"Rise time, as long as it is high enough to accommodate 20 kHz at full amplitude, is not a measure of quality."
Need not even be that high - with several kW of 20kHz, every tweeter would be destroyed instantly. You NEVER have anything like full power at 20kHz other than an "accident" in your system.
Need not even be that high - with several kW of 20kHz, every tweeter would be destroyed instantly. You NEVER have anything like full power at 20kHz other than an "accident" in your system.
"I'm speaking about 2x6000Watts (2x5900 watts by specs) claimed by amplifier wich is K10 for 2 ohms load.
As you see, he is not able to sustain that power.
Other things is not so important.
Would you pay 5000 euros for that kind of amplifier wich on 2 ohms can sustain less than half power declared on oficial specs?
And those 2500 watts per channel delivered for couple seconds and after thermal limiting?"
Everybody above the age of around 15 should know how marketing works. Obvoiosly this is not the case and that may be the root cause to why the marketing guys are still in the business. Did you actually expect the product to SUSTAIN 2 x 6000W ? That is not possible even if the 45 Amp AC connector is fully loaded on 230V, let alone low line.
As you see, he is not able to sustain that power.
Other things is not so important.
Would you pay 5000 euros for that kind of amplifier wich on 2 ohms can sustain less than half power declared on oficial specs?
And those 2500 watts per channel delivered for couple seconds and after thermal limiting?"
Everybody above the age of around 15 should know how marketing works. Obvoiosly this is not the case and that may be the root cause to why the marketing guys are still in the business. Did you actually expect the product to SUSTAIN 2 x 6000W ? That is not possible even if the 45 Amp AC connector is fully loaded on 230V, let alone low line.
Crest 10001 is 5000w /ch @1 ohm ,done 2 decades ago. You can buy them now used for 1000 euro's ...
No disappointments .... 🙂
No disappointments .... 🙂
It's entirely possible to make a class D amplifier pass a square wave cleanly by running a very fast switching frequency, a fast feedback loop, and an output filter with a very high cutoff frequency. Only catch is such an amplifier would produce a ton of heat due to switching/gate-drive losses.
But it's pointless. What's a 10KHz square wave going to come from, a CD?
But it's pointless. What's a 10KHz square wave going to come from, a CD?
Man, for this amp, no matter what K10 or K3, in prospect are written power specs for 20Hz up to 20000Hz, audio band.
In music program, signals have much lower amplitude of high freqs compairing to mids or low freqs.
One good amp, must be able so sustain at 10Khz in squarewave (most power demanded regim signal for power amplifiers) his maximum power for minimum 10 seconds, as any kind of musical program, reggae, dubstep, techno, live band, etc, can be covered without limiting power or freq.
If you have looked at movies, those amps have poor rise and fall times, 23uSec at any oputput voltage starting at 3,5Vrms (where can be observable unfiltered carrier switching freq superimposed on the useful signal), until p-max.
So those bigger values of rise and fall times shown one slow amplifier.
One good amplifier wich will not denaturate sound quality of high freqs, especially above 10Khz must have a maximum rise and fall times of 6-8 microseconds from 10 to 90% of his swing output voltage.
Those type of amps are fast enough, in mine opinion.
To other colleagues:
I never said 20Khz at p-max on squarewave, don't put words in my hands.
And yes for one classD amp to be able to me fast enough to offer on output clean 10Khz squarewave, with good rise and fall times (5-8 uSec), the switching carrier freq must be much higher (1-1,5Mhz), to be able to use small value inductors on output (2-3 uHenries), than actually 400-500Khz used for 20uHenries...
I said that deja, the switching loses will be much higher, so officiency will decrease alot...
And yes, crest 10004 are one from the best "machine amplification", wich will ofer his maximum watts until last, wrotten in his prospect, without limiting power even on 2 ohms load.
