2.4KW amp, anyone?

[DonH50]

2.4 kW class A would pull more than 7 kW, quite a bit more than your average home outlet. Actually, probably more than your average home uses... The amps I have used that approached that ran on 240 V.

Afterburners, argh... Got to hear an engine test in my younger days whilst helping test radars. Engine mounted in a stand inside a big hanger covered with dirt and sandbags with a brick exhaust capture area behind. It hurt through the earmuffs, loud enough to make my skin hurt. Then they told me people aren't usually allowed in the hanger during the test, both due to sound and safety (followed by pix of the crater where the hanger was before being rebuilt after a failed test -- they only use a little fuel, but it's still a lot of energy). I can't imagine a rocket engine test, though I saw the test rig for one in FL (or AL, I forget).

 

[fas42]

From the start, it sounded like a thought experiment into a possible commercial product.

High crest factor is possible, but if you insist on doing it in class A topology, that kind of power level will require special mains hookups that only very few dedicated audiophiles will bother with. If you designed a class H amplifier, this would be possible and quite pedestrian on a 15A residential outlet..

And that's exactly what it is: Steve felt that it was more suited in the DIY forum, so here we are ...

Why are people not reading my posts? At the moment it's going to be some type, version or variation of class A/B, done intelligently so it doesn't smoke your power board more than it needs to. I don't have hangups about feedback, so this will be used correctly to make sure the device doesn't misbehave or go floppy at any point; it will have McIntosh levels of distortion at least at the average/rated power and hopefully also at peak power ...

Frank

 

[fas42]

By the way, to give a context to Basspig Mark's needs, if he's using 100dB sensitivity speakers as he mentioned earlier, then that 2.4KW peak translates to about 134dB at 1 metre, almost just enough to keep him happy ...

Frank

 

[Mark (Basspig) Weiss]

Ah yes, Redstone Arsenal. I remember the Saturn V rocket tests. Quite impressive.

One possible solution to the Class A/B power delivery is to use a transformer with a higher secondary voltage in the power supply, and allow it to sag under load. The rail voltage would be pretty high, so expensive capacitors come into play. And put about a farad's worth of capacitance in there, too. Very pricey caps. The transformer would be capable of delivering the kW or so continuously that would be needed for sustained 600W output, while being able to deliver 4X as much (stored in the capacitors) from an idle state to full signal. Ie., the short term peak power would be high as long as the capacitors' charge holds out.

There comes a point where if you're going to reproduce more than a solo violin or cello, you'll need to move up to higher sensitivity speakers, possibly in great numbers in arrays. Things like pyrotechnics require instantaneous high SPLs. But even a snare drum hit can be extremely loud, especially if close-miked and digitally mastered with no compressors or limiters. It's the high peak SPLs that keep the neighbors thinking I have a live band down here.

 

[fas42]

One possible solution to the Class A/B power delivery is to use a transformer with a higher secondary voltage in the power supply, and allow it to sag under load. The rail voltage would be pretty high, so expensive capacitors come into play. And put about a farad's worth of capacitance in there, too. Very pricey caps. The transformer would be capable of delivering the kW or so continuously that would be needed for sustained 600W output, while being able to deliver 4X as much (stored in the capacitors) from an idle state to full signal. Ie., the short term peak power would be high as long as the capacitors' charge holds out.

Yes, that's where the real action is going to need to be, in the power supply. And there are a number of ways of doing it, depending on how long you want to sustain the peak: the point as far as I'm concerned is for the amp to able to do it for the crest factor of "normal" music, rather than for some special effects track. The trouble about doing it just to cope with the latter is that the cost of the amp would go up dramatically, just to satisfy the urge to show off to visitors, and for those who have special "needs", like yourself.

if you're going to reproduce more than a solo violin or cello, you'll need to move up to higher sensitivity speakers, possibly in great numbers in arrays. Things like pyrotechnics require instantaneous high SPLs. But even a snare drum hit can be extremely loud, especially if close-miked and digitally mastered with no compressors or limiters.

