Class D audio amp. - Page 1
Forum section: electronics / general

author: shakalnokturn
author_rank: Super Contributor
timestamp: July 13, 2025, 11:31:01 pm
content: Spotted this on the back label of a L'Acoustics LA12XCan anyone clarify the power figures ?It's a 4 channel amplifier, even if stated output was PMPO I don't see how it fits...

author: Analog Kid
author_rank: Super Contributor
timestamp: July 14, 2025, 12:06:15 am
content: That's what they claim:https://www.l-acoustics.com/products/la12x/Output power, all channels loaded:4 x 3300 W at 2.7 ohms4 x 2600 W at 4 ohms4 x 1400 W at 8 ohmsPlausible? I dunno.

author: shakalnokturn
author_rank: Super Contributor
timestamp: July 14, 2025, 12:11:34 am
content: I don't doubt that a class D amplifier capable of those figures is possible to build, It's the "Mains 1900W" versus >10kW total output power that I don't catch.

author: Analog Kid
author_rank: Super Contributor
timestamp: July 14, 2025, 12:14:27 am
content: Aaaaargh; missed that.Definitely does not compute.

author: themadhippy
author_rank: Super Contributor
timestamp: July 14, 2025, 12:27:23 am
content: sorry to the nay sayers,but L acoustics are a very reputable company (and made one of the best monitor wedges ever ,the 115fm ) and if they say it does it,it will.

author: Analog Kid
author_rank: Super Contributor
timestamp: July 14, 2025, 01:06:54 am
content: Quote from: themadhippy on July 14, 2025, 12:27:23 amOK, but how do you reconcile a stated max output of 13,200 watts (3,300 x 4) versus a stated input draw of only 1,900 watts?That just doesn't add up, does it?(Unless the input power is at idle, which doesn't make sense either)Over-unity?

author: themadhippy
author_rank: Super Contributor
timestamp: July 14, 2025, 01:23:15 am
content: clever psu design,lots of capacitors and the fact music aint a constant level

author: shakalnokturn
author_rank: Super Contributor
timestamp: July 14, 2025, 01:27:07 am
content: Quote from: Analog Kid on July 14, 2025, 01:06:54 amAt one point I was guessing our national Jean-Louis Naudin had been in the engineering team.

author: Analog Kid
author_rank: Super Contributor
timestamp: July 14, 2025, 01:29:30 am
content: Quote from: themadhippy on July 14, 2025, 01:23:15 amNo.

author: UnijunctionTransistor
author_rank: Frequent Contributor
timestamp: July 14, 2025, 02:33:14 am
content: No, it doesn’t compute.It may only be peak power capability, sustained for an extremely brief period.

author: Analog Kid
author_rank: Super Contributor
timestamp: July 14, 2025, 03:39:52 am
content: Ah yes, the games that are played with power ratings to bamboozle audio customers. Is itRMS power?Peak power?"Music power"?Some other power measure?

author: Haenk
author_rank: Super Contributor
timestamp: July 14, 2025, 04:59:24 am
content: For a glimpse into that technology, I advise to watch some of "Williston Audio Labs" videos, where he tests car amplifiers - which often come with insane power output stated.Surprisingly enough, even very cheap amplifiers easily deliver hundreds of Watts, the Kilowatt-range is not uncommon for somewhat more expensive models.The LA12X seems to retail for 10 KiloEURO. I assume a buyer would expect the promised power to be delivered.

author: Analog Kid
author_rank: Super Contributor
timestamp: July 14, 2025, 05:09:05 am
content: Quote from: Haenk on July 14, 2025, 04:59:24 amBut whatisthe promised power measured in? They don't say anything, just "watts".

author: Psi
author_rank: Super Contributor
timestamp: July 14, 2025, 05:13:56 am
content: Quote from: themadhippy on July 14, 2025, 12:27:23 amOne thing I noticed, the gap between / and 1 is larger than between z and /So perhaps a 1 has worn off and it's really 11900 W input.For 2600W output * 4 = 10400W that would be 87.4% efficient and around 80-90% is pretty normal for a class D.But I'm not totally convinced. It's just interesting that if you add a 1 in there everything makes sense.

author: Haenk
author_rank: Super Contributor
timestamp: July 14, 2025, 05:36:49 am
content: Quote from: Analog Kid on July 14, 2025, 05:09:05 amFrom the spec sheet:"Output power CEA-2006 / 490A (1% THD, 1 kHz, all channels driven) 3300 W" (that is at 2.7 Ohm; 2600W at 4 Ohm, 1400W at 8 Ohm)

author: Haenk
author_rank: Super Contributor
timestamp: July 14, 2025, 05:39:18 am
content: https://www.l-audio.com/cdn/shop/files/12_3.jpgThe inside looks quite beefy.

author: Haenk
author_rank: Super Contributor
timestamp: July 14, 2025, 05:49:44 am
content: Quote from: Psi on July 14, 2025, 05:13:56 amNot sure of the measuring procedure, but I would assume there is just not full load all the time, so with the stated power figures, this seems to be an average of about 10% load. Makes sense, as you usually don't play pure sine waves for a prolonged period of time but a very dynamic load.

author: paul cotter
author_rank: Regular Contributor
timestamp: July 14, 2025, 09:20:32 am
content: Possible, but you would need a one inch thick power cord all the way out to the distribution board. For 1900W input no way could it come near those figures with continuous sine on all channels. Peak power with very low duty cycle.

author: Zero999
author_rank: Super Contributor
timestamp: July 14, 2025, 09:41:45 am
content: What's new? Manufactures have being lying about the power output of their audio amplifiers for many decades.

author: shakalnokturn
author_rank: Super Contributor
timestamp: July 14, 2025, 10:28:07 am
content: Quote from: Zero999 on July 14, 2025, 09:41:45 amNo lies as long as the measurement methids of stated power are not specified.How many have been lying about power consuption ?

author: shakalnokturn
author_rank: Super Contributor
timestamp: July 14, 2025, 10:43:05 am
content: Quote from: Psi on July 14, 2025, 05:13:56 amI searched for other photos and found the same labelling in other places.There was also attached version which would make more sense if it were for power comsumption per channel.