I repaired couple of them, tested on dummy load, but no movies just pictures made, when opened first one.
http://postimg.org/image/90qxtp2j3/
http://postimg.org/image/clmtcx72n/
http://postimg.org/image/eepq18s9b/
http://postimg.org/image/icczqnf2n/
http://postimg.org/image/icczqnf2n/
http://postimg.org/image/lxdgnm8zz/
http://postimg.org/image/amasz924v/
http://postimg.org/image/ubt3bpa1b/
Great amps of real continuous power, despite weight.
Last edited:
A good amp must be able to sustain maximum power in the *audible* band. No need to reproduce a 10 kHz square wave (and please note that "kilohertz" is written as "kHz", not "Khz").
Several of us have pointed out that there is no need to reproduce a square wave (because any harmonics are beyond audible range anyway), but you seem to keep ignoring that, without offering any reason for being so focused on square waves.
You have not provided any reason for why those "rise and fall times" are required (and I don't understand the strange "from 10 to 90% swing" thing either - the usual specifications for amp "speed" are either slew rate, in V/s, or bandwidth).
We are clearly going around in circles - we keep pointing out the errors in your postings, and you just keep ignoring it and repeating, over and over again, your unsubstantiated claims of the importance of short rise and fall times and the ability to reproduce square waves.
Man, slew rate measurements of any amplifier must be made at 10000Hz on squarewave signal with dummy load, and rise-fall times values must be read starting from 10% to 90% of swing voltage Vpp value when amp is delivering 93-95% from his max power output (no clipping) on squarewave.
If you don't know that, learn it first, and after speak!
Slew rate measurements are essential for one quality amplifier,as that one must be.
Slew rate measurement shows us how fast or slow is one amplifier.
If that tested amplifier, will do honorable rise and fall times at 10Khz, certain his response in high freq audio band 8-20Khz will be immaculate.
End of story.
I please one admin to lock or delete this topic, It seems the poeple of here are interested only in contradiction, not technical problems.
Good bye.
If you don't know that, learn it first, and after speak!
Slew rate measurements are essential for one quality amplifier,as that one must be.
Slew rate measurement shows us how fast or slow is one amplifier.
If that tested amplifier, will do honorable rise and fall times at 10Khz, certain his response in high freq audio band 8-20Khz will be immaculate.
End of story.
I please one admin to lock or delete this topic, It seems the poeple of here are interested only in contradiction, not technical problems.
Good bye.
Last edited:
What's so special about 10 kHz? Where do your magic numbers come from?
Anyway, we all know how to measure them. That doesn't mean those measurements are relevant in any way.
So what were the slew rates of the amps you measured? So far you haven't presented any - all you have presented are rise and fall times (hint: as I wrote earlier, slew rate is measured in V/s - volt per second).
Anyway, all slew rate tells us is what the maximum frequency is that the amplifier can reproduce at full amplitude. As I keep repeating, as long as the slew rate is sufficient to reproduce a 20 kHz signal at full power, and the amplifier design is stable, the slew rate is sufficient.
I have nothing to talk with you as you don't even know why 10Khz are used as freq for slew rate measurements...
Frequency Response * : The amount of frequency versus amplitude distortion in an amplifier. A perfect amplifier will amplify all signals equally, regardless of frequency. Realistically, an amplifier needs a response of about 5Hz to 50kHz to ensure that all audible signals are catered for with minimal modification.
Output Power : This is most commonly measured into a resistive load. This is not done to improve the figures or disguise any possible shortcomings, but to ensure that measurements are accurate and repeatable. Power should only ever be quoted as "RMS", which although is not strictly correct, is accepted in the industry, and may be measured into 8 Ohms, or other impedances that the amplifier is capable of driving.
Output Current # : Not often measured, but sometimes quoted by manufacturers, this represents the maximum current the amplifier can supply into any load. It is rare that any amplifier will be called upon to deliver any current greater than about 3 to 5 times the maximum that the nominal speaker impedance would allow for the amplifier's supply voltage. Greater variations may be possible with some speaker designs, but (IMO) this represents a flaw in the design of the loudspeaker.
