Do you want an amplifier to sound good, or one to charge a car battery.
What earthly use is 120 output amps? Where is it going to go? certainly not into an 8 ohm speaker -- unless it is driven by 960 volts and 115,200 watts
yeah 120A is extreme but what if a speaker dips to 3 or even 2.5ohms?
and are those ratings real?
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You have to read carefully! The mentioned currents are so-called peak values. These currents will only appear for some milliseconds (until the electrolytic capacitors in the power supply are discharged).
The currents for the class-D amps are specified as "continue" values!
John
i know that but i don`t think so.
my amps datasheet says current limit 28A (stop mode after limiting for 80ms)
unless peak and continue is the same for class d but then what`s the point?
Alot of marketing LIES, and stupid people believes.
To confirm that, take by example Powersoft amplifiers , wich have 15 Amperes fuses after rectification and storage capacitors.
How can it deliver 130 Amperes on output?
BIG lie, as the claimed 20000Watts from 12 Amperes breaker, at 120 volts, grace to thei WONDER PFC... Ha Ha ha.
To confirm that, take by example Powersoft amplifiers , wich have 15 Amperes fuses after rectification and storage capacitors.
How can it deliver 130 Amperes on output?
BIG lie, as the claimed 20000Watts from 12 Amperes breaker, at 120 volts, grace to thei WONDER PFC... Ha Ha ha.
Hi,
Because fuses react to average current, not very short term peak currents.
Peak amplifier currents are very short term into almost perfect shorts, and
are fairly meaningless, but a feature of how (long it takes) the protection
(to) kicks in, (if it has built in time constants).
It is near pointless number chasing, but not necessarily lies.
rgds, sreten.
Man, no search for contradiction, but music is not a very short peak signal, even if musical program is much lower on amplitude than a pure sinewave.
Consider that amp must deliver @ 0 db output power, a passage of music (dubstep or better reggae), with a constant 30-40-50Hz synthesizer or bass guitar, for couple seconds 3-5-8 seconds constantly.
What's happening with burst power, with burst output amperage, with all per ansamble?
Will drop alot, so power claimed is a BIG LIE.
Like here, where phisycal law are outdated:
Or here, real comportament of it, where shows big lies about power declared at specifications:
So, what do you have to tell after you saw that?
Pic here:
http://postimage.org/image/zbuh9nmoz/
Consider that amp must deliver @ 0 db output power, a passage of music (dubstep or better reggae), with a constant 30-40-50Hz synthesizer or bass guitar, for couple seconds 3-5-8 seconds constantly.
What's happening with burst power, with burst output amperage, with all per ansamble?
Will drop alot, so power claimed is a BIG LIE.
Like here, where phisycal law are outdated:
An externally hosted image should be here but it was not working when we last tested it.
Or here, real comportament of it, where shows big lies about power declared at specifications:
So, what do you have to tell after you saw that?
Pic here:
http://postimage.org/image/zbuh9nmoz/
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130A into short is virtually no power. Class D amplifier is a power converter, which ideally consumes the power proportionally to output power.
Most of the Members replying here do not seem to understand the difference between resistor loads and reactive loads.
An amplifier tries to reproduce a scaled copy of the input voltage at the output.
When the load sees that voltage it responds by demanding an output current.
That current, whether average, or peak, or short term transient peak, comes from the amplifier decoupling and the PSU.
When one tests an amplifier for maximum output power one specifies the resistor loads that the amplifier can drive and for how long.
A typical long term spec would be 200W into 8r0 @ 1kHz and less than 0.1% distortion.
To drive an 8r0 resistor to 200W, the amplifier must provide 40Vac and 5Aac.
That results in the Power (I*V) measurable at the resistor.
An Audio Power Amplifier is generally expected to drive a reactive speaker. Many of these speakers contain more than one driver and use a crossover to partition the frequency bands to suit the drivers in the speaker.
The combination of drivers and crossover components results in a load that behaves nothing like a resistor. That's where the problem comes.