author: Psi
author_rank: Super Contributor
timestamp: July 14, 2025, 11:02:27 am
content: As others have said, probably just saying it has the stored energy to temporarily drive 2600W speakers for typical music needs. (bass)And it needs up to 1900W continuous input power to do that.

author: Zero999
author_rank: Super Contributor
timestamp: July 14, 2025, 11:19:28 am
content: Quote from: shakalnokturn on July 14, 2025, 10:28:07 amThat's just an excuse. Just looking at the design of many amplifiers proves the power specification is fabrication. For example, I've seen an amplfier with a 12V power supply claimed to output 200W, which is never, ever going to happen, even if we assume peak power for all four channels into 4 ohm loads.

author: madires
author_rank: Super Contributor
timestamp: July 14, 2025, 12:09:16 pm
content: From Wikipedia (https://en.wikipedia.org/wiki/Audio_power#PMPO):QuoteI think that sums it up quite nicely. Reminds me of cheap PC speakers with a 2 * 3W amp chip stating something like 40W PMPO per channel.As a student I was lucky to work a while for a local high-end audio manufacturer. They tought me how to measure the performance of audio amps.

author: paul cotter
author_rank: Regular Contributor
timestamp: July 14, 2025, 02:22:45 pm
content: 2.7 ohms is an unusual figure for the heaviest load. Normally power is quoted for 8, 4 and 2ohms(if the amp can handle it, not all can). My guess is that a 2 ohm load would cause problems. One particular amp I was familiar with was a Carver model(pm 1200??) that was stunningly loud with excellent quality but was only capable of a couple of hundred watts continuous sine duty. This amp used a mains transformer that you could easily fit in your pocket and the whole thing was quite light in comparison with amps with equivalent music performance. The output consisted of a "stacked push-pull" output with three rails of around +-40v, +- 60v and +- 115v with diode commutation from one rail to the next, depending on signal level. There is a term for this output topology but this was 40years ago and I have long forgotten it.

author: SteveThackery
author_rank: Super Contributor
timestamp: July 14, 2025, 02:26:21 pm
content: Quote from: Haenk on July 14, 2025, 05:36:49 amCEA-2006 / 490A describes how the testing is done, and it definitely isn't any kind of dodgy "peak power for a millisecond into half an ohm" nonsense.Multi-kilowatt class D amplifiers are common in large music venues or PA systems, and it's not unusual to find racks of them. The only puzzle for me is that mains input power rating. The amps we had at Derby Uni required a higher power connection than the standard 240V 13A sockets used in the UK. This only serves to make me even more puzzled by that input power rating.

author: SteveThackery
author_rank: Super Contributor
timestamp: July 14, 2025, 02:28:01 pm
content: Quote from: shakalnokturn on July 14, 2025, 10:28:07 amAgreed. But the spec sheet under discussion does specify the measurement method: CEA-2006 / 490A.

author: themadhippy
author_rank: Super Contributor
timestamp: July 14, 2025, 03:51:59 pm
content: QuoteThats part of the magic spell,music aint a continues sine waveQuoteshoulda ask simon how its done.QuoteThe lab gruppen equivalantish fp10000, 4x 2.5kw into 2 ohms, requires a 16A input. 4 off em(2 foh and 2 on monitors) manage to get bloody loud before they pop a 6A breaker at rather loud volumes,and we'd regularly run that amp rack along with the rest of the sound kit and back line off a 16A supply without any problems,well apart from exceeding the venues noise limit.

author: temperance
author_rank: Super Contributor
timestamp: July 14, 2025, 05:03:19 pm
content: QuoteThat's because of the peak to average ratio of music. Plug in a function generator and the fuse will pop if nothing else in the amp starts to limit the input signal.

author: Analog Kid
author_rank: Super Contributor
timestamp: July 14, 2025, 06:16:45 pm
content: Personally, I wouldn't believeanyof those stated output power ratings--no matter how reputable that manufacturer may be--unless they state whether those watts areRMSinstantaneous peak power"music power"or some other kind of powerSeems like a major omission on their part. Unless their customers are all dummies who only care about marketing claims, which I'd find hard to believe.

author: Zero999
author_rank: Super Contributor
timestamp: July 14, 2025, 06:17:53 pm
content: Quote from: SteveThackery on July 14, 2025, 02:28:01 pmThat doesn't mean they're not lying. I always expect audio amplifier manufacturers to exaggerate the power output, until proven otherwise.Quote from: temperance on July 14, 2025, 05:03:19 pmMore often than not, the total peak power is given for all of the outputs added together. That's assuming it's not a complete fabrication of course, as it often the case.In your case the 2.5kW amplifier is specified per channel. I'm going to assume it's not a complete lie.A sine wave has a crest factor of1/√2and the peak power is double the RMS power.According to Google AI, the crest factor of music is between 10 and 20dB or 4 and 10, assuming for the sake of getting the highest peak power as possible, I'll use the higher end of the range. Power goes up by the square of voltage, so if the RMS power is 1W and the crest factor is 10, the peak power is equal to the RMS power multiplied the peak power squared, so 1*102= 100W.In your case, that 2.5kW per channel becomes 250W per channel, which is much more plausible.

author: Ziscool
author_rank: Newbie
timestamp: July 14, 2025, 09:28:34 pm
content: At least as I've understood Audio power amplifiers they are built with the intent to be able to play music and not test tones.because of this they are typically built to output about 1/8th of their stated power continuously. so this amplifier seems to be stating their power numbers in a similar way. since the 2600Wx4 = 10.4 kW, 10.4 kW / .125 = 1300Wthere is a AES standard that explains the discrepancy well but usually it comes down to real world music containing few peaks and most of the signal lies around this 1/8th level but you still need headroom to be able to play full scale for the few samples that actually exist in that region.

author: langwadt
author_rank: Super Contributor
timestamp: July 14, 2025, 09:58:22 pm
content: Quote from: Zero999 on July 14, 2025, 06:17:53 pmand assuming that crest factor you couldn't tell the difference

author: TimFox
author_rank: Super Contributor
timestamp: July 14, 2025, 10:29:25 pm
content: Quote from: Analog Kid on July 14, 2025, 06:16:45 pmAs I keep pointing out, "RMS watts" is a misnomer.You can do the math and evaluate the RMS value for the power dissipated by a sinusoidal voltage in a resistor, but it is not useful and is higher than the "mean power" for that voltage and resistance.Remember that RMS means "root-mean-square", the square root of the mean of the square of the voltage over time. The mean squared voltage divided by the resistance is the mean power.Unfortunately, when the hi-fi industry was fraudulently deriving inventive measures for amplifier power (including the infamous "+/- 1 dB" which meant "-1 dB"), the ignorant regulators specified RMS as a measure.