Power Bandwidth : This is usually taken as the maximum frequency at which the amplifier can produce 1/2 of its rated output power (this is the -3dB frequency). A 100W amplifier that can produce 50W at 50kHz will be deemed as having a 50kHz power bandwidth.
Slew Rate # : Closely related to power bandwidth, the slew rate is the maximum rate of change (measured in Volts per microsecond) of the amplifier output. The higher the amplifier power, the higher the slew rate must be to obtain the same power bandwidth.
So for those 5900 watts output power for 2 ohms as given in his specs we must have continuous around 108Vrms on 2 ohms, that means 54A rms, values that was not be obtainable for minimum 2-3 seconds.
I was not able to calculate slew rate, because the amp was NOT ABLE to sustain his maxmum power even for 2-3 secs, to have good callibration of oscilloscope.
Slew Rate - DiracDelta Science & Engineering Encyclopedia
Slew rate - Wikipedia, the free encyclopedia
http://s19.postimg.org/d6epo1imr/Untitled.jpg
http://www.audioholics.com/audio-amplifier/amplifier-slew-rate
Frequency Response * : The amount of frequency versus amplitude distortion in an amplifier. A perfect amplifier will amplify all signals equally, regardless of frequency. Realistically, an amplifier needs a response of about 5Hz to 50kHz to ensure that all audible signals are catered for with minimal modification.
Output Power : This is most commonly measured into a resistive load. This is not done to improve the figures or disguise any possible shortcomings, but to ensure that measurements are accurate and repeatable. Power should only ever be quoted as "RMS", which although is not strictly correct, is accepted in the industry, and may be measured into 8 Ohms, or other impedances that the amplifier is capable of driving.
Output Current # : Not often measured, but sometimes quoted by manufacturers, this represents the maximum current the amplifier can supply into any load. It is rare that any amplifier will be called upon to deliver any current greater than about 3 to 5 times the maximum that the nominal speaker impedance would allow for the amplifier's supply voltage. Greater variations may be possible with some speaker designs, but (IMO) this represents a flaw in the design of the loudspeaker.
Power Bandwidth : This is usually taken as the maximum frequency at which the amplifier can produce 1/2 of its rated output power (this is the -3dB frequency). A 100W amplifier that can produce 50W at 50kHz will be deemed as having a 50kHz power bandwidth.
Slew Rate # : Closely related to power bandwidth, the slew rate is the maximum rate of change (measured in Volts per microsecond) of the amplifier output. The higher the amplifier power, the higher the slew rate must be to obtain the same power bandwidth.
So for those 5900 watts output power for 2 ohms as given in his specs we must have continuous around 108Vrms on 2 ohms, that means 54A rms, values that was not be obtainable for minimum 2-3 seconds.
I was not able to calculate slew rate, because the amp was NOT ABLE to sustain his maxmum power even for 2-3 secs, to have good callibration of oscilloscope.
Slew Rate - DiracDelta Science & Engineering Encyclopedia
Slew rate - Wikipedia, the free encyclopedia
http://s19.postimg.org/d6epo1imr/Untitled.jpg
http://www.audioholics.com/audio-amplifier/amplifier-slew-rate
Last edited:
How about providing a reference to the relevant standard instead? As you surely know, there are many ways to measure slew rate, and it doesn't need to be done at a specific frequency, so I would like to know why you chose your particular standard.
You are clearly quoting some source. How about letting us know what your source is?
Exactly. So if you can't measure the slew rate directly, you can calculate it from the power bandwidth. Did you measure that?
I suggest you get an oscilloscope with a triggerable memory function. I don't think anyone manufactures scopes without a digital memory function these days...
P.S. It is not very helpful that you go back and edit your postings afterwards.
Just commenting on the links you added later - I suggest you actually read the pages you linked to. They show several practical ways to help you to measure the actual slew rate despite your oscilloscope calibration problems.
What to measure at that amp when output power fluctuates, not solid rock?
