Regarded the thermal performance of heatsinks used in amplifiers (both if envelope resp. case is heatsink itself so as if separate internal alu profile is used), that is by typical hifi amplifiers, who has same output power as SAC (IGEL outfit), Densen or Naim Audio, that is much more lower. Examples from Luxman and NAD are to see here
http://www.audiostereo.pl/zalaczniki/907242_1.jpg
Luxman l-210 image by nanideleon on Photobucket
http://www.fmueller.com/images/NAD-3020.jpg
Nevertheless - for home hifi application there are not problems to be expected in most cases regarded too high values of temperature (Idle current <50mA). If I use only the typical vaues of acoustical output power, the needed electrical output power must be only present during the peaks in music material
If I use all kind of typical home audio amplifiers on stage (PA = public address) or at partys, they switch off after short time, if there are thermal protection, even by large output power values. In other cases I destroy the output stage. The main different between amps for home hifi and public address are the kind of cooling, not the max output power. Some of the old smart Luxman amps with alu profile heatsinks runs at +/-63V supply voltage, not lower as by a wide range of standart pa amps from Crest, Crown and many other.
This article is of interest in this case:
http://www.ferrotec.com/technology/thermoelectric/thermalRef05/
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Do you have a schematic that supports this claim?
If yes, please send me as pdf, gif or JPG attachement - thank you very much
....... bunch of bunyips .... they could have many faces .....
this
http://mx.geocities.com/drogommx/bunyip.jpg
or this
http://website.lineone.net/~deathwalker/art/bunyip.gif
or this ??
http://www.bunyipshow.org.au/BarneyBunyip1.jpg
You're entitled to your own opinion, but in mine, this is junk:
@GK!
I agree, something must have gone wrong the day this amp was designed.
Any DIYér regardles of experience, would turn his back on measurements like that, and start all over.
Distortion that high can never be overheard, so even if you did not use any THD+N measurings, or other design tools during development, a simple listening test would easily reveal this, one way or another.
What puzles me most though, is why the reviewer did not point this out thorougly.
But sometimes equipment designed in a basicly idiosyncratic way, emphazises certain sonic impressions. I.e. if you did play and mostly listened to distorted guitars, then some extra distortion would maybe make you feel better, although it is not correct.
Classical music would then in contrary be almost unbearable, which sometimes ,gently but unmisunderstandably, is pointed out in reviews of gear from this manufacturer.
To clear misunderstandings early and hopefully before they occur, I think it would be nice to dig a bit into the measuring standards used around the world.
I can only explain the IEC, maybe some others know about CEA 490A.
When you look a stated data from any manufacturer you might choose, these data was measured or calculated in respect of certain different relations. To make these data comparable, or at least understandable, standards are developed and maintained by often federal organisations or sometimes even private ones.
In Europe the measurement standard is called IEC, and their website can be visited here: IEC - International Electrotechnical Commission > INTERNATIONAL STANDARDS AND CONFORMITY ASSESSMENT . The American equivalent is found here: CEA - Consumer Electronics Association
In the following I will try to take you through the most important matters regarding measurement of output power of amplifiers for sound reproduction, the standard is named IEC 60.268-3, and is often renamed in most countries, i.e. ** 60.268-3 is the British Standard, which is completely the same as IEC. This is done the same way througout most of Europe.
Rated condition
The manufacturer states his data, which are called "Rated condition" and are to inform about:
Rated power supply (230/240V)
Rated source impedance
Rated source e.m.f. (which is the input voltage, compensated for voltage drops as a result of low input impedance)
Rated load impedance
THD or rated distortion limited output voltage or power
Rated mechanical and climatic conditions
This might make the data look like 100W @ 8 Ohm @ 0,5% THD @ 25 dgr. C @ 230V @ 1V input @ 100 Ohms with free airconvection.
Every single point of these data are to be fullfilled, both the manufacturer and the customer knows exactly what it is all about.
This was the rated data. IEC 60.268-3 point 3.1.2.
From these you extract a special condition called "standard measuring condition" This is a kind of preconditioning of the amplifier, as well as it also is to be used between every measurement, if conducted as a series of measurements.
This condition is never used for any output power measurement, but as a state of preparation and rest. The "standard measuring condition" is defined as "rated condition - 10dB refered to the input e.m.f."
This can be read about in IEC 60.268-3 point 3.1.3
Special conditions as i.e. position of tonecontrols, are to be specified clearly.