author: SteveThackery
author_rank: Super Contributor
timestamp: July 14, 2025, 10:36:07 pm
content: Quote from: Analog Kid on July 14, 2025, 06:16:45 pmBut they have: CEA-2006 / 490A.

author: Analog Kid
author_rank: Super Contributor
timestamp: July 14, 2025, 10:39:16 pm
content: Quote from: SteveThackery on July 14, 2025, 10:36:07 pmSo what flavor of power measurement is that?

author: themadhippy
author_rank: Super Contributor
timestamp: July 15, 2025, 12:05:53 am
content: Regardless how they measure it ,if it couldn't do what it said on the tin the speakers being powered by the amps wouldn't be giving the spl some clever chap has calculated they should be producing .Theirs plenty of l acoustic stuff being used worldwide,and has been for the last 30-40 years,for many major artist that any short fall would soon show up.

author: thm_w
author_rank: Super Contributor
timestamp: July 15, 2025, 12:37:35 am
content: Quote from: Analog Kid on July 14, 2025, 10:39:16 pmYou can google search and find that its a peak power test.Quotehttps://www.audiosciencereview.com/forum/index.php?threads/amplifier-peak-power-class-d-vs-class-a-b.19559/You can also read this TI document:https://www.ti.com/lit/an/slea047a/slea047a.pdf?ts=1752478022375"Instantaneous peak power" might be ~6x of RMS power.So in case of LA12X, 1900W input * 90% efficiency * 6 = 10kW. Which matches their output rating.

author: Analog Kid
author_rank: Super Contributor
timestamp: July 15, 2025, 12:40:22 am
content: Quote from: thm_w on July 15, 2025, 12:37:35 amGoddamnit; I know fucking well I can do a Google search.The reason I ask here is becauseI don't want to do a Google search.I'm asking people here who would know.Hey, maybe we should all just quit using this forum altogether.After all, we can find any answer we want by "Googling" it, right?Would that make you happy?Sheesh.

author: Analog Kid
author_rank: Super Contributor
timestamp: July 15, 2025, 12:48:06 am
content: Quote from: thm_w on July 15, 2025, 12:37:35 amWait; either I'm really missing something here, or something really doesn't add up.1900 watts is the rated input power, right?That means a single input of that many watts to the power supply.How can you multiply it by 6 (# of channels, which is actually 4, but whatever)? There's only one power input spread amongnchannels, so by your reckoning, we should have atotalpower output of 1900 * 0.9 which is 1710 watts.Total output power cannot exceed total input power.Each channel would be capable of producing 1710/4 or 427 watts.Am I wrong here?

author: temperance
author_rank: Super Contributor
timestamp: July 15, 2025, 01:17:35 am
content: QuoteAnalog Kid at it again. Lazy cunt.

author: thm_w
author_rank: Super Contributor
timestamp: July 15, 2025, 01:19:12 am
content: Quote from: Analog Kid on July 15, 2025, 12:40:22 amChill, I didn't know and it took me 20s to google and find out in the first few results.Quote from: Analog Kid on July 15, 2025, 12:48:06 amRead the TI document, which explains peak and instantaneous peak power how to measure it.QuoteQuoteIts no different from a high power RF pulse, a pulsed laser, etc. peak power can be enormous if the duty cycle is only 0.0001%.In this case its a short 1kHz burst of only 20 cycles. I believe that is a 2% duty cycle.

author: Analog Kid
author_rank: Super Contributor
timestamp: July 15, 2025, 01:58:55 am
content: Quote from: temperance on July 15, 2025, 01:17:35 amWell, fuck you too.And the horse you rode in on.

author: Analog Kid
author_rank: Super Contributor
timestamp: July 15, 2025, 02:02:32 am
content: Quote from: thm_w on July 15, 2025, 01:19:12 amNo; I'm talking about your multiplication of the input power (derated for amplifier efficiency) by 6.I don't understand that part; why did you do that?Remember, you wroteQuote

author: temperance
author_rank: Super Contributor
timestamp: July 15, 2025, 02:58:19 am
content: QuoteThis has been discussed. Read and try at least to do your best to understand what people wrote.

author: Analog Kid
author_rank: Super Contributor
timestamp: July 15, 2025, 03:42:25 am
content: Quote from: thm_w on July 15, 2025, 12:37:35 amSo that would be because ... there's enough capacitance in the amp to momentarily supply a "jolt" of power which exceeds the input power?

author: Haenk
author_rank: Super Contributor
timestamp: July 15, 2025, 05:24:04 am
content: Quote from: Analog Kid on July 15, 2025, 12:40:22 amEasy.Just cough up the money, if you want to read the details of the test procedure.People who do know would probably say "it's a complex procedure, you need to follow - with all kind of parameters being set and results measured". That's what test standards are for. Producing comparable results. Which *you* (and *I*) can not interpret, unless we purchase the test procedure specs document.On the plus side, we can still compare devices, by looking at the result numbers.

author: Analog Kid
author_rank: Super Contributor
timestamp: July 15, 2025, 05:41:42 am
content: Quote from: Haenk on July 15, 2025, 05:24:04 amAt the risk of belaboring the point, this whole brouhaha came about when Steve Thackery posted in response to my question about what kind of power measurement was used:QuoteTo which I replied:QuoteSo you're telling us that this (CEA-2006/490A) is some kind of Top Sekrit protocol that you have to pay money to see?Really?That's all; I'm just curious about how the power is measured, which somehow started this whole shit-storm ...

author: Haenk
author_rank: Super Contributor
timestamp: July 15, 2025, 06:23:19 am
content: Quote from: Analog Kid on July 15, 2025, 05:41:42 amActually, this is common for all industry standards - they often charge an arm and a leg for these documents. (Which is probably even reasonable, considering how much work is going into these. But annoying, if you are not an industry giant and have to pay with your own money...)