How does the amp designer design for the tens of thousands of different speaker on the market that the user may choose to connect up?
The designer assumes his amplifier will be capable of driving a certain type of load and he will specify that conditional load. Let's say he specifies that the amplifier is capable of driving an 8ohms speaker and also capable of driving a 4ohms speaker.
Now let's return to numbers.
That same amp that was 200W into 8r0 may also be specified as being capable of driving 4ohms speaker.
The 4r0 specification line would state something similar to 370W into 4r0 @ 1kHz and less than 0.1% distortion.
That would be equivalent to 38.47Vac and 9.62Aac and is also equivalent to 54.4Vpk and 13.6Apk.
This is simply driving a non reactive resistor with a sinewave and already we are up to 13.6Apk from a pair of supply line that are @ ~+-45Vdc.
There is much reported research where the peak currents into actual speakers have been measured.
For fast stopping and fast stopping transients in real music signals the actual peak currents are reported @ upto 3 times to 5times what the resistor equivalent speaker would be expected to draw.
I'll only take peak transient current at the 3times the equivalent resistor current value.
For our 4ohms speaker the current is likely to peak out at not 13.6Apk but more like 40Apk on fast starting and fast stopping transients.
But this is not 40Apk into a short circuit. It is 40Apk into a reactive load.
In comparison, the short circuit peak current capability is far less onerous a test, than driving a real loudspeaker.
What if the supply rails were +-70Vdc or +-100Vdc? The peak transient currents will be proportionately higher if the amp is adjusted to use the extra power capability.
What if the user buys a low impedance capable amplifier because he wants to be able to drive a pair of 4ohms speakers wired in parallel.
These latter examples would require current capability well in excess of 100Apk.
An amplifier tries to reproduce a scaled copy of the input voltage at the output.
When the load sees that voltage it responds by demanding an output current.
That current, whether average, or peak, or short term transient peak, comes from the amplifier decoupling and the PSU.
When one tests an amplifier for maximum output power one specifies the resistor loads that the amplifier can drive and for how long.
A typical long term spec would be 200W into 8r0 @ 1kHz and less than 0.1% distortion.
To drive an 8r0 resistor to 200W, the amplifier must provide 40Vac and 5Aac.
That results in the Power (I*V) measurable at the resistor.
An Audio Power Amplifier is generally expected to drive a reactive speaker. Many of these speakers contain more than one driver and use a crossover to partition the frequency bands to suit the drivers in the speaker.
The combination of drivers and crossover components results in a load that behaves nothing like a resistor. That's where the problem comes.
How does the amp designer design for the tens of thousands of different speaker on the market that the user may choose to connect up?
The designer assumes his amplifier will be capable of driving a certain type of load and he will specify that conditional load. Let's say he specifies that the amplifier is capable of driving an 8ohms speaker and also capable of driving a 4ohms speaker.
Now let's return to numbers.
That same amp that was 200W into 8r0 may also be specified as being capable of driving 4ohms speaker.
The 4r0 specification line would state something similar to 370W into 4r0 @ 1kHz and less than 0.1% distortion.
That would be equivalent to 38.47Vac and 9.62Aac and is also equivalent to 54.4Vpk and 13.6Apk.
This is simply driving a non reactive resistor with a sinewave and already we are up to 13.6Apk from a pair of supply line that are @ ~+-45Vdc.
There is much reported research where the peak currents into actual speakers have been measured.
For fast stopping and fast stopping transients in real music signals the actual peak currents are reported @ upto 3 times to 5times what the resistor equivalent speaker would be expected to draw.
I'll only take peak transient current at the 3times the equivalent resistor current value.
For our 4ohms speaker the current is likely to peak out at not 13.6Apk but more like 40Apk on fast starting and fast stopping transients.
But this is not 40Apk into a short circuit. It is 40Apk into a reactive load.
In comparison, the short circuit peak current capability is far less onerous a test, than driving a real loudspeaker.
