yes, "outlier" is a good term to describe this clear-cut difference, it being understood that I'm refering to all the amps I've had/have for test at home (or still own). Can't speak for "most amplifiers" (on earth) of course.
Ah,
Can we talk about the unmeasured issue? How is damping factor measured?
The basic technique is simple. You connect a resistor between the two outputs of an amplifier. The resistor is typically 8 ohms. You then drive one channel with a sine wave signal and let the other output try to maintain zero volts. If you drive with ten volts and measure .1 volt on the other channel the damping factor is 100. You can then sweep the frequency to get a plot of damping factor vs frequency.
HOWEVER this is for a single output voltage! You could also use a single frequency and sweep the voltage to measure damping factor vs level. This is not done because the assumption is that damping factor is influenced by feedback and feedback declines with frequency. So that a rising damping factor is expected.
BUT even with feedback there is a finite impedance that the feedback is effectively reducing to create the damping factor. At some point the amplifier under test runs out of current capability to reduce the signal being forced in. At that point feedback has lost its' power to reduce the output voltage.
All of the large professional linear power supply Crown amplifiers have very low source impedance (meaning high peak current) power supplies. The use extra thick power supply busses. They often have extra copper besides the PC card coating to distribute the current and keep the available current high.
So two amplifiers with the same power rating and damping factor will behave differently at high power damping.
Now I am quite comfortable when SY tells me he can't hear the difference. He can even insist that in a controlled test "X" number of subjects cannot hear a difference. But there are design decisions in those amplifiers that do result in measurable peak current differences and it must be a complete coincidence that folks regard amplifiers with low power supply impedance as having better base response.
I once measured Crown MA5000s driving HF compression drivers putting out a bit more than 110 amps into the load. (Tek THS720P scope & current probe on site.)
ES
Can we talk about the unmeasured issue? How is damping factor measured?
The basic technique is simple. You connect a resistor between the two outputs of an amplifier. The resistor is typically 8 ohms. You then drive one channel with a sine wave signal and let the other output try to maintain zero volts. If you drive with ten volts and measure .1 volt on the other channel the damping factor is 100. You can then sweep the frequency to get a plot of damping factor vs frequency.
HOWEVER this is for a single output voltage! You could also use a single frequency and sweep the voltage to measure damping factor vs level. This is not done because the assumption is that damping factor is influenced by feedback and feedback declines with frequency. So that a rising damping factor is expected.
BUT even with feedback there is a finite impedance that the feedback is effectively reducing to create the damping factor. At some point the amplifier under test runs out of current capability to reduce the signal being forced in. At that point feedback has lost its' power to reduce the output voltage.
All of the large professional linear power supply Crown amplifiers have very low source impedance (meaning high peak current) power supplies. The use extra thick power supply busses. They often have extra copper besides the PC card coating to distribute the current and keep the available current high.
So two amplifiers with the same power rating and damping factor will behave differently at high power damping.
Now I am quite comfortable when SY tells me he can't hear the difference. He can even insist that in a controlled test "X" number of subjects cannot hear a difference. But there are design decisions in those amplifiers that do result in measurable peak current differences and it must be a complete coincidence that folks regard amplifiers with low power supply impedance as having better base response.
I once measured Crown MA5000s driving HF compression drivers putting out a bit more than 110 amps into the load. (Tek THS720P scope & current probe on site.)
ES
How does that jibe with the poster's insistence that this difference can be heard at 1 watt?
No-one disputes that power delivery is vital in sound reinforcement, and I even made that point several times in this thread.
Classic audiophile gambit, Bear. Anyone who disagrees with you is "Mid-fi".
Another study that comes to mind is the one commissioned by Quad where their listeners couldn't tell the difference between the Quad II, 303 and 405 power amps.
