Does anyone know of an organization that actually tests and rates power output for bass amps? I've owned a few lightweight class D amps and not had good results. I have an education in electronics and as i understand electric power physics an amp that only takes in 125 watts from the power source cannot output 2000 watts to a speaker. When i worked in the HiFi industry a long time ago a couple of unaffiliated organizations actually tested amplifiers and published the results. Today bass amp manufacturers seem to just make up power output ratings. I'm getting old and would like to lighten the load in and out but so far everything I've tried can't produce sound levels that match my old heavyweight amps. Thanks for your input.
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actual power output?
- Thread starter TieDye
- Start date
- Feb 12, 2006
- 60,951
- 5
- 220,594
- Disclosures
- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
There is no difference in how class D amps are rated compared with class AB amps.
The problem is that different manufacturers have in fact rated their amps using different metrics (such as "peak" versus "RMS)", or "burst (20mSec versus continuous (or continuous for amplifier purposes). For bass guitar or guitar purposes, THD is nowhere near as important as for other applications because the instruments themselves generate 10X the THD the amp does under linear operation.
You have to use your brain a little bit to sort through the specs, some manufacturers provide comprehensive specs that clearly state how the power is measured and some manufacturers provide almost no information (or information written by the marketing department without control of the engineering folks). I am strongly in the first camp as a designer.
Regarding power input versus power output, what you may be missing is what the safety and EMC regulators require for how power input is calculated. I have done these calculations here many times yet it still seems to be misunderstood.
Let's say an amp is rated for 1000 watts RMS into 4 ohms. The regulators require that the AC power (or current) draw is printed on the back of the amp and it's based on 1/8 of rated audio power, though it can be more IF the amp is designed and intended to be operated at higher than 12.5% duty cycle. 1/8 of 1000 watts is 125 watts (which is 1/8 of rated audio power). Now, the amp and PSU efficiencies must be factored in, a typical class d amp with SMPS is going to be about 85% efficient so the input power is 125/.85 = 147 watts. This is how the power draw number is arrived at. For a typical class AB amp w/ line frequency power supply, the efficiency number is going to be around 50%, so the power draw would be 125/.5 = 250 watts.
Different designers qualify their amps differently. For example, I have (very) detailed specifications for my products, and they are easily understood by professional engineers who design and test amplifier products. They would look like Greek to an average person however. Like the amps themselves, different designers place different levels of importance on different aspects of their products. As a word of caution, I have seen significant mistakes made by magazines that have attempted to measure things that they did not fully understand. This causes folks who don't understand this to draw incorrect conclusions which get perpetuated like a bad rumor.
The problem is that different manufacturers have in fact rated their amps using different metrics (such as "peak" versus "RMS)", or "burst (20mSec versus continuous (or continuous for amplifier purposes). For bass guitar or guitar purposes, THD is nowhere near as important as for other applications because the instruments themselves generate 10X the THD the amp does under linear operation.
You have to use your brain a little bit to sort through the specs, some manufacturers provide comprehensive specs that clearly state how the power is measured and some manufacturers provide almost no information (or information written by the marketing department without control of the engineering folks). I am strongly in the first camp as a designer.
Regarding power input versus power output, what you may be missing is what the safety and EMC regulators require for how power input is calculated. I have done these calculations here many times yet it still seems to be misunderstood.
Let's say an amp is rated for 1000 watts RMS into 4 ohms. The regulators require that the AC power (or current) draw is printed on the back of the amp and it's based on 1/8 of rated audio power, though it can be more IF the amp is designed and intended to be operated at higher than 12.5% duty cycle. 1/8 of 1000 watts is 125 watts (which is 1/8 of rated audio power). Now, the amp and PSU efficiencies must be factored in, a typical class d amp with SMPS is going to be about 85% efficient so the input power is 125/.85 = 147 watts. This is how the power draw number is arrived at. For a typical class AB amp w/ line frequency power supply, the efficiency number is going to be around 50%, so the power draw would be 125/.5 = 250 watts.
Different designers qualify their amps differently. For example, I have (very) detailed specifications for my products, and they are easily understood by professional engineers who design and test amplifier products. They would look like Greek to an average person however. Like the amps themselves, different designers place different levels of importance on different aspects of their products. As a word of caution, I have seen significant mistakes made by magazines that have attempted to measure things that they did not fully understand. This causes folks who don't understand this to draw incorrect conclusions which get perpetuated like a bad rumor.
Julian Hirsch is long passed. He was such a person that did independent testing and reviews on audio products.
Any good tech with a dummy load, scope and signal generator can measure the maximum power output.
It turns out that bass amps are 8X better than the typical perpetual motion machine and we should all be using them to charge our electic cars, thus saving the planet. It's science.
I learned a lot of basic audio from reading Julian Hirsch's explanations of what they were testing for, how the measurements were performed, and why it mattered. I think I read recently that Stereo Review had morphed into a mag for home theater enthusiasts, so there's another landmark of my youth that's gone the way of the wax cylinder.
Last edited:
- Feb 12, 2006
- 60,951
- 5
- 220,594
- Disclosures
- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
Now measuring accurately and understanding what’s actually being measured is another story.
audiosciencereview.com do lots of measurements of hifi audio gear and have an Audio Precision and a Klippel NFS. The site owner is an EE. The measurements are far more comprehensive than JH could ever do, because of advancements in technology over the years.
I don't know if they'd be interested in measuring MI gear, but you could join and ask.
Steve Meade Designs has a YouTube channel where he test power claims and actual performance of car audio, but he also sells the test equipment that works on all equipment (car, home hifi, PA, bass, guitar, tube, solid state a, A/B, D, H, etc) if you're so inclined to bench test yourself. Add a Kill-A-Watt between your amp and the wall outlet and you could compare power in vs power out.
I don't know of anyone doing this currently with musician gear, but the concept is interesting enough I would quickly subscribe to anyone who made a YouTube channel conducting such tests.
I don't know of anyone doing this currently with musician gear, but the concept is interesting enough I would quickly subscribe to anyone who made a YouTube channel conducting such tests.
My 800W labeled Mesa into my 212 produces more measured dB than the 1,000W Crest power amp into a 2-15 (EV) plus 4-12 stack I used to run. It's not the Watts. It's not the Ohms. It's not even the tort. It's the decibels.
D
Deleted member 165050
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Not sure anyone I know of is claiming to produce 2000 watts from 125 watts, but anyway P=VI is all you need to know.
D
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drumvsbass
Commercial User
- Aug 20, 2011
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- I work for Long and McQuade Musical Instruments Canada in Sales.
^^This^^ and not just different manufacturers. Same Same.
Explain how the Ampeg PF350 is 50 Watts more powerful than an Ampeg SVT in terms of loudness... plug into both and feel the difference.
D
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Your tube amp can be run further into clipping before it sounds bad. This has been know for a very long time, and has given rise to people using terms like "tube watts". Hence it sounds louder on actual music with transients and such. If you run sine waves through the rig, the PF 350 would win by a nose.
- Feb 12, 2006
- 60,951
- 5
- 220,594
- Disclosures
- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
Of course... unless the solid state amp is designed (and executed well) to reproduce the overload characteristics of a tube amp, the gap narrows considerable.
I don't think I run any of my amps so hard that these figures matter to me. A 100w combo does what I think it should do and a 700w head for my use is basically not going to break a sweat.
I suppose it's good to know and it would be good if there was a standard so things could be compared easily.
I suppose it's good to know and it would be good if there was a standard so things could be compared easily.
