Third harmonic distortion

The 0.1% THD is a quality consumer audio. The 1% is low end.

Vladimir Vassilevsky DSP and Mixed Signal Design Consultant

Zero.

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-- Many thanks,

Don Lancaster voice phone: (928)428-4073 Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552 rss:

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I hope you realize that THD means *Total* Harmonic Distortion.

.1% is easily good enough. You're unlikely to hear anything much less than

It can depend. For normal amplifier topologies which produce mostly low order harmonic distortion, I'm sure the numbers that Vladimir has quoted are representative. However, if the distortion is non-harmonic (IMD), or higher order, quite low levels can be much more obnoxious.

Indeed... my standard test is to play a Mozart wind ensemble that includes oboe... really demos the IMD :-( ...Jim Thompson

"HardySpicer"

THD at what level, full power or 1 watt ?

THD at what frequency ?

If in the tuner, at what modulation depth ?

.... Phil

THD is not "Third Harmonic Distortion".

In audio parlance, THD is "Total Harmonic Distorion".

Sheesh.

"Sum Ting Wong"

BTW:

THD figures include any noise or hum.

.... Phil

PARD on em wahh! heheh

One should also ask, where is that distortion produced, in the signal processing and power amplifier stages or is it due to bad amplitude/phase response in the IF filter stages.

Cutting the higher order Bessel sidebands from the signal will introduce some distortion, especially at higher ultrasonic audio frequencies (stereo multiplex difference signal). The distortion characteristics is different from for instance typical power amplifier distortion (in which 0.1 % might be objectionable).

Of course, the problem with IF filter design, is to find a compromise between phase and amplitude response and adjacent channel rejection. A selectable IF bandwidth would help, but that is rarely an option in the real world.

"Ralph Barone"

If there is enough of one to be heard, the other will be too.

.... Phil

You are confusing SINAD and THD. THD does not include noise or hum. Depending on the gear you own, most read SINAD and not THD. That is if you notch the fundamental and measure the residual, that is SINAD. THD requires knowing the levels of all the harmonics.

Seriously Phil, why do you bother answering questions where you are clueless, which is always the case, then follow it up with cursing when somebody like me bitch slaps you for your blatant ignorance of the facts.

Regarding the original question, getting 1% on a FM broadcast in real life is doing good. Multipath is not your friend. The higher end tuners have selectable IF BW, with wider being lower THD. Top of the line tuners are doing about 0.25%, but that is a bench test.

I've concluded that if you can get a decent stream on your station of interest, something like a Squeezebox is far better in real life. Even

"A" vile, autistic pig, not "an" vile.

Yes. An anvil(e) is something many wish would fall on your thick skull.

More proof that you are inept at being an adult.

As the wise man said, "What we have here is a failure to communicate."

To an old-time audio guy, THD is what he reads on the scale of his THD meter. I have an HP 339A THD meter, and it works as Phil says--it uses a bridge to notch out the fundamental, and has an old-fashioned true RMS meter that indicates THD. If that's the definition used in the field, you gotta use that, whether or not it's the one used in yours. (Physicists use the opposite Fourier transform sign convention to EEs, i.e. in physics, a lagging phase is positive, so I'm used to this.)

I also have an HP 35665A dynamic signal analyzer, and it computes THD your way, i.e. it looks for a sequence of N harmonic peaks and adds up the power in peaks {2...N}.

An RF or data converter guy thinks of THD as being different from SINAD, but that's because his stuff comes out as a digital stream he can perform an FFT on.

Cheers

Phil Hobbs

" Phil Hobbs "

The bandwidth of a THD meter is normally sufficient to allow the 5th harmonic of 20kHz to register within -3dB and any noise within this band is included in the reading.

Such meters have been used to specify the THD of audio gear of all kinds for many decades and the reading is quoted as a percentage of the output voltage.

Nothing fundamental has changed in relation to THD specs with the exception of the percentage figure being more often quoted as a negative dB when professional gear is concerned.

Recently, one sees the term " THD + N " being used, simply to avoid any doubt.

BTW:

I regularly make THD measurements on audio gear, including just yesterday.

A 300 wpc mosfet power amp tested 0.005% THD at 1kHz at 8 ohms.

.... Phil

snip

Excellent post.