Hi this is River, I am an audio-nut or audiophile in the competition lanes. No this isn't a rant about how much power I have this is a rant about the general public and how easily they are to become sheep on the prairie of consumable goods.
Long and short of it is that people want to believe that the money they spend equals a good investment in there blood and sweat. This creates pride and pride makes people think irrationally.
Now to the meat of the matter, this is a rant specifically on the usage of power in relation to the output of a said device. Most electronics have 2 power ratings; 1 being that of continuous output over a regular interval of time which is often referred to as RMS; Root Mean Square. The 2nd is peak power or output, a 1/1000 of a second burst of time. As with the 1st it is explained below:
In mathematics, the root mean square (abbreviated RMS or rms), also known as the quadratic mean, is a statistical measure of the magnitude of a varying quantity. It is especially useful when variates are positive and negative, e.g., sinusoids. RMS is used in various fields, including electrical engineering.
It can be calculated for a series of discrete values or for a continuously varying function. The name comes from the fact that it is the square root of the mean of the squares of the values. It is a special case of the generalized mean with the exponent p = 2.
The RMS value of a set of values (or a continuous-time waveform) is the square root of the arithmetic mean (average) of the squares of the original values (or the square of the function that defines the continuous waveform).
The RMS over all time of a periodic function is equal to the RMS of one period of the function. The RMS value of a continuous function or signal can be approximated by taking the RMS of a series of equally spaced samples. Additionally, the RMS value of various waveforms can also be determined without calculus, as shown by Cartwright.[1]
In the case of the RMS statistic of a random process, the expected value is used instead of the mean.
Average electrical power
Electrical engineers often need to know the power, P, dissipated by an electrical resistance, R. It is easy to do the calculation when there is a constant current, I, through the resistance.
Amplifier power efficiency
The electrical efficiency of an electronic amplifier is the ratio of mean output power to mean input power. The efficiency of amplifiers is of interest when the energy used is significant, as in high-power amplifiers, or when the power-supply is taken from a battery, as in a transistor-radio.
Efficiency is normally measured under steady-state conditions with a sinusoidal current delivered to a resistive load. The power output is the product of the measured voltage and current (both RMS) delivered to the load. The input power is the power delivered by the DC supply, i.e. the supply voltage multiplied by the supply current. The efficiency is then the output power divided by the input power, and it is always a number less than 1, or, in percentages, less than 100. A good radio frequency power amplifier can achieve an efficiency of 60–80%.[2]
Other definitions of efficiency are possible for time-varying signals. As discussed, if the output is resistive, the mean output power can be found using the RMS values of output current and voltage signals. However, the mean value of the current should be used to calculate the input power. That is, the power delivered by the amplifier supplied by constant voltage VCC is
CEA2006 is the long-awaited rating standard that makes it easy for costumers to compare amplifiers. It defines characteristics that describe the performance of amplifiers designed for mobile applications and replaces the old standard EIA 517B.
According to the standard some specific ratings must appear on the package of the amplifier. The CEA-logo then declares that these specifications are accurate and comparable.
Since the two most fundamental qualities of an amplifier are how loud it will play and how good it will sound, the two principal ratings, according to CEA2006, are Output Power and Signal-to-Noise Ratio. These two quantities are the most significant indicators of an amplifier’s performance.
A car amplifier’s job is to convert power available from the battery into power sent to the speaker. A low-voltage signal, sent from the head unit, is converted into a high-voltage signal, which can deliver more current to the speaker. Ideally an amplifier should be a perfect voltage generator that maintains the output signal, regardless of connected load. A change in impedance should not affect the voltage-signal. Hence, decrease in impedance requires increase in output power. However, since a loudspeaker is not a simple resistor this is a complex task. The perfect amplifier should not care about the connected load, but always generate a constant undistorted output signal.
The fact that different manufacturers, when rating amplifiers, state output power at various supply voltage, load impedance and levels of distortion, makes it impossible to compare the amplifiers according to these measurements.
Primary Output Power should, according to CEA2006, be measured with 14.4V DC supply, a 4-ohm load and with 1% or less total harmonic distortion in the output. Other specifications included in the standard involve different impedances and supply voltages. This is where the manufacturer can indicate the conditions which make their amplifier perform optimally.
Since a loud speaker is much more complex than a resistor, it is not accurate to do measurements only using the rated resistive load (typically 8 ohms). This may result in harmonic distortion and strictly reduced voltage when connecting a real-life loudspeaker to the amplifier.