author: bsdphk
author_rank: Regular Contributor
timestamp: July 15, 2025, 06:25:29 am
content: On their homepage is a document titled "LA12X Architect Specification" and it says, as nearly the first thing:Amplification:• Output power (no limiter 200 ms sine bursts,1 kHz, < 1% THD, all channels):◦ 4 x 3300 W at 2.7 ohms◦ 4 x 2600 W at 4 ohms◦ 4 x 1400 W at 8 ohms• Amplification class: High-efficiency Class D• Maximum output voltage: 157 V (peak voltage)

author: racemaniac
author_rank: Contributor
timestamp: July 15, 2025, 08:26:49 am
content: It's documented in their owners manual:https://prdstglaxxwe001.blob.core.windows.net/webapp-lacoustics/documentation/ELECTRONICS/LA12X/EN/Owner's%20Manual/LA12X_OM_EN.pdf"An eighth (1/8) of the maximum output power corresponds to a loud music program with a small dynamic rangeand 9 dB of headroom (IEC standard power rating)."So the 1900W mentioned on the back is assuming 1/8th of the power actually used, and is an assumed real world worst case scenario.But that same page documents the amp can easily draw 5+kW in other situations (and theoretically could draw 10+kW if you indeed push every channel to full power via some synthetic benchmark)

author: paul cotter
author_rank: Regular Contributor
timestamp: July 15, 2025, 09:43:20 am
content: 200msec bursts. That explains it, a short burst of power before the psu buckles under a massive overload. Misleading IMHO, the only rating that would interest me is continuous sine.

author: langwadt
author_rank: Super Contributor
timestamp: July 15, 2025, 10:15:20 am
content: Quote from: paul cotter on July 15, 2025, 09:43:20 ambut a continuous sine isn't very relevant for music

author: SteveThackery
author_rank: Super Contributor
timestamp: July 15, 2025, 10:29:04 am
content: Quote from: paul cotter on July 15, 2025, 09:43:20 amI would be interested in both. The obvious problem with the continuous sine measurement is that nobody listens to a continuous sine. So although there is a kind of purity and simplicity about the continuous sine measurement, it's really only of interest in a laboratory.The purpose of CEA-2006 / 490A, and the other less formal ones, is that they are an attempt to measure and specify something closer to real life capabilities.Two amplifiers might have the same continuous sine rating (say 100W), but if one will deliver 1kW in short bursts and the other is hard-limited at 100W, then the first one will deliver a much more dynamic performance when driven hard with dynamic material like music.There are parallels everywhere. An engine with a large flywheel will temporarily deliver torque peaks well over the continuous torque rating. The energy storage system in F1 cars allows for brief bursts of acceleration in excess of that available continuously.

author: iMo
author_rank: Super Contributor
timestamp: July 15, 2025, 10:53:33 am
content: Quote from: bsdphk on July 15, 2025, 06:25:29 amWith "peak voltage max 157V" you may get up to 4.4kW on 2R7 in "average" during those 200ms..

author: Zero999
author_rank: Super Contributor
timestamp: July 15, 2025, 11:00:22 am
content: Quote from: langwadt on July 15, 2025, 10:15:20 amThat's true. I expect it depends on the music, or more how it's mixed and processed. If it's minimally processed then it'll have a large dynamic range and higher crest factor, making the peak music power an order of magnitude higher than the RMS power. If it's very processed "loud" music, then it'll have a smaller dynamic range and the peak power will not be as high compared to the RMS power. A recording of a live band, or orchestra, with no additional processing, will have a much greater dynamic range, compared to a procesed pop music track, downloaded from am app or website.

author: temperance
author_rank: Super Contributor
timestamp: July 15, 2025, 11:15:43 am
content: QuoteLong ago, amplifiers were heavy and could output the specified power continuously. Today, professional amplifiers contain limiters following the standard mentioned. Loudspeakers are rated the same way. They can't handle a continuous sine wave either. Because of physical requirements, it is not possible to provide enough cooling for the voice coil and magnet. Loudspeakers are maybe 0.5...4 % efficient. Imagine dissipating a 950 W in the mechanics of a loudspeaker 1000 W speaker. The voice coil of a typical PA loudspeaker is only 50...150 grams. Not a lot of energy is required to raise the voice coil temperature to its limits (the limiting factors are the wire insulation material and the glue used to assemble the voice coil and cone. Old loudspeakers couldn't handle a lot of power because they simply didn't have glue and voice coil formers capable of withstanding such high temperatures.) PA loudspeakers feature vents in their magnets such that air is being pumped around to cool down the voice coil. Enlarging the voice coil surface area doesn't help either because the air gap in the magnet must be made as small possible in order to achieve maximum efficiency. I've seen 15" and 18" loudspeakers where the cone and voice coil caught fire with the wrong limiter settings. The amplifier is not the limiting factor.It doesn't make sense for an audio amplifier to be able to output a continuous sine wave at maximum power either because music does not contain such signals, not even in very heavy compressed pop music. (Search for "loudness war") A 100 W amplifier can be powered from a 35 VA transformer and the transformer will be barely warm when playing music close to the clipping point of the amplifier for days.

author: paul cotter
author_rank: Regular Contributor
timestamp: July 15, 2025, 11:56:33 am
content: That peak output voltage of 157volts would need to be specified as the output voltage at 8, 4, 2.7 ohms or open circuit before a calculation of peak power. I fully get the argument about headroom above the continuous sine capability and this is fine for processed music but may lead to trips in live music where a sustained note could easily demand an impossible output. The carver amp that I mentioned was found to be unsuitable for bass duties in public address use but fine for the mid/high.

author: temperance
author_rank: Super Contributor
timestamp: July 15, 2025, 12:09:22 pm
content: QuoteWith the listener's ears bleeding.

author: TimFox
author_rank: Super Contributor
timestamp: July 15, 2025, 02:24:48 pm
content: This discussion can be compared with the normal use of “PEP”, peak envelope power (q.v.), to characterize linear amplifiers for SSB RF transmission.

