AM broadcast transmitters have to run full power 24/7. They're much more robustly built than any audiophile amplifier. That's why a 1kW transmitter takes up a full EIA rack, whereas an 18kW (Powersoft K20) audio amplifier takes 1 only rack unit of space.
I remember when I got my Phase Linear D-500 in the 1970s, the manual talked about why I needed 505 w/ch, stating that peaks can reach 500W when the average power was only 67W. Again, that's in close agreement with the published statement I read years ago that says the crest factor for music program is 9dB.
That's how these tiny class D amplifiers get away with claiming such high output power. But they would all fall down if they had to reproduce an organ pedal tone (like the one opening the Bach "Passacaglia and Fugue in C minor" that goes on for more than 45 seconds).
I remember when I got my Phase Linear D-500 in the 1970s, the manual talked about why I needed 505 w/ch, stating that peaks can reach 500W when the average power was only 67W. Again, that's in close agreement with the published statement I read years ago that says the crest factor for music program is 9dB.
That's how these tiny class D amplifiers get away with claiming such high output power. But they would all fall down if they had to reproduce an organ pedal tone (like the one opening the Bach "Passacaglia and Fugue in C minor" that goes on for more than 45 seconds).
My thoughts:
1] Never try to compare these types of amplifier specs unless they are done using the same test protocol on the same test stand. Heck, some manufactures use different test protocols on different price lines so the expensive amps (with the same circuit) look better.
2] A 15 Amp circuit can deliver 150 Amps for a good fraction of a second. Old-fashioned light bulbs draw 10 times their rated current at turn-on.
3] Way high output power for good fraction of a second depends on:
a] DC supply voltage. It takes high DC voltage for high output power.
b] Loudspeaker/load impedance.
c] Large DC supply capacitors.
1] Never try to compare these types of amplifier specs unless they are done using the same test protocol on the same test stand. Heck, some manufactures use different test protocols on different price lines so the expensive amps (with the same circuit) look better.
2] A 15 Amp circuit can deliver 150 Amps for a good fraction of a second. Old-fashioned light bulbs draw 10 times their rated current at turn-on.
3] Way high output power for good fraction of a second depends on:
a] DC supply voltage. It takes high DC voltage for high output power.
b] Loudspeaker/load impedance.
c] Large DC supply capacitors.
Output power isn't exclusively dependent on high supply voltage. If the load is 1 ohm, even moderate supply voltages, high current-capable, can deliver a lot of power. Power is the product of voltage and current. You need both.
Capacitors store energy. The instantaneous discharge power can be enormous (for example, shorting the terminals with a screwdriver can melt the screwdriver). This is where amplifiers can derive high 'dynamic' power capacity. As long as there's enough current to fully charge the capacitor between discharges, ie., kick drum beats, then the dynamic short term power output can exceed the continuous rating of the wall outlet.
Inrush current for things like electric motors can be enormous, too. Circuit breakers will support many times their rating for short durations for the reason that it avoids nuisance tripping on such loads.
Capacitors store energy. The instantaneous discharge power can be enormous (for example, shorting the terminals with a screwdriver can melt the screwdriver). This is where amplifiers can derive high 'dynamic' power capacity. As long as there's enough current to fully charge the capacitor between discharges, ie., kick drum beats, then the dynamic short term power output can exceed the continuous rating of the wall outlet.
Inrush current for things like electric motors can be enormous, too. Circuit breakers will support many times their rating for short durations for the reason that it avoids nuisance tripping on such loads.
When in doubt, I try to find a picture of the inside and count the output transistors, look at the power supply, and maybe try to get a clue as to the fuse size, rail voltage.
That will quickly separate the chaff from the wheat.
The carver amps that had high rail voltages, along with high output ratings never impressed me.
As was mentioned, ratings can be had from various methods.
A 1,000hz test signal is different than what music will be like, keep that in mind.
These considerations will be for conventional class a/b amps, class d are a different animal.
That will quickly separate the chaff from the wheat.
The carver amps that had high rail voltages, along with high output ratings never impressed me.
As was mentioned, ratings can be had from various methods.
A 1,000hz test signal is different than what music will be like, keep that in mind.
