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Topic: Total harmonic distortion

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	Total Harmonic Distortion
		The levels of harmonic distortion in a high quality amplifiers are sooooo far below audibility that they are basically of no concern.
		When someone tells you that one amplifier is definitely going to sound better because its THD is rated at.002% vs an amp with.05%, you can be pretty sure that he doesn't know what he's talking about.
		When the harmonics reach 5%, they are clearly audible.
	www.bcae1.com /thd.htm (439 words)

	SoundStage! Measurements - How we test amplifiers
		This section indicates the power output of the amplifier at 1% and 10% distortion levels and 8-, 4-, and 16-ohm impedances when the amplifier is driven by a 1kHz test signal.
		What it tells you: Three or four measurements are displayed: 1kHz total harmonic distortion plus noise vs power output for 16-, 8-, and 4-ohm resistive loading on the 8-ohm tap for tube power amplifiers, plus SMPTE IM distortion with 8-ohm loading on the 8-ohm tap.
		What it tells you: Four measurements are displayed here: Total harmonic distortion vs frequency at four power levels ranging from 1W to a value at or near the rated power of the amplifier.
	www.soundstagemagazine.com /measurements/test_amplifiers.htm (925 words)

	R.E. Designs FAQ's
		What they found was that the human ear is very insensitive to harmonic distortion that is close to the main signal, and increases in sensitivity to harmonic distortion further away from the main signal.
		The second harmonic, which is an octave away from the main signal, is the hardest to hear, especially when you are driving a loudspeaker.
		If the sum total distortions were farther away from the main signal you would be able to hear it.
	www.redesignsaudio.com /faqs.html (4610 words)

	Sennheiser Wireless Headphones
		Designed with a special diaphragm geometry to reduce intermodulation distortion, and a comressed cellulose fleece to reduce THD.
		Total Harmonic Distortion(THD) less than or equal to 0.1%!
		Great for hearing the harmonic sparkle of string instruments such as violins, guitars, even concert grand pianos.
	www.microphoneheaven.com /headphones.html (535 words)

	THD - Total Harmonic Distortion measurement
		where terms 2..N are the power levels of the harmonics and term 1 is the power level of the fundamental (the pure tone).
		In normal measurements (with low THD and THD+N) the 2 methods will give identical results, since more than 99% of the measured energy is always contained in the fundamental harmonic (H1).
		The IMD value is computed as the ratio of the sum of the power levels of the intermodulation harmonics to the sum of the power level of the two strongest tones.
	www.purebits.com /appnote8.html (751 words)

	Harmonic distortion
		THD is measured by subtracting the original input sound from the distorted sound in a way that a signal with only the distortion is generated.
		Another early example of use of harmonic distortion is the heavily overdriven Hammond organ sound, often combined with Leslie speaker cabinets, as used in the psychedelic music of the late sixties in the twentieth century.
		Especially on chords or loops it is often important that a harmonic distortion circuit does not produce a lot of extra energy in the highest parts of the spectrum, as this will lead to problems in a mix with vocals and acoustic instruments and/or destroy the sense of spaciousness in the overall sound.
	www.xs4all.nl /~rhordijk/G2Pages/HrmDistortion.htm (3749 words)

	Science Fair Projects - Total harmonic distortion (Site not responding. Last check: )
		The total harmonic distortion, or THD, of a signal is a measurement of the harmonic distortion present, that is, any departure of the output signal waveform from that which should result from the input signal waveforms being operated on by the system's specified or ideal transfer function.
		This is a measurement of the extent of that distortion.
		The THD is usually expressed in percent as distortion factor or in dB as distortion attenuation.
	www.all-science-fair-projects.com /science_fair_projects_encyclopedia/Total_harmonic_distortion (411 words)

	PowerPedia:Amplitude distortion - PESWiki
		The total harmonic distortion, or THD, of a signal is a measurement of the harmonic distortion present and is defined as the ratio of the sum of the powers of all harmonic components to the power of the fundamental.
		THD is a measurement of the extent of that distortion.
		Intermodulation distortion is nonlinear distortion characterized by the appearance, in the output of a device, of frequencies that are linear combinations of the fundamental frequencies and all harmonics present in the input signals.
	peswiki.com /index.php/Amplitude_distortion (1093 words)