author: racemaniac
author_rank: Contributor
timestamp: July 15, 2025, 02:50:36 pm
content: The manual mentions the 1900W rating is based on IEC standards, and a quick googling would indicate that IEC 60268-3 is applicable for amplifiers.But not sure if it's clear for most here yet: the 1900W rating isn't the actual max the amplifier can draw. It's just some rating based on the IEC standard, but it can go way beyond that (which i find strange, i'd expect the 1900W to mean "it won't go beyond this", not "in typical use it shouldn't go beyond this". But it's the standard it seems, you learn something every day).

author: paul cotter
author_rank: Regular Contributor
timestamp: July 15, 2025, 04:07:33 pm
content: When repairing amps I would always soak test them with a sine wave just short of clipping into a 4 ohm resistor bank for about 30mins.

author: SteveThackery
author_rank: Super Contributor
timestamp: July 15, 2025, 05:35:18 pm
content: Quote from: paul cotter on July 15, 2025, 04:07:33 pmI think that's an excellent idea.

author: temperance
author_rank: Super Contributor
timestamp: July 15, 2025, 05:56:10 pm
content: Quote from: SteveThackery on July 15, 2025, 05:35:18 pmFor "modern" amplifiers following the standards mentioned earlier, you can't use a sine wave for 30 mins because limiters in the amp will reduce output power after 8...15 seconds. We tested those with white noise close to clipping for an hour.

author: paul cotter
author_rank: Regular Contributor
timestamp: July 16, 2025, 08:23:13 am
content: It's around 10years since I did any amp repairs and at that stage most of what I was doing was on older models. The last one I did, a RAM(Spanish make) 4 channel and it nearly caused me to lose my marbles and the time spent was probably greater than the value of the amp- I was doing it for a friend. The problem was caused by an almost invisible crack in a surface mount resistor which intermittantly caused the current in one channel to max out, taking the output devices + the switch mode psu despite o/c protection. Complete rebuild and bang again! Complicating matters someone had been at it already with a lot of print repairs necessary due to poor soldering. Aaaagh!!

author: CaptDon
author_rank: Super Contributor
timestamp: August 23, 2025, 01:58:11 am
content: Paul, If you are referencing the Carver PM-2.0T, PM1250 or Clair Brothers version CBA-1000 they can do a combined total of 1000 watts all day long at 4 ohms for the monoblocs or 2 channels each around 500 watts at 4 ohms when talking about the 2 channel versions. There is an oddball, the CBA-1000M which has a built in crossover to biamp power the Clair monitor wedges. Carver claimed something like 625 watts per channel at 4 ohms both channels driven. That is a bit boastful but they will do 500 watts per channel at 4 ohms both channels driven. Clair Brothers units had some power supply tweaking and would indeed do 1000 watts sinewave all day long. The power supply switches at 1KHz and usually a bit of audible whine shows up in the speakers. I seldom see a PM-2.0T with damage to the audio section. The power switching transistors in the power supply module are the weak point and prone to fail when the amp is pushed to hard or running on really crappy 'Carnival Generator' mains power.

author: BrianHG
author_rank: Super Contributor
timestamp: August 23, 2025, 07:21:17 am
content: Quote from: langwadt on July 15, 2025, 10:15:20 amMaybe not, but, I can play some music with long bass notes, or classical music with some huge timpany drums segments which would destroy any amp with such phony specs.Quote from: temperance on July 15, 2025, 05:56:10 pmBut, you are all actually wrong, such trash would die or burn out during Sprach Zarathustra (it's basically a growing 20hz-25hz rumbling note going up to full volume going on for 2 whole minutes, with peak volume held for over 30 full seconds continuous at the end, and yes, it IS real music...) or during the cannon fire in 1812 Overture, Op. 49 with frequencies down below 5hz. (yes, this is music too...)Do you need more music examples. If it cant handle real music, I'd say it is garbage.What about non music examples like movies? I can find films like the first Fantastic 4 where the entire 2 minute intro through space is a growing rumble which lasts more than 30 seconds, or scenes in any movie where an earthquake is happening where the full volume rumble goes on for over a full minute or more.

author: SteveThackery
author_rank: Super Contributor
timestamp: August 23, 2025, 09:18:18 am
content: Quote from: BrianHG on August 23, 2025, 07:21:17 amI don't think I understand your point. Any amplifier will cope with such material provided you turn the volume down sufficiently to avoid overloading the output stage. All amplifiers have limitations - the only issue is how well those limitations are communicated to the user via the labelling.

author: Zero999
author_rank: Super Contributor
timestamp: August 23, 2025, 11:33:31 am
content: Quote from: temperance on July 15, 2025, 05:56:10 pmI believe pink noise, bandwidth limited to 20Hz to 20kHz, is normally used to test audio amplifiers, because its power spectrum is closer to real music, than white noise.

author: Coordonnée_chromatique
author_rank: Frequent Contributor
timestamp: August 23, 2025, 01:01:14 pm
content: Quote from: temperance on July 15, 2025, 11:15:43 amI've done it with a long throw subwoofer, a Block VCM36 and a TPA3118, the transformer was over 60°C in few minutes.

author: BrianHG
author_rank: Super Contributor
timestamp: August 23, 2025, 02:05:48 pm
content: Quote from: SteveThackery on August 23, 2025, 09:18:18 amI don't think you understand...I bought a 250w RMS / channel amp, I feed it full volume 1v RMS at the inputs and it will output the specified 250w / channel even with the classical music I listed all day long, no issues, not clipping, no dropping of output power. The design is designed and rated properly.The dump amp in this thread will only achieve those BS figures under specific conditions. In other words, it isn't an audio amp, it is a specked music amp for only a specific sub-set of songs at specific volumes for specific minuscule periods of time, and, they do not tell which songs to use in the datasheet.