If I get sinusoidal signal he gives on output one short burst of power couple tenth of miliseconds and after it limits till 67Vrms on 2 ohms load (that's a little above 2000 watts, not 5900 watts as claimed), and in short time gets into thermal protection...
Search on google about quoting, do yourself researches, if you're so curious!
Crown makes those tests at 10Khz for squarewave signal, Yamaha too.
I think at least Crown engineerss deserve a little respect.
But maybe they are stupid and you're clever...
http://s19.postimg.org/nuigmvslv/Untitled.png
If I get sinusoidal signal he gives on output one short burst of power couple tenth of miliseconds and after it limits till 67Vrms on 2 ohms load (that's a little above 2000 watts, not 5900 watts as claimed), and in short time gets into thermal protection...
Search on google about quoting, do yourself researches, if you're so curious!
Crown makes those tests at 10Khz for squarewave signal, Yamaha too.
I think at least Crown engineerss deserve a little respect.
But maybe they are stupid and you're clever...
http://s19.postimg.org/nuigmvslv/Untitled.png
Last edited:
Of course I watched your movies and of course these numbers are not great at all.
On the other hand music reproduced through CD players won't do much better already before you get the signal to your mixer.
Don't panic - basically I am sharing your view that an amp should be faster than the expected signals. My point is more that you demand it to extreme, especially that you demand it with giant sloping, 10%-90%.
Music doesn't care a about definition which was intended to specify TTL circuits and switching devices.
It's just copy and paste that this definition is also being used for audio amps.
Nothing wrong with doing so. But as soon as the speed is comparable to the CD format, it is hard to directly translate the numbers into poor sound.
I do not dare to predict poor sound, neither just because also faster amps do exist, nor just because I prefer it faster for my own designs.
Also I share your view that power ratings which can be sustained only for short bursts have been invented mostly to trick customers and enable advertising with impressive numbers.
Coming back to the fundamental topic of your thread:
Your shown measurements are valueable and helpful to compare the amps in terms of power and speed.
It is great that one can have a look to your measurements and get an impression before shopping. And of course I am curious to see more.
So do you want to know the slew rate at maximum continuous power, or at peak power? If the former, you have to find out at what limit the thermal protection kicks in, and measure just below that point. If latter, just calculate the slew rate from the numbers above.
I have done my research, but no amount of googling helps me know what assumptions you are making.
Yes. It is a very common frequency, but in no way the only one.
So the only reason you use 10 kHz is that Crown and Yamaha use that frequency?
And please, "kHz", not "Khz".
Oh, and again - it is not very helpful that you go back and edit your postings.
Last edited:
Indeed. This is why I am curious about why DjLeco is claiming that it *has* to be measured that way.
Because slew rate tests must be done at almost maximum output level, to be able to calculate that slew rate because slew rate is dependant by output level, that's why must be calculate at higher power level , instead at 50%, or lower power.
As Crown engineers said here:
"insert a 10 Khz square wave and adjust amplitude to produce an output 10V below clipping"
So from here we understand slew rate tests must be made at couple procents under clipping level.
http://s15.postimg.org/kgu8avi57/Slew_rate.jpg
http://s13.postimg.org/beg02t8lj/image.jpg
Personally I trust Crown engineers, as after I have repaired and tested couple macrotech 5000 VZ amplifiers they respect or even exceed specifications.
Hope now all of you are clarified.
Look here an good slew rate of almost 72,5 volts per microsecond:
http://postimg.org/image/xz8sibhn3/
Last edited:
So your knowledge of slew rate measurement comes from a service manual?
Do you understand the relationship between power bandwidth and slew rate, and how to calculate the latter from the former?
Man, if even a service manual from ones of the most respectable amplifier producers, isn't relevant for you, leave me alone, I lost enough time to explain for you child's stuff.
Believe what you want, and that's it.
Go and enjoy your classD amp.
Have a good night.
Believe what you want, and that's it.
Go and enjoy your classD amp.
Have a good night.
Last edited:
- Status
- Not open for further replies.