IEC also defines classes of operation, i.e. class A is defined as:
"In which the current in each active devise supplying the load current is greater than zero throughout each cycle of the signal for all values of load current up to and including the value determined by the rated output power or voltage and the rated load impedance"
In short it could be: bias = ½ peak current.
Output power:
There are several ways of measuring output power. First the manufacturer can stae almost anything, he just need to consider the matters mentioned above in "rated output power"
1 Distortion limited output voltage/power IEC 60.268-3 14.6.3.
2 Short term maximum output voltage/power
3 Long term maximum output voltage/power
4 Temperature limited output power
5 Sustaining time for rated distortion limited output voltage/power
The ones of interest to audiophiles and music lovers are the distortion limited output power and the temperature limited output power.
But i´ll try to explain them all.
Distortion limited output power: IEC 60.268-3 14.6.3
The voltage measured across the rated load impedance @ which the rated THD level is produced.
Distortion limited power P=U^2/R
Method of measurement:
The amp is preconditioned for 1 hour @ "standard measurement conditions"
The amp is brought under "rated conditions" with respect for all the conditions mentioned earlier.
The amp is operated under these conditions for 60 sec. then the source e.m.f. is readjusted to produce rated THD.
Output voltage is measured
Maybe repeated @ different frequencies if required.
Short term maximum output voltage/power IEC 60.268-3 14.7.2.
This is a test done with a tone burst signal @ 1KHz, and is done regardles of distortion. This is mostly to specify whether the output voltage is dangerous to humans or animals. The measurement is for only 1 sec.
So I will not dig any deeper into this.
Long term maximum output power IEC 60.268-3 14.7.3.
This is a measurement where the input e.m.f. is 10 times the rated input, creating massive overload, the signal is simulated program, the measurement is to be done 1 min. after the input signal is applicated.
Temperature limited output power IEC 60.268-3 14.7.4.
This is the interesting part.
To be specified is:
The output power which the amplifier is capable of supplying continuously, at a pecified ambient temperature, without exceeding the maximum permissible temperature in any component.
Special conditions as i.e. rackmounting are to be regarded.
Measurement is done as follows.
Amplifier is brought under "standard measurement conditions", except for the power supply, which is brought to the upper limit of the rated data i.e. 240V.
The ambient temperature shall be measured.
The source e.m.f. (input signal) is adjusted in steps to increase output voltage, each time waiting for temp. to stabilise. This procedure is repeated until one or more components reaches their temp ratings. i.e. junction temperature @ 150 dgr. or electrolytic caps @ 85 dgr. or so. If the amplifiers protection circuits are triggered, then the output voltage shall be measured @ the highest level possible, without interruptions.
The temp limited output power is then U^2/R
The amplifier is to work in this condition for 4 hours at least.
Sustain time for rated output power.
This is a duration test, where the amplifier is brought to "rated conditions" and then you basically wait for the distortion to rise or for an hour to pass, which ever is less.
These are the IEC measurements relevant for amplifier output power.
I´ve expained them from the Standard as faithfull as possible. I cannot give you any link to the standards, because they are copyrighted stuff, maintained by IEC. The standard is named IEC 60.268 Sound system equipment - part 3 Amplifiers.
To market amplifiers in Europe this standard is to be regarded, though the manufacturer must rate distortion limited output power, but can choose to rate the others if needed.
If nothing is rated or the rating for some parameter is missing, you can only do the temperature limited measurement, because output power without a corresponding THD percentage makes no sense.
I hope someone can enlighten us with the CEA490A standard for power measurement. That would be interesting.
Maybe we ought to start a new thread regarding measurements and standards.
I can only explain the IEC, maybe some others know about CEA 490A.
When you look a stated data from any manufacturer you might choose, these data was measured or calculated in respect of certain different relations. To make these data comparable, or at least understandable, standards are developed and maintained by often federal organisations or sometimes even private ones.
In Europe the measurement standard is called IEC, and their website can be visited here: IEC - International Electrotechnical Commission > INTERNATIONAL STANDARDS AND CONFORMITY ASSESSMENT . The American equivalent is found here: CEA - Consumer Electronics Association
In the following I will try to take you through the most important matters regarding measurement of output power of amplifiers for sound reproduction, the standard is named IEC 60.268-3, and is often renamed in most countries, i.e. ** 60.268-3 is the British Standard, which is completely the same as IEC. This is done the same way througout most of Europe.
