Would it surprise you to learn that is how they've rated power amplifiers for the last 30 or 40 years?
When amplifiers rarely got over 25 watts, most people endured a considerable amount of clipping as par for the course. A 20 watt amp, at the typical 1 or 2 watt living room levels was already clipping on peaks. 10% distortion was typical in those days. They simply took advantage of this to relate bigger numbers.
In fact even the $75.00 mini-amps I bring in for my friends far exceed the specs of similar powered amplifiers even 10 years ago.
Absolutely true. This is real high end audio... at last.
All that's missing is the "audiophile" bling appeal.
Douglas Blake, I moved on from that question.
I don't think the amp will necessarily work with a 48V power supply because some components may blow up when it's subjected to 48V power.
Aliexpress.com sellers don't know much about the amplifiers they sell.
This TPA3255 amp board uses LM2575T-12 voltage regulator, the maximum input voltage of which is 40V. Yet, the seller recommends 48V power supplies for this amp board.
Also, if you want to use 48V power supplies, the main capacitor's maximum input voltage should generally be substantially higher than 48V. If the amp had genuine high-quality brand capacitors, the main capacitors' rated input voltage doesn't have to be substantially higher than that of a power supply. But, I don't trust chinese generic amplifiers much.
I don't think the amp will necessarily work with a 48V power supply because some components may blow up when it's subjected to 48V power.
Aliexpress.com sellers don't know much about the amplifiers they sell.
This TPA3255 amp board uses LM2575T-12 voltage regulator, the maximum input voltage of which is 40V. Yet, the seller recommends 48V power supplies for this amp board.
Also, if you want to use 48V power supplies, the main capacitor's maximum input voltage should generally be substantially higher than 48V. If the amp had genuine high-quality brand capacitors, the main capacitors' rated input voltage doesn't have to be substantially higher than that of a power supply. But, I don't trust chinese generic amplifiers much.
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Douglas Blake & scottjoplin, don't even think of adding NTC 10 ohm if you don't know what you are doing.
On 115V power supply how you will provide enough short circuit current to blow the fuse (in short time 0.4s), device (equipment) will burn and your protection is lost. If you turn your device in cold state, only 11.5A are available, what is not enough to burn fuse instantaneously (term for time lower then 0,4s), it will heat itself and maybe catch fire.
On 230V power supply it is a little better, but you have to have 6A (C) automatic fuse maximum to protect the line feed. Higher fuse rate will not trip in enough short time (time depends on fuse characteristics).
So, careful design is necessary when you design circuits with high inrush current and to fulfill protection demands.
On 115V power supply how you will provide enough short circuit current to blow the fuse (in short time 0.4s), device (equipment) will burn and your protection is lost. If you turn your device in cold state, only 11.5A are available, what is not enough to burn fuse instantaneously (term for time lower then 0,4s), it will heat itself and maybe catch fire.
On 230V power supply it is a little better, but you have to have 6A (C) automatic fuse maximum to protect the line feed. Higher fuse rate will not trip in enough short time (time depends on fuse characteristics).
So, careful design is necessary when you design circuits with high inrush current and to fulfill protection demands.
Thanks pitbul. What level of inrush current of a smps would indicate the presence of protection?
So, if you don't trust them, why are you buying them?
Yes you probably should look inside and confirm part tolerance first. I buy quite a few of these little things for friends (but never from Ali Express or EBay, had too many problems with both) and when I pick up a new model, the covers come off automatically for a full visual inspection.
I generally advise people to stay with the middle range units... don't buy the cheapest and don't overspend on the brand names. There are some very good buys and surprisingly good equipment out there.
Yes there is a crap line here. Below a certain price point you know they have to be using substandard or counterfeit parts. But as I pointed out before, the price of these things has come down a very long way in the last couple of years. For the TPA3116 amps I usually buy that line is around $60.00 Canadian.... not the $600 that it was with old-school amps.
Ask yourself if you need the kind of power the 3255 chip delivers... I don't know anyone who needs more than about 30 or 40 watts per channel in their living room or maybe 10 per channel on their desktop. Even in home theatre settings, 40 or 50 watts per channel should be enough unless you plan to give yourself hearing damage.
Maybe pick up a TPA3116 based amp to start. They are a far more established design and there are numerous very good quality versions available... like this one I have one of these in daily use in my living room and have set several friends up with them. So far not even a hint of problems.
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Wasn't planning on it. I know better since it could destabilize the oscillator startup... as I said.
Inrush current are specific, not clearly indicated, circuit dependent...
I can only mention that inrush current of some LED driver power supply (<100W) is relatively high, about 60Amps, which trips 10A (B) miniature compact circuit breaker instantaneously (MCCB).