	Glossary: THD (Total Harmonic Distortion) \| Sweetwater.com
		The ratio of the power of the fundamental frequency at the output of a device versus the total power of all the harmonics in the frequency band at the output of the device.
		The simplest form of this distortion is the addition of harmonics to the outputted signal.
		THD represents the sum of all the harmonics added by a device as a percentage of the level of the signal being measured.
	www.sweetwater.com /expert-center/glossary/t--THD (233 words)

	Audio Specifications
		Total harmonic distortion (THD) is then defined as the ratio of the rms voltage of the harmonics to that of the fundamental component.
		Hopefully, it's obvious to the reader that the THD of a 10 kHz signal at a +20 dBu level using maximum gain, is apt to differ from the THD of a 1 kHz signal at a -10 dBV level and unity gain.
		As with harmonic distortion measurement, this is done with a spectrum analyzer or a dedicated intermodulation distortion analyzer.
	www.rane.com /note145.html (5215 words)

	OilOnline - The Original Online Source for the Oil Industry
		The total harmonic voltage distortion (or VTHD) at the Lineator terminals was measured at 2.2% and 2.7% respectively for the port and starboard Lineators at 85% ROV kW loading.
		Harmonic currents are unwanted multiples of the fundamental (50Hz or 60Hz) current which interact with the supply impedances to produce voltage distortion.
		As harmonic distortion is 'steady state' and continuous the issue of electrical power quality associated with harmonics not only raises safety concerns but also adversely affects the performance and reliability of marine plant and equipment.
	www.oilonline.com /news/features/oe/20060207.Homing_i.20334.asp (1545 words)

	Station Information - Total harmonic distortion
		Total harmonic distortion (THD): Of a signal, the ratio of (a) the sum of the powers of all harmonic frequencies above the fundamental frequency to (b) the power of the fundamental frequency.
		Note 1: The THD is usually expressed in dB.
		Note 2: Measurements for calculating the THD are made at the output of a device under specified conditions.
	www.stationinformation.com /encyclopedia/t/to/total_harmonic_distortion.html (75 words)

	Analog Devices: Analog Dialogue: Ask The Applications Engineer - 13
		Harmonic distortion is measured by applying a spectrally pure sine wave to an amplifier in a defined circuit configuration and observing the output spectrum.
		Harmonic distortion may be measured by looking at the output spectrum on a spectrum analyzer and observing the values of the second, third, fourth, etc., harmonics with respect to the amplitude of the fundamental signal.
		Harmonic distortion may be expressed individually for each component (usually only the second and third are specified), or they all may be combined in a root-sum-square (RSS) fashion to give the total harmonic distortion (THD).
	www.analog.com /library/analogDialogue/Anniversary/13.html (2030 words)

	MTE Corporation - Economical Solutions to Meet Harmonic Distortion Limits
		Harmonic currents are thus attenuated by the inductive reactance of the input reactor.
		It is now very simple to perform harmonic analysis on a power system, because we know the worst case levels of harmonic distortion whether we are employing a line reactor, combination of line reactor and DC link choke, or broad band harmonic suppressor.
		When harmonic filters are applied at the facility input transformer, the utility benefits from the harmonic reduction but the harmonic current will still be flowing on the facility conductors and mains.
	www.mtecorp.com /harmsol.html (2283 words)

	MTE Corporation - MTE Corporation Information Desk
		A harmonic is a component of a periodic wave having a frequency that is an integral multiple of the fundamental power line frequency of 60 Hz.
		Harmonic current distortion limits at the PCC are set by the ratio of short circuit current to load current.
		The percent of harmonic distortion at the point it is generated (at the VSD) times the percent the nonlinear load represents of total which equals the percent of total harmonic distortion at the point of common coupling (PCC).
	www.mtecorp.com /nr_success_story.html (2134 words)