author: themadhippy
author_rank: Super Contributor
timestamp: August 23, 2025, 02:25:54 pm
content: Quoteyou've obviously never played with l'acoustics,

author: bsdphk
author_rank: Regular Contributor
timestamp: August 23, 2025, 02:46:28 pm
content: »I bought a 250w RMS / channel amp, I feed it full volume 1v RMS at the inputs and it will output the specified 250w / channel even with the classical music I listed all day long, no issues, not clipping, no dropping of output power. The design is designed and rated properly.«250W all day long ?Wouldn't it be better for everybody involved if you got hearing-aids ?;-)

author: BrianHG
author_rank: Super Contributor
timestamp: August 23, 2025, 03:01:53 pm
content: Quote from: bsdphk on August 23, 2025, 02:46:28 pmYes, I have gotten the cops called on me a few times.No I do not need a hearing aid.Yes, watching something like Avengers Endgame with more than 30 straight minutes of total chaos rumbling is what I call entertainment. I dont believe in audio systems which cannot work their way through that without a dip in performance.And ok, I also prefer high quality stereo speaker which operate from 25hz to 20khz without separate sub-woofers, though today's junk seems to separate the LFE onto separate channels instead of properly stereo imaged kicks and vibrations in perfect phase with the higher tones.(Yes, I realize that it is possible to get properly phase tuned multi-K$ setups which will do this right and blow my system out, especially everything below 30hz, but I believe in simple refinement over complicity.)

author: paul cotter
author_rank: Regular Contributor
timestamp: August 23, 2025, 07:52:06 pm
content: CaptDon, I cannot remember the Carver model number offhand and I am heading for the airport shortly and will be incommunicado for~10days. I can find the model number when I return home in early sept. What I can tell you is that it used a mains transformer(quite small) with triac control on the input to regulate the three dc supplies.

author: SteveThackery
author_rank: Super Contributor
timestamp: August 24, 2025, 10:48:59 am
content: Quote from: BrianHG on August 23, 2025, 02:05:48 pmSo we agree that I don’t understand, but then you say exactly what I said using different words. All amplifiers have limits - the issue is whether those limits are properly revealed on the labelling. Your example is of an amplifier where it is. There are plenty of amps where it isn't.For example, I can probably buy quite cheaply an amplifier rated on the label at 1000W which won't sustain that output power, but which would perform just as well as your exemplar amp at 250W. All that is needed is an honest test method and honest labelling.

author: SteveThackery
author_rank: Super Contributor
timestamp: August 24, 2025, 10:52:14 am
content: Quote from: BrianHG on August 23, 2025, 02:05:48 pmThat worries me. How can a power in watts be "RMS"? The power waveform is not alternating. Shouldn't it say 250W "continuous"?

author: BrianHG
author_rank: Super Contributor
timestamp: August 24, 2025, 01:32:39 pm
content: Quote from: SteveThackery on August 24, 2025, 10:52:14 amYes, I know, volts are usually measured in RMS. Anyways, many amps give you peak power measurements where the output power is derived from feeding a 'square wave' from power rail to power rail into the specified speaker load, i.e. 8 Ohm.This means that my amp can deliver more than 250w/channel into an 8 ohm load if I feed it a square wave at ~1.5v peak before the amp's voltage rail limits clips the output signal instead of a sine wave at ~1.5v peak which delivers less total power into the 8 ohm load.

author: TimFox
author_rank: Super Contributor
timestamp: August 24, 2025, 02:25:36 pm
content: If you measure rms Volts across a resistor load, the calculatedV2/Ris inmean Watts.If you take the instantaneous voltage, as seen on an oscilloscope, you can calculate the instantaneous power, and calculate the rms value of that power, but that value is useless. For a sinusoidal voltage waveform, the calculated rms power is larger than the (useful) mean power: I am surprised that the fraudulent advertised amplifier power values neglected to use that inflated value.

author: ejeffrey
author_rank: Super Contributor
timestamp: August 25, 2025, 04:39:00 am
content: Quote from: BrianHG on August 23, 2025, 07:21:17 amThanks for giving specific examples that are in the public domain with freely available recordings!I wrote a python script that takes an input file .flac file and computes: 1) the peak instantaneous power, and 2) the maximum average power over intervals from 1 ms to 100 s.I downloaded 24 bit / 96 kHz FLAC files of the 1812 overture and Also Sprach Zarathustrahttps://archive.org/details/lp_1812-overture-op-49-capriccio-italien_pyotr-ilyich-tchaikovsky-the-london-symhttps://archive.org/details/lp_also-sprach-zarathustra-op-30_richard-strauss-eugene-ormandy-the-philadeThe top of the plot is the full-scale output for the file, which neither recording reaches. The blue curve is the highest instantaneous power, derived from the largest magnitude single sample in the whole file. The orange curve is the average power of the highest intensity interval of the specified duration.In both cases, the maximum sustained power has dropped *significantly* already by 10 milliseconds. An amplifier which can produce 100 watt continuously, but can surge to 1 kW for 10-100 milliseconds can reproduce either of these pieces louder without clipping than an amplifier that can produce 250 W sustained average power but with only a 500 W peak.I can't say that these recordings are the best, or that there are no recordings for which that conclusion would be flipped. But in general, if you are producing an audio amplifier for music, you will get more capability per kg and per $ if you design around a high crest factor.In truth these are actually really extreme examples of the opposite of your claim. Despite the qualitative experience of "sustained high loudness" -- both actually maintain high crest factor even at their loudest sections. Heavily compressed audio, such a TV commercials or radio mixes of pop music would probably show lower crest factor when analyzed like this.

author: amyk
author_rank: Super Contributor
timestamp: August 25, 2025, 06:37:03 am
content: Quote from: paul cotter on July 14, 2025, 02:22:45 pmEnvelope tracking?

author: Analog Kid
author_rank: Super Contributor
timestamp: August 25, 2025, 06:45:01 am
content: Quote from: amyk on August 25, 2025, 06:37:03 amNo, sounds like he's describing class G amplification, with multiple switchable power rails.

author: bsdphk
author_rank: Regular Contributor
timestamp: August 25, 2025, 07:33:11 am
content: Quote from: ejeffrey on August 25, 2025, 04:39:00 amSound engineering has two different concepts: "volume" and "loudness".When television ads "sounds much louder" it is not because the volume is higher, but because the loudness is.Two of the most extreme dynamics musical recordings of all time, both get there with loudness rather than volume:Solti's recording of Verdi's Requiem from 1968, has many truly astonishing jumps in loudness, in particular considering that some of them start from a huge choir almost whispering.And young Karajans Othello from 1961, takes a really good turntable and even better speakers to get through the first minute, because of the cannon fired on top of the organ having a great day.If you want an example of raw volume, take Charles Dutoit's recording of Saint-Saëens 3rd from 1982, where the organ will give your amplifier a good workout. When Dolby demo'ed their new sound system for cinemas back in late 1980'ies, this is what they used.

