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[Ivan Beaver]

but are you talking about amps thermal cycling completely shutting off due to thermal overload... or just some kind of power sag (clipping? or fold-back limiting?).

I was talking about the power sagging.

And as you go lower, the sensitivity get lower on the speakers and also lower on our hearing.

So having "all you can" at the bottom makes a difference.

You can hear people say YEAH-and smile when you have a successfully deep "sweep".

On some system the sweep just "dies out" and doesn't have the same "finale" as other system.

At the end of the night do the kids care-I will leave that up for debate.

[John Roberts {JR}]

I was talking about the power sagging.

There are multiple short and longer term mechanisms that could affect LF power and power over time.

The quickest is the value amp cost saving corner cut that uses undersized reservoir caps that can not hold up the rail voltage for low frequencies below the mains frequency refresh rate. This is well known and easy to parse out by rated power differences between 20 Hz vs 1 kHz power.

Longer term as power transformers heat up, the winding resistance increases due to temperature coefficient of copper wire. This DCR increase causes PS voltage sag and lower power output (power varies with the square of voltage).

A clip limiter could drop the level a couple dB below this reservoir cap refresh rate but only if the amp was operating at the edge of clipping at mid band frequencies before. Transformer heating will cause a wide band drop in power.
 

And as you go lower, the sensitivity get lower on the speakers and also lower on our hearing.

So having "all you can" at the bottom makes a difference.

You can hear people say YEAH-and smile when you have a successfully deep "sweep".

On some system the sweep just "dies out" and doesn't have the same "finale" as other system.

Have you ever tried to start the sweep low frequency and sweep up for an amp that doesn't finish well? If an amp is being operated close to current limiting (<4 ohms) box impedance dips could trigger limiting. I can imagine modern smart amps that try to get clever about burst power delivery, since real music is not continuous level frequency sweeps but usually has at least a few dB of dynamic range.

At the end of the night do the kids care-I will leave that up for debate.

I think the operative question is do these amps audibly "sag" in use when playing music. I am repeating myself, but I suspect professional users with difficult applications have already figured out which cheap amps don't work for them, while they work just fine for the other 99%.

JR

PS: Note the higher power the amp, the less likely it will encounter or need continuous output power. I recall when amps first hit the 6KW power point and we wondered who could possibly use that? Since then amps have just gotten even larger.

[Ed Walters]

There is no simple answer-so wait till I get the paper finished and read it, and then ask further questions.

It's informative and entertaining to watch you and John debate, but, how about a simple answer to my original question:

1300 watts is which thing, the average power of a signal with a 6dB crest factor (thus requiring 5200 watt unclipped peaks) or the peak power of a signal with a 6dB crest factor (thus 1300 watts is the unclipped peak output)? or is it some other thing? How much power will it deliver for, for the sake of this argument, one second, before it self-limits one way or another? Or using any well-known standard test signal (IHF headroom comes to mind)?

What does 1300 watts mean relative to a speaker's average/continuous/rms power, "program" power, and peak power, ordinarily 3dB and 6dB higher? Without some kind of idea which end of this the 1300 watts means, appropriately matching it to a speaker's power handling capabilities is a crapshoot -- if it's 1300 peak then I put it with speakers rated at 650 program/325 sine, and if it's 5200 peak, then it's matched to speakers at 2600 program/1300 sine -- that's a 4:1 power ratio; given what the spec says, I want to know which end of that we are talking about. 

So what does the rating mean?

Ed Walters

[Tim McCulloch]

It's informative and entertaining to watch you and John debate, but, how about a simple answer to my original question:

1300 watts is which thing, the average power of a signal with a 6dB crest factor (thus requiring 5200 watt unclipped peaks) or the peak power of a signal with a 6dB crest factor (thus 1300 watts is the unclipped peak output)? or is it some other thing? How much power will it deliver for, for the sake of this argument, one second, before it self-limits one way or another? Or using any well-known standard test signal (IHF headroom comes to mind)?

What does 1300 watts mean relative to a speaker's average/continuous/rms power, "program" power, and peak power, ordinarily 3dB and 6dB higher? Without some kind of idea which end of this the 1300 watts means, appropriately matching it to a speaker's power handling capabilities is a crapshoot -- if it's 1300 peak then I put it with speakers rated at 650 program/325 sine, and if it's 5200 peak, then it's matched to speakers at 2600 program/1300 sine -- that's a 4:1 power ratio; given what the spec says, I want to know which end of that we are talking about. 

So what does the rating mean?

Ed Walters

Watts are not Volts, they have no crest factor independent of the output voltage of the amplifier.

[John Roberts {JR}]

Complicated isn't it?  Amps have short term peak and longer term average output  too,,,

Maybe a better question is which amp(s) do they recommend?

Many of the rule of thumb power ratios are just that vague approximations that seem to work over time.

JR

[Tim McCulloch]

I just saw these on Danley's web site. They look really really nice. Like I need to start a fund for them nice.

Are these units actually out yet? Any word on pricing and availability?

Ivan?

DNA 20K4 Pro Amplifier
http://www.danleysoundlabs.com/products/amps-dsp/dna-10k-20k-pro/


DNA SC48 DSP Processor
http://www.danleysoundlabs.com/products/amps-dsp/dna-sc48/

The DNASC48 looks rather "Ashly Audio-like".  Ashly builds good stuff and if DSL is having them OEM it should be RFG.  /acronyms

[Ed Walters]

Watts are not Volts, they have no crest factor independent of the output voltage of the amplifier.

No, Watts are not Volts. But crest factor is unitless; it is simply the ratio of peak to rms for any waveform. Thus when talking about an amplifier delivering a signal into a known and specified purely resistive load, that crest factor can be discussed in terms of power or voltage or current, all depending on whichever ratio of peak to rms you are measuring. Further, given that the amp is being tested with a specific resistive load, stating watts or volts or amps doesn't matter, they are essentially interchangeable (different numerical scales of course). We use whatever unit/measure is convenient and easily understood.

see wiki on crest factor here.

Ed Walters

[David Buckley]

The quickest is the value amp cost saving corner cut that uses undersized reservoir caps that can not hold up the rail voltage for low frequencies below the mains frequency refresh rate.

This is now regarded as a feature, and if one is simulating that 100W stack, then it has to have that mains modulation thing to sound authentic.  The old Ampulator even had a front panel pot for it.

[John Roberts {JR}]

This is now regarded as a feature, and if one is simulating that 100W stack, then it has to have that mains modulation thing to sound authentic.  The old Ampulator even had a front panel pot for it.

Wait for it... at some point in the future Danley will have to offer plug-ins so they can add distortion to make their speakers sound like other brand's. 

JR

[Scott Carneval]

Could you not just illustrate the duty cycle with a graph rather than a simple, yet very complicated, number?  Time on the X-axis and power on the Y-axis. And if you really wanted to give a number for simple comparison, do it the same way you rate the frequency response with -3 and -10 points. Such as a -10 and -50 points, rated in time (milliseconds, minutes, hours?) where the amp drops to 90% of its rated output and 50% of its rated output. Having two points would help to understand how quickly it drops off.  For the purpose of the test you would use a sine wave at 20hz. Or do multiple tests at 20, 30, 50, etc. similar to how polar plots are given at several relevant frequencies.


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