Now I'm curious about your feeling that large peak SPL is required, even for some normal music. What do you feel is the maximum acoustic level that someone listening to live and PA amplified music of all possible types would experience when sitting in a reasonable, appropriate distance from the action? Here I'm obviously leaving out the brain dead teenagers who climb into PA bins ...

Frank

 

[Phelonious Ponk]

So maybe RMS has been a ruse all along. Maybe the thousands of amp and speaker companies that have used it as a standard knew all along that "average power" was more accurate. They still used it. It's still the standard. If I'm going to understand, even in broad terms, how powerful your amp's going to be and what kinds of speakers would be safe hook up to it, RMS is the touchpoint.

Why not do the math? Why nor use it so everyone who's not and EE can easily compare your amp to all the others out there?

Tim

 

[JackD201]

IIRC the use of RMS was a standard that was government mandated and it was the FTC at that. I don't know what the CE agenda was for choosing such a strange standard. Frank may be kooky, sorry Frank, but he is telling the truth when he asks "how many minutes". Again IIRC RMS is basically how long an amp can go before it burns out. The CE is preoccupied with safety and not quality after all. The standard seems to me an arbitrary one and is almost as useful as an appendix. At least the latter gets you a possible look at a pretty nurse if it blows up. All an amp will give you is some acrid smoke. What we do know is that amps that may have the same 100wpc RMS ratings often do not have the same voltage or current ratings. Dr. Geddes (Earl) is on record as saying as much about the usefulness of RMS and from my limited experience as a consumer, I agree with him.

So how's about it? Forget RMS. Let's go rated and peak voltage and current into 8,4,2 and 1 ohm loads. It's much easier to tell the limp from the hard, yes?

 

[Phelonious Ponk]

I'm willing to forget RMS. Can anyone help me, then, with some frame of reference that will help me place Franks spec in the food chain? I haven't a clue what kind of load 600 watts "average power" might drive. This seems to be an awfully good amp for the money. It might not be up to the task of the biggest, most difficult speakers out there, but it drives most quite well, without much fear of clipping...

Azur 840W Class XD™ power amplifier

Power Output: 200 Watts per channel into 8 Ohms
350 Watts per channel into 4 Ohms
500 Watts mono into 8 Ohms in bridged mode
800 Watts mono into 4 Ohms in bridged mode
Audio Inputs: 1 pairs gold plated RCA stereo phono inputs
1 pair XLR balanced inputs
Audio Outputs: 1 pairs gold plated RCA stereo phono outputs
1 pair XLR balanced outputs
Connections: 12v trigger in/out, control bus in/out, IR emitter in.
A & B speaker premium gold plated binding posts
Damping factor: >125 at 1 kHz
Frequency Response: 5Hz – 80kHz +/- 1dB
Signal to Noise Ratio: >90 dB (unweighed)
THD (unweighted): <0.001% 1kHz
<0.005% 20Hz - 20kHz
Power Consumption: Maximum 2400 Watts
Active (no signal) <180Watts
Standby <5 Watts

Dimensions (W x D x H): 430 x 365 x 148mm
Weight: 19.1kg/42.1 lbs

...can anyone tell me what it would be in "average watts?" Probably not. I don't see current or voltage.

Tim

 

[DonH50]

For all practical purposes, average W, "continuous power", and "W RMS" are equivalent in the audio world. By IHF/FTC rules, xxx W is defined as average power. Note that this is the average power delivered to a stated load with a single-tone input, it is not like an average of various signals over time, or like saying "it starts at 200 W then after 10 seconds has dropped to 100 W so the average power is 150 W"... Average power is the long-term (sustained) power rating. Manufacturers use RMS because it has the connotation of sustained long-term power and the public has come to accept that after being pummeled with terms like "instantaneous peak power" before the FTC stepped in and said to define power you must use RMS voltage and/or current.

In your example, I would assume all Power Output ratings are average power. That is the defined way to specify power ratings.

Note that since the power supply rails set the maximum voltage swing, for almost all audio amps P = Vrms^2/R and so if you halve R then power doubles. IF the design can sustain the current over time! Most cannot without getting too hot or for various other reasons, thus most amps do not "double down" as the load impedance drops.