So that section explains continuous power which is essentially what the amplifier will do all the time under the right conditions with the correct amount of power and ventilation.
Peak power for amplifiers is for all intentions an “Imaginary Number”. We used to say 19 years ago when I sold high end home audio gear “peak on this amp is ____ watts while your standing in a bucket of water with no laces in your shoes for 1/1000 of a second”. We said this or similar to explain that your not spending this money on peak power and how loud it will play the few times in your life that you try to go deaf. Your buying this Crown amplifier because it sound exceptional at listening levels.
Peak power actually has more power than stated above or on the box, it’s a big number and people are impressed by big things and powerful means not small numbers and even use of it. If I told you that my F150 seats 5 full size adults comfortably and has 10 cup holders you might be impressed, but if I told you I can drive through a Honda Accord at 50 mph with only small scratches on my chrome bumper, that would for sure impress you. My wife did it and the guy was uninsured, my bumper still looks great.
In truth I have no idea to the number my Boston Acoustics amp has for peak power. The manufacturer said, “what’s it matter, your smart enough to know it doesn’t matter”.
If you go online and look up an ad on a page like www.sonicelectronix.com , you will notice a lot of lower end brands will try to sell you on peak outputs, not what the amp actually delivers but the real power. Buying good to better gear you will find that you will spend about $.70 to $1.00 for a watt of power. Not to say you can’t get more for the buck, but that is usually true. The true is gonna be hard for you of you to except, there are a lot of brands on the market today that are good at deceiving you into thinking that you are buying a lot for so very little. “I bought this Koiiler 1000 watt amp for like $100.00 bucks, what a deal”. Or “it must have 200 watts a channel, it says so on the box”. Many low end brands will deliver great output for driving subs. I have been telling my friends for years that dirty amp(low end stuff with lots of noise) often make great sub amps.
Amps come in a variety of types and configurations as seen below:
Power amplifier circuits (output stages) are classified as A, B, AB and C for analog designs, and class D and E for switching designs based upon the conduction angle or angle of flow, Θ, of the input signal through the (or each) output amplifying device, that is, the portion of the input signal cycle during which the amplifying device conducts. The image of the conduction angle is derived from amplifying a sinusoidal signal. (If the device is always on, Θ = 360°.) The angle of flow is closely related to the amplifier power efficiency. The various classes are introduced below, followed by more detailed discussion under individual headings later on.
Class A
100% of the input signal is used (conduction angle Θ = 360° or 2π); i.e., the active element remains conducting[6] (works in its "linear" range) all of the time. Where efficiency is not a consideration, most small signal linear amplifiers are designed as class A. Class A amplifiers are typically more linear and less complex than other types, but are very inefficient. This type of amplifier is most commonly used in small-signal stages or for low-power applications (such as driving headphones). Subclass A2 is sometimes used to refer to vacuum tube class A stages where the grid is allowed to be driven slightly positive on signal peaks, resulting in slightly more power than normal class A (A1; where the grid is always negative[7]), but incurring more distortion.
Class B
50% of the input signal is used (Θ = 180° or π; i.e., the active element works in its linear range half of the time and is more or less turned off for the other half). In most class B, there are two output devices (or sets of output devices), each of which conducts alternately (push–pull) for exactly 180° (or half cycle) of the input signal; selective RF amplifiers can also be implemented using a single active element.
These amplifiers are subject to crossover distortion if the transition from one active element to the other is not perfect, as when two complementary transistors (i.e., one PNP, one NPN) are connected as two emitter followers with their base and emitter terminals in common, requiring the base voltage to slew across the region where both devices are turned off.[8]
Class AB
Here the two active elements conduct more than half of the time as a means to reduce the cross-over distortions of class B amplifiers. In the example of the complementary emitter followers a bias network allows for more or less quiescent current thus providing an operating point somewhere between class A and class B. Sometimes a figure is added (e.g., AB1 or AB2) for vacuum tube stages where the grid voltage is always negative with respect to the cathode (class AB1) or may be slightly positive (hence drawing grid current, adding more distortion, but giving slightly higher output power) on signal peaks (class AB2). Solid state class AB amplifier circuits are one of the most popular amplifier topologies used today.
Class C
Less than 50% of the input signal is used (conduction angle Θ < 180°). The advantage is potentially high efficiency, but a disadvantage is high distortion.