Audio power supply's of high power amplifier should have inrush limiting to prevent tripping of circuit breaker installed in house installation. Last explanation is for 230V ac power source.
NTC 10 ohm resistor is much more than feeder impedance and defines circuit by it resistance, as we know that NTC will not drop fast enough to deploy enough short circuit current.
I can only mention that inrush current of some LED driver power supply (<100W) is relatively high, about 60Amps, which trips 10A (B) miniature compact circuit breaker instantaneously (MCCB).
Audio power supply's of high power amplifier should have inrush limiting to prevent tripping of circuit breaker installed in house installation. Last explanation is for 230V ac power source.
NTC 10 ohm resistor is much more than feeder impedance and defines circuit by it resistance, as we know that NTC will not drop fast enough to deploy enough short circuit current.
This is a very valid concern.
As an example, I have a small class-D board I bought from an Amazon seller. The ad. copy claimed it could be run from 36 volts DC, but there are several 32V power rail filter caps on the PCB.
I run it from either a 24V DC SMPS, or a nominally 21-volt battery pack.
-Gnobuddy
I agree 100%. I think many people under-estimate the power of a watt. Mostly this is due to the flooding of the '80s and '90s market with low-efficiency multi-way speakers. Amps had to be appropriately powerful to produce the desired decibels.
But even with "modestly" sensitive speakers (in the high 80s to low 90s) a few (great) watts of amplifier is often plenty. My "summer" amp is TPA3118-based (GMarsh's "Wiener") and I am running it on a linear PS I built myself. It consists of a 12V 40VA AC/AC transformer, a big bridge rectifier, a 3,000uF 50V smoothing cap, and an LM317 regulator module that is only good for about 1.5A. The TPA3118 can handle up to 27V and considerably higher amperage, so this PS would be considered "under-powered" by many. Guess what? It has more than enough (clean!) watts to fill my living room and kitchen areas. It can easily drive my dual-driver EL-70 full range MLTLs beyond their excursion limits. I have run this same amplifier board from a 24V 5A Omron SMPS and there was no advantage at all over my DIY linear supply at listening levels that do not carry the risk of hearing damage.
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Consider first that an 90db speaker produces more sound output on 1 watt than a power lawmower. ( Healthlink )
Most non-destrutive listening actually occurs at 2 watts or less.
So now I have to ask ... exactly how loud is your music that you need more then 100 watts??? 😱
"But I run my 600 watt McIntosh up so the needle goes half way across all the time..."
Mcintosh power meter...
Most non-destrutive listening actually occurs at 2 watts or less.
So now I have to ask ... exactly how loud is your music that you need more then 100 watts??? 😱
"But I run my 600 watt McIntosh up so the needle goes half way across all the time..."
Mcintosh power meter...
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In my experience, amps sold for home Hi-Fi were rarely advertised primarily by their 10% THD output capability; at most, that largely useless figure would be a secondary line in the specs, below the power output at a more representative THD such as 0.1%.
Chip-amps with any ambitions to high quality sound were not advertised at 10% THD either; look at the two attached images, both taken from the May 1999 LM3886 datasheet.
The headline news at the top of the datasheet (first image) is "68 W continuous average output power into 4 ohms at Vcc=+/- 28V". Further down is the graph of THD vs output power, and a close look shows that the THD is about 0.005% at 68 watts output power into a 4 ohm load with +/- 28V supplies.
So Texas Instruments didn't specify a useless output power at 10% THD - in fact they specified their output power at 0.005% THD, spectacularly low, and right before actual clipping starts on the graph, as indicated by the sharp knee in the curve.
Well, we've had audibly perfect audio amps for decades now (all distortions far below the threshold of audibility.) But until the class-D revolution occurred, they were never this small, this light, or this inexpensive!
Stick one in a huge platinum-plated enclosure with solid gold 00-gauge bus-bars for wires and a front panel milled from 1" thick aluminium sheet, and you might be able to sell it for $5000. 🙂
-Gnobuddy
Regarding the misplaced discussion on efficiency (and our corresponding collective "responsibilities") all I have to say is that my "winter" amp (EL34 P-P) pulls a full 300w from the wall regardless of where the volume dial is set, and only produces a few nice music watts at my typical listening levels. Nobody on this earth is going to persuade me not to use it. I do, however, power it down when not in use. 🙂
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My home-designed EL84 stereo amp (capable of 17W/ch) rarely ever get pushed to put out more than "normal room volume" into a pair of Advent Maestro floor-standing speakers.
I'd guess on average about 5 watts/channel would be a bit annoyingly loud to tolerate for me and guests.
Surely we'd have to yell over the music if a conversation were to take place.