Using the same equation, bridging doubles the voltage swing, so ideally a bridged design would deliver four times the power (double the voltage and square it to get power, a factor of 4 increase).

HTH - Don

 

[Phelonious Ponk]

Frank, I apologize for trying to hold you to what appears to be a rather vague standard. I even kind of knew that, as I understand that 40 watts from my old, high-current HK integrated seems to drive a difficult load with more ease than 100 watts from an inexpensive AV receiver. But it's the only standard I've seen used consistently enough to be sort of meaningful across many amps.

I understand that I was being a hard case, but here's the bottom line on that, no matter how much harder it may seem: You have repeatedly claimed to have achieved gravity-defying audio feats, given descriptions of performance that most would think unlikely if not impossible with the finest professional equipment, and you've claimed to have achieved it through minor or undisclosed tweaks to sub-midfi equipment. Fair or not, you're not a credible source at this point.

If you're going to publicly take on a big DIY project and expect to have any credibility, not just with me, but with anyone who has followed your posts here, you're going to need to be very transparent. Any deviation from standard specs/language/descriptions/methodology will need to be vigorously justified, otherwise we'll probably just assume you're faking it. That's hard, probably even harder than I've been up to this point, but I'm afraid it's the cold, hard truth.

Again, my apologies for latching on like a bulldog on your cuff and holding you to a standard that's not all that standardized. I followed your link. I'm not an EE. You might have to explain to me why "average power" is a good standard and how I can reference it to other amps that don't use that rating. And you'll probably have to talk real slow.

Tim

PS: Oh yeah...we're gonna need pictures, too.

 

[JackD201]

Yeah! Pictures!!!!!!!!!

 

[Phelonious Ponk]

See how easily amused we are, Frank? Entertain us!

Tim

 

[Gregadd]

I remember this http://www.angelfire.com/electronic/funwithtubes/Amp-FTC-Power.html

 

[DonH50]

I did not recall that. So, is that true, that the FTC dictated the term "RMS power"? Great. Next, look for a resurgence of laws to redefine pi as 3 since 3.141592654... is too hard for middle-schoolers to use in calculating the area of a circle.

Yeesh - Don

 

[Phelonious Ponk]

It reads like a litany of reasons why I was right not to trust "average power" and insist on the RMS standard. And it's encouraging that even though they haven't been required to since the 80s, most manufacturers still follow most of those rules and list ** RMS power, 20 to 20Khz, both channels driven, into *Ohms.

Enter the Federal Trade Commission.

With things so totally out of hand that nothing you read about amplifier power could be trusted the government stepped in. Some say this was good and others say it was bad. But good or bad, it was done.

NO MORE ADDING CHANNELS. The rules said that specifications had to be stated in watts per channel.

NO MORE PEAK POWER. Because the confusion about power was so pervasive the FTC felt compelled to make up something called RMS power. Meaning the RMS voltage across the load multiplied by the RMS current through the load. The stated specifications had to use the phrase "RMS power".

LOAD IMPEDANCE MUST BE STATED. The load impedance at which the power was measured had to be clearly stated along with the power. If the power was specified at 4 ohms, or even 2 ohms, it had to be stated and the specified load had to be used when the measurement was made.

NO MORE FIDDLING WITH THE POWER SUPPLY. The amplifier had to be tested in the same state it would be delivered to a customer. Everything had to be strictly stock, suping up the test version would no longer be allowed.
There were other tricks that were banned. For example the test model would most likely be removed from its cabinet and fans set up to blow a lot of air over the heat sinks. That would keep the poor little overworked transistors from overheating and burning out during the test. Sometimes they would even supplement the heat sinks to further increase the power output.

A very early trick was to test with only one channel driven. FTC rules said "We'll have no more of that. The test had to be made with both channels driven to the specified power.

The heat sinks had to be adequate to the task. Before the test, the amplifier had to be operated at 1/3 power, both channels, for 30 minutes. This is the highest dissipation condition for a class B amplifier. A hot amplifier delivers less power than a cold one so this rule ensured that the amplifier was tested under worst case conditions.

