Ok, with the consistent listeners, did you ask for and get descriptions/reasons for their preferences ?.
Dan.
These are Sales figures so easily confirmed and not open to Golden Pinnae debate.
The Best seller was also designed by my R&D Dept. but not by me. If you were in the trade at that time, it should now be obvious what these models are 😀
Originally Posted by ontoaba
No feedback type is easier to reach more plesant sound, but harder to reach better sounded amp.
If your friend best amp is non feedback, he may like pleasant more than beauty.
In fact of the matter that my friend as a professional sound engineer high-end well-versed in the sound and worked his way up from the tube amp transistor . He tried almost everything you can imagine : and amplifiers with electromechanical feedback , and a high output impedance , and the output stage in pure class A. In the last step he made hybrid amps - tube driver and transistor output stage . But when he made a comparison of his best sound amplifier with an amplifier with a negative output impedance before he realized that it just wasted time on the study of different designs amplifiers.
Amplifier with a negative output impedance provides the most accurate control of the speaker cone movement , and hence the most natural sound compared with other amplifiers .
regards
Petr
No feedback type is easier to reach more plesant sound, but harder to reach better sounded amp.
If your friend best amp is non feedback, he may like pleasant more than beauty.
In fact of the matter that my friend as a professional sound engineer high-end well-versed in the sound and worked his way up from the tube amp transistor . He tried almost everything you can imagine : and amplifiers with electromechanical feedback , and a high output impedance , and the output stage in pure class A. In the last step he made hybrid amps - tube driver and transistor output stage . But when he made a comparison of his best sound amplifier with an amplifier with a negative output impedance before he realized that it just wasted time on the study of different designs amplifiers.
Amplifier with a negative output impedance provides the most accurate control of the speaker cone movement , and hence the most natural sound compared with other amplifiers .
regards
Petr
Much of this is true, but I don't believe it is the whole story. It is true that there is a law of diminishing returns in seeking extremely low measured distortion. It is also true that a nonlinear load will of course cause the output of the amplifier to be distorted to some extent if the output impedance is non-zero. This last observation is valid for any amplifier, whether it be with or without NFB, and whether it be tube or solid state. If anything, this might suggest that distortions due to nonlinear loads might be higher for No-NFB and tube amplifiers.
Its also important to recognize that the distortions of the nonlinear load of a loudspeaker are quite "soft" in nature (not of high order). This can be in contrast to some amplifier distortions like crossover distortion. Often the major nonlinearities in a speaker load are at low frequencies where woofer excursions through the gap and mild saturation of the larger crossover inductors come into play. At mid and high frequencies the nonlinearity of the speaker load is not that bad if the levels are not really high.
Cheers,
Bob
Not like that.
I am sure my amp is much faster than those audio-pro. It is not just in amplifier feedback loop, but crossover is also changes the sound, even an output filter and HF RC damper.
Could you point me to that negative output impedance amp? May be he has problem with fatiguing phenomena.
Attachments
its beginning to read like a general discussion area. Should we change the title so it isn't misleading any new comers? Or does it mean the CFA design pro-con investigation is done and we learned what we wanted to.
-Richard Marsh
-Richard Marsh
The main effect of negative output impedance is to lower the Qt in box of the speaker.
Robert Munnig Schmidt in Linear Audio, volume 6, pp 33-46, provides some data : it did not found that it does much for distortion reduction and better control of the cone movement.
forr > The only time delay in a feedback loop is due to the travel of the current through a few cm at the velocity of 300000 km/s.
ontoaba > Not like that.
So, what do you mean by "damping-timing or delayed interaction of speaker-amplifier" ?
ontoaba > Not like that.
So, what do you mean by "damping-timing or delayed interaction of speaker-amplifier" ?
The title is CFA Topology guys... can you take this other highly exciting and entertaining subjects to the appropriate forum/thread?
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I measured the THD at 1 kHz, 3.6 Vrms, of the Renardson Mosfet amplifier. Extremly low distortion in all cases :
no load H2 = -133 dB, H3 = -129 dB, THD = 0.00011%
8 Ohm H2 = -132 dB, H3 = missing data, THD = 0.00013%
16.8 µF H2 = -131 dB, H3 = -127 dB, THD = 0.00012
1.5 mH H2 = -132 dB, H3 = -130 dB, THD = 0.00011%
Good amplifiers have no difficulty to handle reactive loads.
What is the distortiometer able to give-you such numbers ?
Because, if it is simulator, it is just amusing fairy tail and, anyway, don't take care of real speakers behaviors adding complex signals in the feedback loop. The combination of them with the original signal- the error amp signal can ask unexpected slew rate, much higher than the requisite for the signal itself.
An externally hosted image should be here but it was not working when we last tested it.
But, as says Richard, let's go back to CFAs designs and their slew-rate benefit.
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Simulators do not measure, they estimate. When used to estimate the harmonic distortion of full amplifiers, the results are very boring.
Here the tools I used :
Distorsion meter : Cyril Bateman's
Capacitor Sounds, Speaker Cables and Crossover Inductors.