What if the supply rails were +-70Vdc or +-100Vdc? The peak transient currents will be proportionately higher if the amp is adjusted to use the extra power capability.
What if the user buys a low impedance capable amplifier because he wants to be able to drive a pair of 4ohms speakers wired in parallel.
These latter examples would require current capability well in excess of 100Apk.
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so assuming that class d amplifiers have lower current capability
than high end class ab amplifiers of the same power is correct?
Hi,
Simply not true. Power output into any purely reactive load is zero.
All heat generated by the output current must be dissapated by the
output devices. The purely reactive impedance limits this current.
Worst case is a dead short with peak currents and peak rail voltages.
This test illustrates how the protection works or blows up your amp.
Having said that, you can protect an amplifier against dead shorts,
but not stupidly low impedances that don't trigger the VI short
circuit protection, so the output devices will blow up.
The issue is how invasive any designed protection is with music,
the best allegedly sounding amplifiers have no protection at all.
Bad load or short, that means bye-bye to the output devices.
(SCP simply limits current to make sure the fuses blow first.)
SCP is less invasive than bad load protection, and probably
the best choice, all a moot point with well designed speakers,
where correctly connected the protection should never trigger.
But real speakers are not more onerous than a short, its all
about under what conditions protection kicks in, and why.
rgds, sreten.
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No, class D amps can often (if properly designed) deliver much higher currents into reactive and low-impedance loads, because they don't suffer massive power dissipation as a result. It's not difficult to design a class-D amp that can provide enough current to weld most voice-coils into a solid mass...
Unfortunately there are quite a lot of badly-designed class-D amps around.
(also, class AB amps...)
i am not talking about what can be done or 10000 watts lab gruppen.
i am talking about what`s already out there with 20-30A peak.
Ok, that will make you to think in other way about what you said.
Please, watch, all movies, entirely, with patience:
Here you can watch one made of me amplifier, AB class rated for around 700-750Watts permanent sustained, NOT BURST, on 4 ohms, working on real life use (4 ohm speaker).
Exclude from ecuation, perfect working of limmiter, based on input-output comparator and limmiting, it acts at more than 0.05% unmatched signal compairing input to output..
The Real Bass Test.mkv - YouTube
Ok, let's see same test with dummy load, also with same speaker parralel, but this time, both channels running at max power, with limmiter making his job very well, on CH2 (blue scope signal), ocasionally I disable limmiter:
Cu si fara Limmiter.mkv - YouTube
Ok, let's see same module amplifier, identically to the same one that I used on presented amp above, supplied at 2x99,5Vdc in idle, dropping till 2x96Vdc on max output on 2 ohms load , how it acts on dummy load, if you see any kind of limitations, asking from it to deliver his max out power on 4 and 2 ohms 1 volt under clipping prag!
Leco 4-2 ohm part 1.mkv - YouTube
Same test, but with just with ONE PAIR of outpud devices, at lower supply, around 2x85 VDC, (172Vdc total) but this time on speaker load:
See any kind of limmiting, excluding looses on wiring cables?
Part 4 - YouTube
Ok, now let's watch now,how it acts also a AB+B class amplifier, of bigger power, raded 2000Watts on 4 ohm, let's see if we see some kind of limmitations, when it gets his max power output:
2 Crown 4 Ohm 100 1000 10000 20000 Hz - YouTube
So, what you can say, burst amplifier can handle and act like those ones?
NO, they give a 40-100-500msecs FART burst of power, then limmiting to autoprotect, undersized output stages or power supplies...
So let's proove that I have mentioned,above,just mentioning this amp have undersized output stage, instead power supply (very strong one!) .
Watch here ,last movie for 2nite, same rating power amplifier, like above crown tested, same producer (crown), but total different acting (alot of limmitings on this second one):
It limmits itself, because not cappability of sustainde power, as showed on above pictures of comparation of LabG, Crown and Powersoft...
I-Tech 5000-7.MPG - YouTube
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