These considerations will be for conventional class a/b amps, class d are a different animal.
Last edited:
Carver's amplifiers were mainly Class H/G designs with commutating voltage rails that followed signal levels. Many of them sounded good and delivered a lot of power, but I feel that they can't quite deliver the peak current for large industrial speaker systems. For that, I always look to QSC Powerlight amplifiers. Just the fact that the power cords are 7/8" in diameter and have 30A twist lock plugs, indicated that this is in a different class than the 15A consumer plug stuff.
FTC amp ratings happened in 1974. The trouble is, marketers will always game the system. Volts RMS is no better than Watts RMS.
Here is from a porcupine tree album deadwing, song halo - looks more like pink noise than music, and the spectrum peaks at roughly -8dB
Attachments
I've seen this everywhere, and this is the definition of marketing BS. Who really buys a 5.1 or 7.1 receiver and only drives one or two channels? I find it extremely strange.
Also, what on earth does "Discrete Direct Energy" mean? I wish they would just say what chips, transistors, or mosfets they use... Heck, even the amplifier class would be nice..
If you want 8 solid channels of 100W, you are looking at perhaps 100lb of linear power supply, heat sinks etc for a typical class ab design.
You can get away with less heatsinking for class D. OR you can take advantage of statistics and undersize everything except L-C-R in an AB amp.
Oh I'm aware. A high quality 150VA transformer can sometimes be 10 pounds. Truly driving 1000W of RMS class AB audio power would require a massive transformer, which is usually only found in rackmount cases or discrete power supplies.
I'm curious if this has anything to do with car audio amplifiers being rated so much higher. I guess that a 1000 CCA Lead acid battery is a substitute to a 1KVA transformer, so car amplifiers do not need to be massive since they can draw large amounts of current directly from the battery.
Home theatre amplifiers on the other hand need a discrete power supply, and since these are generally more expensive, it's harder to make a cost effective, high wattage amplifier that uses mains voltage.
Maybe if everyone had high current DC mains at home, we'd have higher wattage home amplifiers, haha!
It certainly makes sense to me.
Certainly the cost of the power supply factors in the cost per watt. The fact that high power car audio amps are rated into 2 or 1 ohm and generally additionally inflate by a factor of 2 leads to the high numbers,
Nah.
The worst an amp can do is square waves, which are double the power of the equivalent peak voltage sine wave.
So, an amp rated for 30w (sine wave) output will do 60w square waves, and would cook a 50w speaker. A 300w speaker would laugh at it.
Chris
It's bull and anyone that's taken a high school physics class knows it's bull.
My experience is that they don't believe it.
Bingo. BUT - a square wave is like feeding DC to the woofer and it can really heat up the voice coil.
And it's my experience that a LOT of people love the sound of square waves. 😀 So many people turn my system WAY up when they see it. I immediately turn it down and ask "can't you hear the distortion?" to which they retort "No, it sounds great."
And now I have a blown tweeter of unknown make/model which I hope to replace with some Dynavox domes I ordered. I'm also building a preamp with a lot of the controls on the back because of this. You'll only be able to turn it up so loud or boost the bass so much. Baffle step and low pass filter will only be accessed from the back, and there will also be a secret squirrel volume control on the back.
Porcupine Tree is pretty good for audio quality as far as rock goes, too. In Absentia was mastered a lot better but still, your example is far from the worst of modern music.
Great points being made here. I can see that some of us understand the reality of home "hi-fi" sound reproduction.
On many, many modern recordings, every single track is equalized and compressed differently. The engineer is listening to the mix on a pair of studio monitors and is mixing the tracks so it sounds good on those monitors. It's important that he can hear every track clearly and how it sounds with the other tracks. How it sounds on a mid-fi or a hi-fi will be completely different, and he's probably thinking about that too.
So what is hi-fi then? The vast majority of recordings are fake sound anyway. How do you know if it's being reproduced faithfully?
Different people are different. To my ears, distortion/clarity and dynamic range are important. Frequency response anomalies are secondary, however the frequency range has to be balanced (weak bass with crystal clear mids/highs just sounds weak to me). Some people just like it loud with boom and sizzle, which I can't stand unless it's clean. Some people are satisfied with a $100 tabletop mid-fi.