Amplifier : Mike Renardson's, no differential ou complementary pair input (it's a reverting amp)
MJR7-Mk5 Mosfet Power Amplifier
By the way, can the discussion include inverting amps with complementary pair input similar to those of the CFAs mostly discussed here ?
They are very few, currently the name which comes to my mind is ETI's Stan Curtis class A amp, aimed at DIY :
Stan Curtis, Engineer, The Lecson AP4 and ETI Class A amplifiers
The same input stage has been found in british amps Lecson and Mission.
I don't quite understand why "real speakers behaviors adding complex signals in the feedback loop' needs to be particularly "taken care of". It seems this has been viewed as a "bad" thing.
Can it be viewed the other way around, as an indication of the feedback amp being exactly in the process of correcting the misbehavior of the speaker, or the speaker is indeed being taken care of exactly at the moment the "real speakers behaviors adding complex signals in the feedback loop"? Isn't this a more systematic view?
What was the amp that was driving the speaker under the test when that waterfall plot was taken, with or without feedback? Do you have both plots, w/ and w/o F/B to compare?
Can it be viewed the other way around, as an indication of the feedback amp being exactly in the process of correcting the misbehavior of the speaker, or the speaker is indeed being taken care of exactly at the moment the "real speakers behaviors adding complex signals in the feedback loop"? Isn't this a more systematic view?
What was the amp that was driving the speaker under the test when that waterfall plot was taken, with or without feedback? Do you have both plots, w/ and w/o F/B to compare?
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I could'nt edit my previous post. So I add this :
The distortion numbers per se are not so important, it is the modification of distortion between no load and different kinds of load which is.
I choose an output voltage around 4 Vrms because it is the value I many times found the most critical for amps, well above noise and where the crossover problems can be better detected
If the amp is far from current limits, higher output voltages usually show lower distorsion.
The distortion numbers per se are not so important, it is the modification of distortion between no load and different kinds of load which is.
I choose an output voltage around 4 Vrms because it is the value I many times found the most critical for amps, well above noise and where the crossover problems can be better detected
If the amp is far from current limits, higher output voltages usually show lower distorsion.
Not cable delay. Do not assume that there is only cable at ampifier, loudspeaker and between them. Also do not assume that amplifier with 1ppm distortion any load in singletone is perfect that won't distort the loudspeaker wave output.
@Richard
Sorry for off topic. But, I don't think that very high slewrate is a benefit at loudspeaer driving.
ontoaba
Could you point me to that negative output impedance amp? May be he has problem with fatiguing phenomena.
Amplifier with a negative output impedance provides the most precise control over the movement of the diffuser. Therefore, this amplifier provides the closest match to the natural sound.
You exhausting natural sounding favorite musical instrument? Here is the answer to your question.
best regards
Petr
Could you point me to that negative output impedance amp? May be he has problem with fatiguing phenomena.
Amplifier with a negative output impedance provides the most precise control over the movement of the diffuser. Therefore, this amplifier provides the closest match to the natural sound.
You exhausting natural sounding favorite musical instrument? Here is the answer to your question.
best regards
Petr
No, now it sounds like VFA, global loop feedback haters coming out of the woodwork
and loading on all of the traditional silliness as not applying to CFA
do we really have to reprise all of the ca 1980 JAES findings re Otala and fanboys "suspicions" which have been proved conceptually flawed or irrelevantly low, easy to overcome without his tweak recommendations?
The output impedance “interface distortion” comments should make any competent engineer blush – Cordell, Self “textbook” audio amp theory and measurements, JAES articles by Cherry, et al
look on Klippel's site if you are serious about bounding dynamic speaker electrical terminal nonlinearities
but you also need to tighten up your reasoning about said speaker impedance distortion and which type amps reject it better
almost everything about an amplifier's output at audio frequencies into complex speaker loads can be seen with a "tug-of-war" test - a (bigger) amp on the other end of a power R load - driven with phase shifted test signal
you can also drive the other end of the power R with different frequencies, multi-tones, emulate nonlinear loads
and loading on all of the traditional silliness as not applying to CFA
do we really have to reprise all of the ca 1980 JAES findings re Otala and fanboys "suspicions" which have been proved conceptually flawed or irrelevantly low, easy to overcome without his tweak recommendations?
The output impedance “interface distortion” comments should make any competent engineer blush – Cordell, Self “textbook” audio amp theory and measurements, JAES articles by Cherry, et al
look on Klippel's site if you are serious about bounding dynamic speaker electrical terminal nonlinearities
but you also need to tighten up your reasoning about said speaker impedance distortion and which type amps reject it better
almost everything about an amplifier's output at audio frequencies into complex speaker loads can be seen with a "tug-of-war" test - a (bigger) amp on the other end of a power R load - driven with phase shifted test signal
you can also drive the other end of the power R with different frequencies, multi-tones, emulate nonlinear loads
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Why don't you try to figure out by yourself with an oscillo at the VAS input, comparing the same amp, with the same square waves under resistive and real speakers load ?
It is an interesting experience.
I missed there which speaker you connected for your measurements. Should I assume the above means you used resistors, inductors and capacitors rather than a real-world load?