The only explanation I can think of for the issue at hand (other than experimenter expectancy) is that the Crown generates a bunch of crossover distortion at low power and that makes it sound "hard" and "lean", which are at a similar end of the sonic spectrum to "tight" and "punchy". When designing a bigass PA amp it is very tempting to cool the bias down and throw feedback at the resulting crossover gain dip. Peavey didn't even bother to include a bias trim in many of their solid-state modules.
Another study that comes to mind is the one commissioned by Quad where their listeners couldn't tell the difference between the Quad II, 303 and 405 power amps.
The only explanation I can think of for the issue at hand (other than experimenter expectancy) is that the Crown generates a bunch of crossover distortion at low power and that makes it sound "hard" and "lean", which are at a similar end of the sonic spectrum to "tight" and "punchy". When designing a bigass PA amp it is very tempting to cool the bias down and throw feedback at the resulting crossover gain dip. Peavey didn't even bother to include a bias trim in many of their solid-state modules.
What does this challenging question have to do now ?
I created this post to seek explanations from others who might have experience and more technical knowledge than me, and who have also made similar experience with this amp or family of amps.
No one is forcing you to share the starting point about this amp or family of amps (a claim that they have a special "slam") and if you disagree, you may of course wish to consider passing your way to other threads instead of imposing your sarcasm.
This thread went quite well up to recently and I now appologize to other readers for reacting like this.
I kindly invite you to take a sec and to look at your own various posts in the present thread, which are not contributing to anything but sarcasm.
Ummm, I was unaware that I personally needed to have peer reviewed publications on this subject in order to identify weaknesses in published papers? Is this a requirement? Why not address the actual concerns?
This is a bit like the cold fusion stuff, with respect to the ability to replicate the results. No replication possible due to the uniqueness of the test conditions AND that the test conditions are not properly enumerated ( a big word meaning simply 'explicitly stated')??
Classic audiophile gambit, Bear. Anyone who disagrees with you is "Mid-fi".
Another study that comes to mind is the one commissioned by Quad where their listeners couldn't tell the difference between the Quad II, 303 and 405 power amps.
The only explanation I can think of for the issue at hand (other than experimenter expectancy) is that the Crown generates a bunch of crossover distortion at low power and that makes it sound "hard" and "lean", which are at a similar end of the sonic spectrum to "tight" and "punchy". When designing a bigass PA amp it is very tempting to cool the bias down and throw feedback at the resulting crossover gain dip. Peavey didn't even bother to include a bias trim in many of their solid-state modules.
No, incorrect. You've used a classic debating trick here.
I did not say or imply that any person who holds a different point of view is anything, including "mid-fi".
It is trivial to set up "tests" where listeners can not "hear the differences". Beyond simple. Need it be explained?
Anyone, show me a single "peer reviewed paper" on these tests where the THD or IM of the speaker(s) and/or the tweeters were tested during and after the tests, including at and over the average test SPL level?? No?
Why is this not tested?
Is it not clear that this sort of thing will be an important factor in what can and can not be reproduced??
So, by way of analogy, I play a 4k video source but use a monitor that is only 640 wide? Whoa! can't tell the difference between 4k and 1080 source? No kidding...
If you don't get the whole thing pretty darn clean, you're going to not be able to hear many things, especially differences between otherwise pretty good amps...
_-_-
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So you're admitting that distortion from amps is insignificant compared to distortion from loudspeakers? Well, that is ground that I can agree on. Do you know of any loudspeakers that generate less distortion than a good solid-state amp?
Good question.
The first question is IF it is necessary for the loudspeaker to produce "less" absolute values of distortion than the amp for the contribution of the amplifier to be heard?
Then what is the relationship between the two?
Show me these papers?
Or, let's apply for some grants to do research?
Take the now less than full state-of-the-art SA8535 HF driver.
It was/is spec'd at 128dB @40watts (full power) and <1% THD at that level.
Assuming linear drop in distortion with level, work backwards to >30dB lower to an average SPL level. Compare to the typical HF driver?
Or compare to a top quality compression driver + horn...
Something to consider.