TPA3251 and TPA3255 can output up to 50W for each speaker at 0.1% THD with a 32V 5A adapter. I want some headroom even if transients use only a few watts.
An amplifier is like a car. It accelerates and decelerates. An engine that can accelerate up to 50W can momentarily accelerate to 5W and decelerate to 0.5W comfortably.
To make speakers more responsive, speed of acceleration and deceleration becomes important.
A weak amplifier cannot accelerate or decelerate fast.
A car engine capable of running at 200km/h can run a car at 100km/h comfortably.
People drive ferraris in crowded cities because ferraris can accelerate fast when the green light turns on. It's responsive.
Also, some speakers don't respond well to weak amplifiers even though, in theory, they only need 1~2 watts to be loud enough.
If your woofers are not light, your woofers can become more responsive with a stronger amplifier.
An amplifier is like a car. It accelerates and decelerates. An engine that can accelerate up to 50W can momentarily accelerate to 5W and decelerate to 0.5W comfortably.
To make speakers more responsive, speed of acceleration and deceleration becomes important.
A weak amplifier cannot accelerate or decelerate fast.
A car engine capable of running at 200km/h can run a car at 100km/h comfortably.
People drive ferraris in crowded cities because ferraris can accelerate fast when the green light turns on. It's responsive.
Also, some speakers don't respond well to weak amplifiers even though, in theory, they only need 1~2 watts to be loud enough.
If your woofers are not light, your woofers can become more responsive with a stronger amplifier.
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Misplaced indeed. 😱
The biggest energy consumption in our home tends to be heating, cooling, and cooking. Our cars use enormously more energy than our homes. Big trucks that bring us our food and our consumer goods use far more energy than cars. And the even bigger container ships that feed the trucks are estimated to pollute as much as 50 million cars ( Big polluters: one massive container ship equals 50 million cars ).
There are thousands of those container ships on the world's oceans, and more of them every year; I seem to recall having read that the total tonnage of container ships on the ocean doubles every ten years.
Anyone claiming your 300W amp is endangering the planet has no clue how to count decimal places. That 300w amp, all by itself, running 24 hours a day, does in fact use as much energy (7.2 kwh per day) as an entire small efficient house does. BUT - that amount of energy is a tiny, tiny, tiny fraction of the total energy the average first-world occupant is using, directly and indirectly.
It's about 25 years since I first began to pay attention to the science of global climate change. Back then, I did a quick back-of-the envelope calculation: the average human being is a 100-watt, hydrocarbon-burning engine. A small car using only 15 horsepower at a gentle cruise is a 11,000 watt hydrocarbon burning engine - two orders of magnitude more than a person. Floor the throttle, and that 150-horse engine uses three orders of magnitude as much hydrocarbon fuel as the person in it.
Burning hydrocarbons creates CO2, so the simplest, crudest estimate is that a small car emits between one hundred and one thousand times as much CO2 as the person driving it. 😱
Even worse, the person was fueled by recently grown hydrocarbons - vegetation or animals that grew just recently - so the person is essentially just putting back CO2 that was just recently pulled out of the air. The car, on the other hand, is running on fossil fuel, created on average 100 million years ago. So the car is spewing out CO2 today that was originally pulled out of the air 100 million years ago - we're adding ancient CO2 to the atmosphere.
That quick little back-of-the-envelope calculation - that every time the throttle is floored, just one little economy car was spewing out as much CO2 as a thousand of my pre-industrial ancestors - shocked me. I knew we were in big, big trouble; with that huge an increase, there was no way we were going to be able to reduce our CO2 output to anywhere near pre-industrial values, and so there was no way we could avert eventual disaster.
That was in 1993 or so. The next 26 years have only added more evidence to support the conclusion I drew from my original quick-n-dirty calculation: the problem is too big to fix.
-Gnobuddy
The logic within an individual home is correct... your electric blanket draws more... but when you look beyond your personal use, the picture changes quite a bit.
That one TV drawing 1.2 watts in standby is no big deal at all. But for the power grid, 20 million households with a TV drawing 1.2 watts each amounts to 24 Megawatts of energy.
That one TV drawing 1.2 watts in standby is no big deal at all. But for the power grid, 20 million households with a TV drawing 1.2 watts each amounts to 24 Megawatts of energy.
I don't know how you can compare a car with an audio amplifier.
And I respectfully disagree with your saying "A weak amplifier cannot accelerate/decelerate fast. - where did you get that idea?
As a seasoned electronic technician, that doesn't make any sense to me.
I learned it from an audio engineer who also serves as a professor. Because many disciplines are isolated from each other, an electronic technican might not necessarily know about this.