Frequency response had to be specified honestly as well. An amplifier that would deliver 60 watts at 1,000 hertz but 30 watts at 20,000 hertz could only be advertised as a 30 watt amplifier.

Tim

 

[fas42]

I understand that I was being a hard case, but here's the bottom line on that, no matter how much harder it may seem: You have repeatedly claimed to have achieved gravity-defying audio feats, given descriptions of performance that most would think unlikely if not impossible with the finest professional equipment, and you've claimed to have achieved it through minor or undisclosed tweaks to sub-midfi equipment. Fair or not, you're not a credible source at this point.

That's fine, Tim , we'll just move on. And I in turn will apologise to you and the others who have found it hard to accept or come to terms with some of the things I have stated or "claimed". In hindsight it was unfortunate that I was using the equipment that I've been referencing in my postings, the HTIAB as many like to call it, but it was purely a timing thing: a few years ago I was using totally audiophile creditable gear to do my fiddlings and investigations.

So let's just say this new project is my attempt to redress the situation,

And now a couple of related thoughts:

Tim, at one stage you asked about the Status Quo album I use for testing, the one that terry called "atrocious". Did you, or anyone else by chance, try this on on your or their own systems? The specific reason I mention it, as I just realised this morning, is that it has effectively been my version of Art Noxon's MATT test. If a system reproduces this album "correctly" then I don't need to worry about any other testing, I know I can put on any music whatsoever and it will sound good ...

And to create a reference about where I am coming from in amp power, and where I want to investigate going with this new one, I have the manual for the 2150B Perreaux here, and it still looks pretty impressive:

Rated power: 200W continous, both channels driven, into 8 ohms, 20 to 20,000Hz, less than 0.009% THD from 0.25W to rated power
Amplifier saturation (clipping): 700W into 8 ohms
Voltage swing: 164V peak to peak
Maximum current output: 10A per channel, fuse limited

The one area that's not so swish by modern standards is the current delivery, I would take the figure quoted as being RMS current. Now, in spite of the fact that it is quite a decent amp, I had no trouble hearing it start to compress with that Status Quo album, well over 20 years ago, and at very normal listening levels. The speakers were well regarded B&W bookshelf units, very straightforward crossover, they weren't the problem. That started me on the path on ramping up the capabilities of power supplies, and that made a huge difference to the Perreaux. Current output didn't change, neither was the amplifying circuitry altered, but the sound was capable of being far more dynamic, and real.

So this new unit is intended to be the next step in that progression, to ensure at all times that the power amp is not a limitation in the system ...

Frank

 

[Phelonious Ponk]

That's fine, Tim , we'll just move on. And I in turn will apologise to you and the others who have found it hard to accept or come to terms with some of the things I have stated or "claimed". In hindsight it was unfortunate that I was using the equipment that I've been referencing in my postings, the HTIAB as many like to call it, but it was purely a timing thing: a few years ago I was using totally audiophile creditable gear to do my fiddlings and investigations.

So let's just say this new project is my attempt to redress the situation,

That's not a situation that needs redressing, Frank. The Phillips was never really the issue, it was just an easy joke. If you had Steve's Lamms and Wilsons, reasonable, experienced audiophiles and audio pros could not attribute what you're reporting to anything less than a very active imagination. Sorry. I'm not trying to offend you, but that's just the plain truth.

Tim

 

[fas42]

That's not a situation that needs redressing, Frank. The Phillips was never really the issue, it was just an easy joke. If you had Steve's Lamms and Wilsons, reasonable, experienced audiophiles and audio pros could not attribute what you're reporting to anything less than a very active imagination. Sorry. I'm not trying to offend you, but that's just the plain truth.

Tim

OK, Tim, let's try and get to the bottom of things, yet again. Which "claim" do you find most difficult or offensive?

Frank

 

[Phelonious Ponk]

OK, Tim, let's try and get to the bottom of things, yet again. Which "claim" do you find most difficult or offensive?

Frank

It's an old road and we've run over it far too many times. Build your amp in peace. Don't forget the pictures.

Tim

 

[fas42]

I don't know about you blokes: you always want to see what's inside someone's gear ...

Frank