_-_-
The first question is IF it is necessary for the loudspeaker to produce "less" absolute values of distortion than the amp for the contribution of the amplifier to be heard?
Then what is the relationship between the two?
Show me these papers?
Or, let's apply for some grants to do research?
Take the now less than full state-of-the-art SA8535 HF driver.
It was/is spec'd at 128dB @40watts (full power) and <1% THD at that level.
Assuming linear drop in distortion with level, work backwards to >30dB lower to an average SPL level. Compare to the typical HF driver?
Or compare to a top quality compression driver + horn...
Something to consider.
_-_-
What does this challenging question have to do now ?
You have solid data to support this extraordinary claim or you don't. If you don't, what is the point of an "explanation" for something imaginary, other than the fun of telling stories? If you do, please give details.
You're aware that there's a significant cash prize available if you could distinguish that Crown against an "ordinary" amp by sound alone?
It is indeed. In published ears-only tests of amplifiers, listeners are readily able to pick out differences. Nothing remarkable about that. Humans are fantastically sensitive to level, frequency response, and clipping/recovery. They are sensitive to noise, compression, and some phase artifacts. That's been shown repeatedly in the papers you are encouraged to read. This may or may not be good for your commercial interests, but it is nonetheless what the data show.
No I have no such data and I don't know what one should measure if there is anything that could explain the slam. One would need to know what to look at first, I guess.
What would you measure? the/a loudspeaker system fed by the amp under test ? (e.g. impulse response with rise/decay time of the woofer's cone ?)
The amplifier ? e.g. amount of feedback on the various loops ? rise time ? output resistance / damping factor ? Some of these figures are already available from the datasheet of the manufacturer and they are sometimes abnormal (for instance damping factor 20,000, S/N ratio 120dB) see http://www.crownaudio.com/media/pdf/legacy/136734.pdf
Can we explain sound differences by the measures alone ? As far as I know, the jury is still out on this.
Since this is a DIY forum: I did add one decoupling 20uF MKP cap on each 6800 uF 'lytic in the PS. No big revolution of course, and it's been a while ago now, but if I rememver it did add a little smoothnes to the sound.
Yes, dear SY.
Your pejorative firing shots at some presumed "commercial interests" is quite frankly utter BS. Stick to the technical arguments.
Let's see your home system and its amplifiers. Shoot us the link.
Now what's ur trick here, because obviously there is one coming. You state:
Please tell me more about the cash prize for determining by ears the diff between a Crown and something else? Let's get specific... the conditions and rules count in something like this. Is this the Amazing Randi's prize? Or another...
Anyhow, since you can't hear the differences, you won't be listening to a Crown MacroTech any time soon, and you don't feel the need to design power amps, since you can buy a used Adcom or Bryston for a few hundred $$ and less if you do the repair urself??
Your pejorative firing shots at some presumed "commercial interests" is quite frankly utter BS. Stick to the technical arguments.
Let's see your home system and its amplifiers. Shoot us the link.
Now what's ur trick here, because obviously there is one coming. You state:
- but? There must be a "but".
Please tell me more about the cash prize for determining by ears the diff between a Crown and something else? Let's get specific... the conditions and rules count in something like this. Is this the Amazing Randi's prize? Or another...
Anyhow, since you can't hear the differences, you won't be listening to a Crown MacroTech any time soon, and you don't feel the need to design power amps, since you can buy a used Adcom or Bryston for a few hundred $$ and less if you do the repair urself??
First, determine if the claimed effect is real. Ears-only testing. If that comes up null, shrug and worry about something else. If you are able to hear it without peeking or other non-auditory cues, then you can start reasonably wondering about how to measure it. Trust your ears- and only your ears- when it comes to sound.
I'd put my money on the former outcome, but I'm certainly willing to be surprised.
Thanks for confirming that, bear. I have not bothered trying to access these "studies", because other work by the key authors that SY points to, that is publicly available, clearly shows their "bias" - and that their thinking is riddled with assumptions and lack of rigour ...
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