Rated condition
The manufacturer states his data, which are called "Rated condition" and are to inform about:
Rated power supply (230/240V)
Rated source impedance
Rated source e.m.f. (which is the input voltage, compensated for voltage drops as a result of low input impedance)
Rated load impedance
THD or rated distortion limited output voltage or power
Rated mechanical and climatic conditions
This might make the data look like 100W @ 8 Ohm @ 0,5% THD @ 25 dgr. C @ 230V @ 1V input @ 100 Ohms with free airconvection.
Every single point of these data are to be fullfilled, both the manufacturer and the customer knows exactly what it is all about.
This was the rated data. IEC 60.268-3 point 3.1.2.
From these you extract a special condition called "standard measuring condition" This is a kind of preconditioning of the amplifier, as well as it also is to be used between every measurement, if conducted as a series of measurements.
This condition is never used for any output power measurement, but as a state of preparation and rest. The "standard measuring condition" is defined as "rated condition - 10dB refered to the input e.m.f."
This can be read about in IEC 60.268-3 point 3.1.3
Special conditions as i.e. position of tonecontrols, are to be specified clearly.
IEC also defines classes of operation, i.e. class A is defined as:
"In which the current in each active devise supplying the load current is greater than zero throughout each cycle of the signal for all values of load current up to and including the value determined by the rated output power or voltage and the rated load impedance"
In short it could be: bias = ½ peak current.
Output power:
There are several ways of measuring output power. First the manufacturer can stae almost anything, he just need to consider the matters mentioned above in "rated output power"
1 Distortion limited output voltage/power IEC 60.268-3 14.6.3.
2 Short term maximum output voltage/power
3 Long term maximum output voltage/power
4 Temperature limited output power
5 Sustaining time for rated distortion limited output voltage/power
The ones of interest to audiophiles and music lovers are the distortion limited output power and the temperature limited output power.
But i´ll try to explain them all.
Distortion limited output power: IEC 60.268-3 14.6.3
The voltage measured across the rated load impedance @ which the rated THD level is produced.
Distortion limited power P=U^2/R
Method of measurement:
The amp is preconditioned for 1 hour @ "standard measurement conditions"
The amp is brought under "rated conditions" with respect for all the conditions mentioned earlier.
The amp is operated under these conditions for 60 sec. then the source e.m.f. is readjusted to produce rated THD.
Output voltage is measured
Maybe repeated @ different frequencies if required.
Short term maximum output voltage/power IEC 60.268-3 14.7.2.
This is a test done with a tone burst signal @ 1KHz, and is done regardles of distortion. This is mostly to specify whether the output voltage is dangerous to humans or animals. The measurement is for only 1 sec.
So I will not dig any deeper into this.
Long term maximum output power IEC 60.268-3 14.7.3.
This is a measurement where the input e.m.f. is 10 times the rated input, creating massive overload, the signal is simulated program, the measurement is to be done 1 min. after the input signal is applicated.
Temperature limited output power IEC 60.268-3 14.7.4.
This is the interesting part.
To be specified is:
The output power which the amplifier is capable of supplying continuously, at a pecified ambient temperature, without exceeding the maximum permissible temperature in any component.
Special conditions as i.e. rackmounting are to be regarded.
Measurement is done as follows.
Amplifier is brought under "standard measurement conditions", except for the power supply, which is brought to the upper limit of the rated data i.e. 240V.
The ambient temperature shall be measured.
The source e.m.f. (input signal) is adjusted in steps to increase output voltage, each time waiting for temp. to stabilise. This procedure is repeated until one or more components reaches their temp ratings. i.e. junction temperature @ 150 dgr. or electrolytic caps @ 85 dgr. or so. If the amplifiers protection circuits are triggered, then the output voltage shall be measured @ the highest level possible, without interruptions.
The temp limited output power is then U^2/R
The amplifier is to work in this condition for 4 hours at least.
Sustain time for rated output power.
This is a duration test, where the amplifier is brought to "rated conditions" and then you basically wait for the distortion to rise or for an hour to pass, which ever is less.
These are the IEC measurements relevant for amplifier output power.
I´ve expained them from the Standard as faithfull as possible. I cannot give you any link to the standards, because they are copyrighted stuff, maintained by IEC. The standard is named IEC 60.268 Sound system equipment - part 3 Amplifiers.
To market amplifiers in Europe this standard is to be regarded, though the manufacturer must rate distortion limited output power, but can choose to rate the others if needed.
If nothing is rated or the rating for some parameter is missing, you can only do the temperature limited measurement, because output power without a corresponding THD percentage makes no sense.
I hope someone can enlighten us with the CEA490A standard for power measurement. That would be interesting.
Maybe we ought to start a new thread regarding measurements and standards.