The speakers I'm currently using are modified 8" 2-way "point source" monitor-like units. They are crystal clear; acoustic tracks (like jazz) are very convincing. Audience noises on live recordings often startle me because I think someone is in the room. They have enough oomph that you can boost the bass, turn them up, and rock out. On the other hand, I have a salvaged "boom box" tabletop "hi-fi" for my computer sound. The speakers are small, ported, and very underdamped to give it some boom-boom. They're equalized as hell by the manufacturer (Philips-Magnavox) to give a balanced sound. They actually do sound loud and clear except for the bass. Most people think they're awesome.
So which one is hi-fi? Both? Neither?
On many, many modern recordings, every single track is equalized and compressed differently. The engineer is listening to the mix on a pair of studio monitors and is mixing the tracks so it sounds good on those monitors. It's important that he can hear every track clearly and how it sounds with the other tracks. How it sounds on a mid-fi or a hi-fi will be completely different, and he's probably thinking about that too.
So what is hi-fi then? The vast majority of recordings are fake sound anyway. How do you know if it's being reproduced faithfully?
Different people are different. To my ears, distortion/clarity and dynamic range are important. Frequency response anomalies are secondary, however the frequency range has to be balanced (weak bass with crystal clear mids/highs just sounds weak to me). Some people just like it loud with boom and sizzle, which I can't stand unless it's clean. Some people are satisfied with a $100 tabletop mid-fi.
The speakers I'm currently using are modified 8" 2-way "point source" monitor-like units. They are crystal clear; acoustic tracks (like jazz) are very convincing. Audience noises on live recordings often startle me because I think someone is in the room. They have enough oomph that you can boost the bass, turn them up, and rock out. On the other hand, I have a salvaged "boom box" tabletop "hi-fi" for my computer sound. The speakers are small, ported, and very underdamped to give it some boom-boom. They're equalized as hell by the manufacturer (Philips-Magnavox) to give a balanced sound. They actually do sound loud and clear except for the bass. Most people think they're awesome.
So which one is hi-fi? Both? Neither?
How poorly music is mastered has nothing to do with how an amp should be power rated
Maybe it could be related to how the amp is used. If you have "music" with an 8 dB crest factor then you don't need much headroom or power. Compressed audio is made to sound good on feeble equipment.
Maybe it could be related to how the amp is used. If you have "music" with an 8 dB crest factor then you don't need much headroom or power. Compressed audio is made to sound good on feeble equipment.
I agree there will always be cheating, but I disagree that Volts RMS in no better.
For one thing, you don't end up with the huge numbers like you do with power ratings. DIN vs ASA was similar, and the DIN scale was less "exaggerated", if you will. E.G. An amplifier that can deliver 16V RMS into 8 ohms vs an amplifier that can deliver 32V RMS into 8 ohms. Or - an amplifier rated at 32 Watts vs and amplifier rated at 128 Watts. 16 vs 32 (twice as much), or 32 vs 128 (4X as much!). Which sounds bigger? Same amplifiers, just volts vs Watts.
And rating amplifiers as volts RMS into different loads doesn't change the numbers much. You might have an amp that can supply 32V RMS into 8 ohms, or 30.4V RMS into 4 ohms, and 28V RMS into 3 ohms. That gives you some idea of the power supply, whereas rating the same output in Watts isn't so easy to see the droop.
I know it's not going happen, but it would be better.
Yep, it works fine for elevators and general background duties but over-compressed music sounds like crap if you turn it up a bit.
In an amplifier, volts means nothing without an impedance, and power means nothing without an impedance.
If I have two amps, both are capable of 20V at 8 ohms but one of them will do 19.5V at 2 ohms and the other will only do 5V without shutting down. If they were rated at 20V RMS / 8 ohms they would both look like the same "voltage" amp. Plenty of room for specsmanship games. Volts is no better as a metric.
Specifying RMS power @ load impedance and distortion over a frequency range is just fine. You just have to know that amps that omit even one of those factors (or use a 1kHz figure, or don't say RMS) are playing specsmanship games.
- Status
- Not open for further replies.