Class D
Main article: Switching amplifier
These use switching to achieve a very high power efficiency (more than 90% in modern designs). By allowing each output device to be either fully on or off, losses are minimized. The analog output is created by pulse-width modulation; i.e., the active element is switched on for shorter or longer intervals instead of modifying its resistance. There are more complicated switching schemes like sigma-delta modulation, to improve some performance aspects like lower distortions or better efficiency.
Additional classes
There are several other amplifier classes, although they are mainly variations of the previous classes. For example, class G and class H amplifiers are marked by variation of the supply rails (in discrete steps or in a continuous fashion, respectively) following the input signal. Wasted heat on the output devices can be reduced as excess voltage is kept to a minimum. The amplifier that is fed with these rails itself can be of any class. These kinds of amplifiers are more complex, and are mainly used for specialized applications, such as very high-power units. Also, class E and class F amplifiers are commonly described in literature for radio frequencies applications where efficiency of the traditional classes in are important, yet several aspects not covered elsewhere (e.g.: amplifiers often simply said to have a gain of x dB - so what power gain?) deviate substantially from their ideal values. These classes use harmonic tuning of their output networks to achieve higher efficiency and can be considered a subset of Class C due to their conduction angle characteristics.
When choosing an amp it should be done on the merit of the basics:
I needed an amp to power my woofer. The woofer is a 12” dual 2 ohm design and has a continuous rating of 750 watts total and the power delivered should not exceed 1500 watts or peak. I was also thinking about getting a second 12” woofer in the future, a total of 2 woofers but 4 voice coils. Which would lead to either a 2 ohm total load with both woofers or a 8 ohm load so for this I either needed an amp that could play well at 2 ohms mono or 4 ohms bridged. So I chose the amp that plays well at 4 ohms for the future or 2 ohms now. This amp required 2 4 gauge power wires and 2 4 gauge ground wires and a lot of amperage to run. Since this wasn’t the only amp I would be using and I was going to have other devices, go big.
With this decision comes a price, the price included buying gear. 100 farads of capacitance & 0 gauge wire to support the load in addition, various accessories and some studying up on the car I was gonna use. I had to upgrade the electrical under the hood, add circuit breakers and ensure I followed safety proto-calls to the letter. All this was to ensure:
This is explained best with this. I have speakers that will only need 50 watts of power to play at high volume when I call for it, most of the time the power to them at listening volume is about 20 watts per channel. I have front and rear speakers and am going to incorporate 3 way speakers in the front and the best way to power them is to “Bi-amp” them. This is to say that 2 channels will drive the mids and tweeters and 2 channels will drive the mid-bass drivers. So a 4 channel isn’t enough, so I used a 6 channel with about 55 watts per channel. This amp is perfect for my needs but a poor choice to run subs even though it has many channels and lots of clean pure sound.
When choosing an amp select it for the type that best fits the need matched with the class that best fits your need and pocketbook.
Their car many amps out there and a lot of good stuff, but most of it is crap. Sure this is my opinion, but it is backed up with experience and facts too.
To end this rant for now, I will say this. If you’re gonna brag about how much power you have or how cool your amp looks because it has dancing lights on it or its painted the same color as your car be ready to be circled. When I buy, I buy on the facts above and on if it will fit in my budget and car for that matter.
I have A/D/S for my 6 channels and Boston Acoustics for my sub. A/D/S has set the benchmark for high end home and car audio for 25 years and is widely coveted today by audiophiles around the world.
Later I will rant about speaker power output. Did you know 5 watts is really loud?
Long and short of it is that people want to believe that the money they spend equals a good investment in there blood and sweat. This creates pride and pride makes people think irrationally.
Now to the meat of the matter, this is a rant specifically on the usage of power in relation to the output of a said device. Most electronics have 2 power ratings; 1 being that of continuous output over a regular interval of time which is often referred to as RMS; Root Mean Square. The 2nd is peak power or output, a 1/1000 of a second burst of time. As with the 1st it is explained below:
RMS
It can be calculated for a series of discrete values or for a continuously varying function. The name comes from the fact that it is the square root of the mean of the squares of the values. It is a special case of the generalized mean with the exponent p = 2.
The RMS value of a set of values (or a continuous-time waveform) is the square root of the arithmetic mean (average) of the squares of the original values (or the square of the function that defines the continuous waveform).