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I forgot about this one:
Another measurement of interest to audiophiles is the long term tolerance of supply voltage variations.
This is not to be confused with power measurement, it is only a test to the amplifiers abillity to withstand variations in supply voltage.
This measurement is done @ the highest rated supply voltage i.e. 240V, and @ "standard measurement conditions". If temperature limited output power is rated by the manufacturer, this shall be the condition to which the amplifier is brought. The measurement has a duration of 4 hours, within which no component are to be hotter than its ratings. But also variations in gain, output level and hum are to be within certain limits.
Another measurement of interest to audiophiles is the long term tolerance of supply voltage variations.
This is not to be confused with power measurement, it is only a test to the amplifiers abillity to withstand variations in supply voltage.
This measurement is done @ the highest rated supply voltage i.e. 240V, and @ "standard measurement conditions". If temperature limited output power is rated by the manufacturer, this shall be the condition to which the amplifier is brought. The measurement has a duration of 4 hours, within which no component are to be hotter than its ratings. But also variations in gain, output level and hum are to be within certain limits.
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There's a simple explanation: some of those clowns claim the quality has nothing to do with distortions and in fact distortions can even be enjoyable. It happened before, it will happen again. For the right price, they'll enjoy whatever is shoveled down their thr... err... ars... err... ears.
I think you migh be right, about the reviewers.
But still I´ve only heard very few times, that exessive distortion was preferred over a more neutral reproduction. And even then listeners mostly agree witch one is the one with most distortion.
Btw. The distortion graphics GK published relates to an amplifier rated @:
125/250Watts @ 8/4 Ohms
@ 0,05% THD @ both 8/4 Ohms.
But already around 6 Watts it crosses the line to whole percentages of distortion @ 4 Ohms.
If that happened @ 100 Watts or higher, it would be of no serious concern, but 1% THD@ that power level is easily audible by anyone, as i.e. room acoustics and speaker behaviour will not mask distortion at that level. And one should remember, that this is into a pure resistive load. It will probably be much worse with a real life speaker connected.
This value is either created by a measurement error or by an individual error on that individual amplifiers. But I think more likely the first, because I have no confidence in the measured results of our well-known magazines here in Germany.
But in general, it would take a measuring method for measuring the behavior of amplifier, that provides all the results that I need to know how an amp sounds like without hearing it. But such a measuring method doesn't exist until this day.
Basicly there are 3 factors that affect the sound:
1) Power supply (mainly quality standart of transformer and capacitors, no possible of checking about simulation)
2) layout and GND (mass/earth) management (also no possible of checking about simulation)
3) the circuit topology itself (a wide range of measurements are possible about simulation, but I need reliable P-spice parameters)
Regarded the last factor of influence I note, that the classical and today's common THD measurements don't say anything about more or lower bad audible effects, because music signal mix isn't compare to 1 KHz sine wave.
If this would be not so, then it should never happen that e.g. an SE amp (Pass Zen, e. g. ) provides significantly better results than a classical AB amplifiers (mostly the topology of blameless amplifier from D. Self, sometimes also mirror symmetric topologies). But it is so, I think in all cases.
Please read in this case as carefully as possible following article from masterdeveloper Nelson Pass:
http://www.passdiy.com/pdf/zenamp.pdf
If I use classical and today's common THD measurements by simulation, I get tendencially also same results as by the practical measurements, but I don't find explantations, why the measurements do not correspond to the audible expressions (sense of hearing).
But I have try to find out different other measurement methodes at simulation aera and I'm almost (but not quite) shure that one thing is essential to investigate:
What happens to the sine wave signal at higher frequencies above the audible range:
Basicly, there are only two kinds of behaviors:
1) low pass character (level reduction, but no visual deformation to a sawtooth signal, even at 1 MHz and more)
Here is still a circuit topology to observe either without global NFB or with global NFB, but only one voltage gain stage in the feedback loop (Pass ZEN, Pass X-series, operational amplifier AD797, Densen, if the here showed schematic topology are correct and - also Dansk manufacture Thule Audio (topology from Anders Thule) - are some examples).
2) visual deformation to a kind of sawtooth signal - sometimes already above 20 KHz, independent of Cdom values - the vast number of commercial and DIY amplifier concepts are based on this (OP-AMP) topology, that include still two voltage gain stages with following power buffer and global non inverted NFB (unfortunately mostly non inverted mode).
The behavior about No 1 by an amplifier definitely still supply the better sound results by frequencies above approximately 300 Hz. Also If there are high levels of low order THD.
