the odd harmonic distortion like you say. You're welcome to take a look.

http://www.htguide.com/forum/showthread.php4?t=28342&page=4&pp=35