author: Analog Kid
author_rank: Super Contributor
timestamp: August 25, 2025, 07:55:43 am
content: Quote from: bsdphk on August 25, 2025, 07:33:11 amOK, so what's the difference? You omitted to explain that.I know that my amplifiers have a "loudness" switch in addition to a "volume" control, but I don't think that's what you mean here. (The "loudness" switch changes the amp's frequency response, like a fixed-notch tone control.)

author: langwadt
author_rank: Super Contributor
timestamp: August 25, 2025, 08:28:32 am
content: Quote from: Analog Kid on August 25, 2025, 06:45:01 amyes, muliple rails is class-G, variable rail like envelope tracking is class-H

author: SteveThackery
author_rank: Super Contributor
timestamp: August 25, 2025, 12:57:41 pm
content: Quote from: Analog Kid on August 25, 2025, 07:55:43 amActually, that loudness switch simply boosts the low and high frequencies as you turn down the volume, because the sensitivity of our ears falls away faster at those frequencies. Thus the subjective experience of the sound remains more consistent over a wide range of volume levels.

author: SteveThackery
author_rank: Super Contributor
timestamp: August 25, 2025, 01:06:27 pm
content: Quote from: Analog Kid on August 25, 2025, 07:55:43 amI think "loudness" is a subjective experience. Loudness is boosted bynormalisingthe material first - so the peaks are almost but not quite clipped - followed bycompression, in which the quiet bits are boosted, such that the overall experience is of a consistently loud noise with a smaller dynamic range.

author: BrianHG
author_rank: Super Contributor
timestamp: August 25, 2025, 02:06:12 pm
content: Quote from: ejeffrey on August 25, 2025, 04:39:00 amThese versions are a joke, right?Here are some manly versions:(Click on the top right download icon to get the original .zip file)Sprach - Just the introduction (8mb flac)https://drive.google.com/file/d/1OV6PrfNA5CGnGiRpF2XUwKLbuuoxBtUw/1812, full (69mb flac)https://drive.google.com/file/d/1tVUXhqYcWI3OfQi9GyGKt2LKcQGWEJ2J/Yes, the total sustain VS the entire track is small, but, you can do a re-analysis for comparison.Also, don't forget, proper recordings should never peak the full sample range. Just turn up your pre-amp's gain to reach the max.

author: TimFox
author_rank: Super Contributor
timestamp: August 25, 2025, 02:32:11 pm
content: Quote from: SteveThackery on August 25, 2025, 12:57:41 pmThose switches, with their frequency boosts, supposedly use the Fletcher-Munson curves (look it up), originally published in the 1930s, that relate perceived loudness (in “phons”) to physical acoustic level (in dB SPL). However, to work properly, the gain of the system would need calibration, including loudspeaker efficiency, for which the amplifiers have no provision.Note that those curves are relatively flat at high levels, and noticeably strong at low levels.

author: ejeffrey
author_rank: Super Contributor
timestamp: August 26, 2025, 04:25:24 am
content: Quote from: BrianHG on August 25, 2025, 02:06:12 pmYou will have to take that up with the orchestras involved.QuoteThe plot changes in the details, but not enough to matter. The 10 dB point is at 1 second instead of 100 ms. Yout still benefit from an amplifier that can produce a peak power significantly in excess of the sustained power. I put the code into a colab, so feel free to check. Note that I just handle the whole uncompressed file in one array. That's fine for the smaller clips you provided but the ones from archive.org are too big for the memory on the colab VMs, and I couldn't be bothered to break it up into overlapping chunks.https://colab.research.google.com/drive/1QUGw4yDjrQIiMY_GqLsyywk--zT9dWgs#scrollTo=HfJegAUhmZ1a

author: BrianHG
author_rank: Super Contributor
timestamp: August 26, 2025, 08:03:20 am
content: Quote from: ejeffrey on August 26, 2025, 04:25:24 amI think the orchestras didn't go through the expense of using actual cannons like the 1979 versions I provided.Unless your class D amp has some major reservoir caps to sustain those peaks, it would choke on some of the really adjacent cannon firing in my version of 1812 if you crank up the volume.I prefer a system where you need not question such things.As for Sprach Zarathustra, well, I think it was just the strength, size and VLF capable mics in that early 80s recording.

author: Analog Kid
author_rank: Super Contributor
timestamp: August 27, 2025, 02:40:17 am
content: Quote from: BrianHG on August 26, 2025, 08:03:20 amHeh; that reminds me of the many concerts I played with an orchestra doing the 1812. (The actual title of the piece is "Ouverture solennelle 1812".)One year our conductor got a local gun club to provide the "cannon shots" at the end. They brought several cut-open 55-gallon drums on stage, in the back with the percussion section, and at the critical moments fired shotguns into them.KA-BLAMMO!. Smoke in the air and everything.The effect was startling and powerful. But about the fourth time we performed it, it got really old really fast.

author: BrianHG
author_rank: Super Contributor
timestamp: August 27, 2025, 12:19:38 pm
content: Quote from: Analog Kid on August 27, 2025, 02:40:17 amYup, it is a piece of music I reserve for something extra special. I only listen to it once in around 5 years.Really messes with the neighbors as the explosions are deliberately off kilter.

author: madires
author_rank: Super Contributor
timestamp: August 27, 2025, 01:24:08 pm
content: Classical music can be a challenge for some stereo setups.Especially when a high dynamic range is involved. Modern pop/rock recordings are often so compressed/normalized that there are only a few dBs of dynamic range left.