The behavior by an amplifier about No 2 is only useful by lower frequency aera because the higher internal open loop gain there is, i. e. useful only for bass transmission in active systems or multiamping systems at large loudspeakers.
Despite first-class values on the THD measurement, sound of such amplifiers by use for the upper frequency range or - as mostly use - in full range mode, is never really good, even by lowest simulated and measured THD values
I have posted some simulation results and explantations here to this topic - about follow URLs:
http://www.diyaudio.com/forums/pass...zero-o-os-0s-versus-later-aleph-versions.html
http://www.diyaudio.com/forums/pass...m-results-pass-x-series-us-pat-5376899-a.html
http://www.diyaudio.com/forums/pass-labs/147668-aleph-4-simulation-results-circuitmaker.html
http://www.diyaudio.com/forums/soli...screte-clone-comparison-seven-variations.html
http://www.diyaudio.com/forums/soli...-nfb-negative-feedback-me-wrong-question.html
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I don´t think you have to blame it on the germans this time
.It is audio precission measuring equipment that was used at the german magazine, and that is american, at least so far
If this measurement is done right or wrong, is hard to decide without repeating the measurements oneself. But actually I´ve listened to these amps, and these figures do not surprise me at all.
I think they are perfectly valid, otherwise the manufacturer would probably have made remarks on that matter, or at least not published the results on his own website.
But if they are true IEC values I do not know, only Stereophile are very thorough about explaining how they do their measurements.
This fulfill almost each used topology, "blameless" too, VAS is the only "voltage amplifying stage" in feedback loop, diferential input stage or follower output stage are not...The main problem of Densen "topology" is underbiased output in class B outside of (linearizing)feedback . Measurements at 10kHz or 19+20kHz IMD will be much worse.
From published graph is clearly visible, that output devices are switching off at about 400mW (rapid raising harmonics over third), measurements are done well..
In Germany they still think that B350 is a class A power amp, have a look yourself.
This is taken from this website today: http://www.connectaudio.de/densen/0496429bc90c37106/0496429c1a0d31f11/index.html
Price tag 7.500€ pair.
B-350 Technische Daten
Leistung 1 x 125W 8 Ohm / 1 x 250W 4 Ohm - im Class A Mode 40 Watt an 8 Ohm
Lautsprecheranschlüsse 2 Paar pro Kanal
Siebkapazität 750VA
Netzteil 100,000 Mikrofarad
Abmessungen 44,4cm x 31,0cm x 6,4cm
Erweiterbar mit Saxo Frequenzweiche
This is taken from this website today: http://www.connectaudio.de/densen/0496429bc90c37106/0496429c1a0d31f11/index.html
Price tag 7.500€ pair.
B-350 Technische Daten
Leistung 1 x 125W 8 Ohm / 1 x 250W 4 Ohm - im Class A Mode 40 Watt an 8 Ohm
Lautsprecheranschlüsse 2 Paar pro Kanal
Siebkapazität 750VA
Netzteil 100,000 Mikrofarad
Abmessungen 44,4cm x 31,0cm x 6,4cm
Erweiterbar mit Saxo Frequenzweiche
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I agree with first. This is one of the most doing work by other amps to improve the sonic quality (look at the other weblinks mentioned above)
By second I am not shure. For the class AB mode I haven't large aera for the choice of idle current. As I know, BjT output audio transistors in general mostly optimized for idle currents between 20 - 50 mA, independend of the used circuit driving topology. In this aera is the most smooth overtaken from ClassA to classB.
But a not mirror symmetric character (Ube-IC transfer) of the NPN-PNP devices could be the reason for the unwanted switching off and therefore enhanced H3 values (please note, there are some counterfeits on the marked - go to
Counterfeit Transistors. )
The second possibility it could be a idle current clearly below 20 mA. But in both cases I have an individual error, as I mentioned above.
Kurt von Kubik: Class A mode 40 Watt at 8 Ohms - misleading, but difficult to refute, since ambiguous. If one were to say, 1A idle current through the output power stage, you can do against it if it is not true and it is clearly to verify - hard but real.
If you unsatisfy with the sound of your Densen, you can send me for checking
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Class A is a very well defined state of operation.
IEC 60.268-3 point number 4 clearly states the definition of class A, B, AB, D and so forth.
There is nothing to question what so ever, no ambiguousnes present at all.
The funny thing really is, that every audio component @ any price works as a class A amplifier, except output amplifiers.
Class A is the most common mode of operation in audio equipment, with the exception of poweramplifiers.