	Distortion Analyser
		Total harmonic distortion (THD) measurements are one of the most commonly quoted in audio.
		The distortion shows up as a signal that is harmonically related to the signal fed into the amp, but is not the fundamental.
		The distortion waveform is very important - a low average level spiky waveform (typical of crossover distortion) will sound much worse than an apparently higher level of "clean" 3rd harmonic distortion from a well designed push-pull amplifier stage.
	sound.westhost.com /project52.htm (2052 words)

	Total Harmonic Distortion (SimPowerSystems) (Site not responding. Last check: )
		The THD is defined as the root mean square (RMS) value of the total harmonics of the signal, divided by the RMS value of its fundamental signal.
		It follows that the THD is null for a pure sinusoidal voltage or current.
		Connect to the first input the voltage or current you want to measure the total harmonic distortion.
	www.weizmann.ac.il /matlab/toolbox/powersys/totalharmonicdistortion.html (120 words)

	Audio DesignLine \| Audio in the 21st Century - Part 12
		Harmonic distortion is typically not de-sired behavior, but a side effect of being con-strained to using a finite number of imperfect com-ponents.
		The first odd harmonic is the third harmonic, which usually has the highest ampli-tude of all the odd harmonics in the context of har-monic distortion.
		THD is practically measured by taking the dis-torted output signal and removing the fundamental input signal from it.
	www.audiodesignline.com /193600476?cid=RSSfeed_audiodesignline_adlRSS (679 words)

	Total Harmonic Distortion (SimPowerSystems) (Site not responding. Last check: )
		Measure the total harmonic distortion (THD) of a signal
		The Total Harmonic Distortion block measures the total harmonic distortion (THD) of a periodic distorted signal.
		The frequency, in hertz, of the fundamental signal.
	www.technion.ac.il /guides/matlab/toolbox/powersys/totalharmonicdistortion.html (120 words)

	Bringing harmony to power
		Harmonic distortion is measured in terms of percent of the fundamental.
		Total harmonic distortion, the ultimate characteristic, is the ratio of the root mean square (RMS) sum of the harmonics to the fundamental.
		Total harmonic distortion can refer to the quality of the input current drawn by a piece of equipment or the quality of the AC power source feeding that equipment.
	telephonyonline.com /mag/telecom_bringing_harmony_power (2616 words)

	total harmonic distortion Resources (Site not responding. Last check: )
		...total harmonic distortion (THD) total harmonic distortion (THD): Of a signal, the ratio of (a) the sum of the powers of all harmonic frequencies...
		Total Harmonic Distortion: When an amplifier is driven with a signal, the output of the amplifier is an...
		The levels of harmonic distortion in a high quality amplifiers are sooooo...
	www.techrectory.com /Computational/directory/total-harmonic-distortion.html (235 words)

	Harmonic Distortion Analysis in LabVIEW 6i- Developer Zone - National Instruments
		THD is a measure of the energy contained in the harmonics of a signal, as compared to the energy contained in the fundamental.
		Due to the change in the method of computing the THD and the amplitudes of the harmonics, expect to see some differences in their typical output values if you switch from using arrays and the THD VI to using the waveform data type and the Harmonic Distortion Analyzer VI.
		The THD VI outputs the harmonics, including the fundamental, array in Vrms, whereas the Harmonic Distortion Analyzer VI outputs the array of harmonics, including DC and the fundamental, in peak amplitude units, i.e.
	zone.ni.com /devzone/cda/tut/p/id/3400 (1827 words)

	THD Measurement and Conversion
		There are several weaknesses to this approach: not all harmonics are equally discordant; even harmonics tend to be much less dissonant then odd ones; higher harmonics are generally considered more dissonant; and a percentage number does not necessarily relate to how the ear perceives sound and distortion.
		While this apparent THD figure is, indeed, representative of the total power of the harmonic content, we still have to convert this power to an equivalent RMS voltage in order to come up with a THD figure according to standard methodology.
		So the correct answer is obtained by taking total harmonic power (0.0425 watts) and calculating the equivalent RMS voltage, given by the square root of power times output impedance, or about 0.583 volts in the example.
	www.dogstar.dantimax.dk /tubestuf/thdconv.htm (1180 words)

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