author: BrianHG
author_rank: Super Contributor
timestamp: August 27, 2025, 03:24:50 pm
content: Quote from: madires on August 27, 2025, 01:24:08 pmYup, I still listen to early progressive rock, seeking out the original first CD pressing instead of the remastered garbage. Among my favorites would be albums like Genesis' The Lamb Lies Down On Broadway (Ok, the first early 90's remaster is ok as it never clips or has no compression) or Pink Floyd's Dark Side of the Moon (The Japanese Toshiba Black Triangle CD Pressing version, no BS here, raw sample from the master tapes, no EQ, no volume). These albums dynamic ranges would not be considered listenable in today's society.I also disturbingly heard that some new modern remasters of old albums now also are going through auto-tune. Yes, they are taking classics and making the real original vocals into perfect pitch versions calling that an improvement. Another reason to skip Spotify and Apple Music, how do I know if they are feeding me an original version, or, some modern reprocessed garbage?If you are lucky enough to own original old CD pressings of classics before this modern louder is better and now re-tuned garbage, treasure them, properly back them up and keep em safe.I lost my original CD pressing of Pink Floyd's 'The Wall', all modern 're-mastered' versions are F--ked and I can no longer find anywhere a backup of the originals. All the remastered versions have the vocal choir portions artificially clipped and the sample peaks with their volume brought back down to the wrong levels sounding muted and filled with distortion.My last good copy if from the feature film, but, I lost the ability to just properly play the album. I would have to hunt some or stored with CDs to see if I can get a good copy.

author: langwadt
author_rank: Super Contributor
timestamp: August 27, 2025, 03:33:31 pm
content: Quote from: madires on August 27, 2025, 01:24:08 pmwhich would arguably be worse for an amplifier designed for high crest factor

author: TimFox
author_rank: Super Contributor
timestamp: August 27, 2025, 03:35:44 pm
content: Perhaps the highest dynamic range live concert in my recent history was the Chicago Symphony Orchestra performing "Bluebeard's Castle" by Bartok last February.The first part of the concert, before intermission, was Beethoven's Symphony no. 2, using a much reduced set of musicians.For the Bartok in the second half, the stage was completely filled with musicians, but the full power was reached at "Door Number 5" with full volume.

author: langwadt
author_rank: Super Contributor
timestamp: August 27, 2025, 03:35:59 pm
content: Quote from: BrianHG on August 27, 2025, 03:24:50 pmhttps://www.youtube.com/@wingsofpegasus

author: BrianHG
author_rank: Super Contributor
timestamp: August 27, 2025, 03:51:54 pm
content: Quote from: langwadt on August 27, 2025, 03:35:59 pmYou are only making things worse for me.....

author: themadhippy
author_rank: Super Contributor
timestamp: August 27, 2025, 04:09:55 pm
content: QuoteBomb tanks and maroons is the more traditional option if elf and starzi wont allow real cannonsQuotetotally agree about the remastering aka squeeze every last drop of dynamics out the bugger,but for me those ole classics on vinyl is the only way to enjoy em.

author: BrianHG
author_rank: Super Contributor
timestamp: August 27, 2025, 04:22:33 pm
content: Quote from: themadhippy on August 27, 2025, 04:09:55 pmCareful, vinyl is also compressed, though I would say a warmer experience.Also, if you wanted an all analog path, any vinyl pressings since the late 80's use a sampler, or digital source on their lathes to create the master pressing instead of the old original analog 2-head tape delay technology.

author: themadhippy
author_rank: Super Contributor
timestamp: August 27, 2025, 04:52:45 pm
content: Quoteive a fair few original vinyl and first cd issues of the same album and i cant think of one were cd isnt the poor second cousin,one of my goto comparisons is the pink fairy's version of walk dont run,the kick drum intro on vinyl is a full on artillery assault and the whole track is full of energy,meanwhile the intro on the cd is like being tickled by a moist lettuce and the energy that makes you wanna leap about like a nutter just aint thereQuoteyea but thats modern music for ya

author: Analog Kid
author_rank: Super Contributor
timestamp: August 27, 2025, 10:41:56 pm
content: Quote from: TimFox on August 27, 2025, 03:35:44 pmThat sounds pretty impressive. (Love Bartók, BTW.) Chicago's a great band.For @BrianHG, if you want to listen to some music with really powerful dynamic range, get ahold of a copy of Tchaikovsky's "Francesca da Rimini". (Mine is Lenny Bernstein conducting the Israel Philharmonic, on Deutsche Grammophon.)The great crescendos on thegran cassa(bass drum), followed bytutti fortissimopassages, will stretch your setup's capabilities to its limits.

author: BrianHG
author_rank: Super Contributor
timestamp: August 27, 2025, 11:37:02 pm
content: Quote from: Analog Kid on August 27, 2025, 10:41:56 pmHmm, couldn't find the Israel Philharmonic version, but a Telarc CD version exists:Tchaikovsky: Francesca da Rimini, Op. 32, TH 46 · Baltimore Symphony Orchestra · David ZinmanLets see if I can find an original CD somewhere instead of the YouTube garbage rip.(The 2 .flac pieces I provided earlier are Telarc Rips, known for destroying sound systems.)

author: BrianHG
author_rank: Super Contributor
timestamp: August 27, 2025, 11:39:15 pm
content: Note, Youtube is known for limiting the musical peaks, but just like all Telarc recordings, this one still has a wide dynamic range. (My neighbors are gonna kill me on this one, I can tell...)

author: Analog Kid
author_rank: Super Contributor
timestamp: August 28, 2025, 12:59:11 am
content: Since you seem to like bombastic, loud music (as I do), Brian, here's another one to try:Respighi's Roman Festivals (Feste Romane). Has some crazy exciting passages. (Starts outfff.)Also check out the Infernal Dance of King Kashchei from Stravinsky'sFirebirdsuite.Another one: Bernstein's Symphonic Dances from West Side Story has some very powerful moments (especially the gang-fight sequence), besides just great music overall. My recording is Seiji Ozawa/San Francisco Symphony from the 1970s.

author: BrianHG
author_rank: Super Contributor
timestamp: August 28, 2025, 01:55:13 am
content: My first fiore into classical recordings. This disc goes down to 5hz, guaranteed to blow your system and contains many movie themes for those who want a little more modern music:https://www.amazon.ca/Time-Warp-Erich-Kunzel/dp/B000003CTHTrack list:1 Ascent2 2001/2010: Introduction To Also Sprach Zarathustra-Altered Version3 Star Treck: Main Theme (The Movie)4 The Menagerie: Suite (Original Pilot For The TV Show Star Trek)5 Battlestar Galactica: Main Theme6 Superman: Love Theme7 Star Wars: Throne Room & End Title8 Alien: Closing Title9 2001: On The Beautiful Blue Danube10 2001: Gayne Ballet: Adagio11 Introduction To Also Sprach Zarathustra-Reprise, Original Version