The RMS over all time of a periodic function is equal to the RMS of one period of the function. The RMS value of a continuous function or signal can be approximated by taking the RMS of a series of equally spaced samples. Additionally, the RMS value of various waveforms can also be determined without calculus, as shown by Cartwright.[1]
In the case of the RMS statistic of a random process, the expected value is used instead of the mean.
Average electrical power
Electrical engineers often need to know the power, P, dissipated by an electrical resistance, R. It is easy to do the calculation when there is a constant current, I, through the resistance.
Amplifier power efficiency
The electrical efficiency of an electronic amplifier is the ratio of mean output power to mean input power. The efficiency of amplifiers is of interest when the energy used is significant, as in high-power amplifiers, or when the power-supply is taken from a battery, as in a transistor-radio.
Efficiency is normally measured under steady-state conditions with a sinusoidal current delivered to a resistive load. The power output is the product of the measured voltage and current (both RMS) delivered to the load. The input power is the power delivered by the DC supply, i.e. the supply voltage multiplied by the supply current. The efficiency is then the output power divided by the input power, and it is always a number less than 1, or, in percentages, less than 100. A good radio frequency power amplifier can achieve an efficiency of 60–80%.[2]
Other definitions of efficiency are possible for time-varying signals. As discussed, if the output is resistive, the mean output power can be found using the RMS values of output current and voltage signals. However, the mean value of the current should be used to calculate the input power. That is, the power delivered by the amplifier supplied by constant voltage VCC is
CEA-2006
CEA2006 is the long-awaited rating standard that makes it easy for costumers to compare amplifiers. It defines characteristics that describe the performance of amplifiers designed for mobile applications and replaces the old standard EIA 517B.
According to the standard some specific ratings must appear on the package of the amplifier. The CEA-logo then declares that these specifications are accurate and comparable.
Since the two most fundamental qualities of an amplifier are how loud it will play and how good it will sound, the two principal ratings, according to CEA2006, are Output Power and Signal-to-Noise Ratio. These two quantities are the most significant indicators of an amplifier’s performance.
A car amplifier’s job is to convert power available from the battery into power sent to the speaker. A low-voltage signal, sent from the head unit, is converted into a high-voltage signal, which can deliver more current to the speaker. Ideally an amplifier should be a perfect voltage generator that maintains the output signal, regardless of connected load. A change in impedance should not affect the voltage-signal. Hence, decrease in impedance requires increase in output power. However, since a loudspeaker is not a simple resistor this is a complex task. The perfect amplifier should not care about the connected load, but always generate a constant undistorted output signal.
The fact that different manufacturers, when rating amplifiers, state output power at various supply voltage, load impedance and levels of distortion, makes it impossible to compare the amplifiers according to these measurements.
Primary Output Power should, according to CEA2006, be measured with 14.4V DC supply, a 4-ohm load and with 1% or less total harmonic distortion in the output. Other specifications included in the standard involve different impedances and supply voltages. This is where the manufacturer can indicate the conditions which make their amplifier perform optimally.
Since a loud speaker is much more complex than a resistor, it is not accurate to do measurements only using the rated resistive load (typically 8 ohms). This may result in harmonic distortion and strictly reduced voltage when connecting a real-life loudspeaker to the amplifier.
Peak power
Peak power for amplifiers is for all intentions an “Imaginary Number”. We used to say 19 years ago when I sold high end home audio gear “peak on this amp is ____ watts while your standing in a bucket of water with no laces in your shoes for 1/1000 of a second”. We said this or similar to explain that your not spending this money on peak power and how loud it will play the few times in your life that you try to go deaf. Your buying this Crown amplifier because it sound exceptional at listening levels.
Peak power actually has more power than stated above or on the box, it’s a big number and people are impressed by big things and powerful means not small numbers and even use of it. If I told you that my F150 seats 5 full size adults comfortably and has 10 cup holders you might be impressed, but if I told you I can drive through a Honda Accord at 50 mph with only small scratches on my chrome bumper, that would for sure impress you. My wife did it and the guy was uninsured, my bumper still looks great.
In truth I have no idea to the number my Boston Acoustics amp has for peak power. The manufacturer said, “what’s it matter, your smart enough to know it doesn’t matter”.
If you go online and look up an ad on a page like www.sonicelectronix.com , you will notice a lot of lower end brands will try to sell you on peak outputs, not what the amp actually delivers but the real power. Buying good to better gear you will find that you will spend about $.70 to $1.00 for a watt of power. Not to say you can’t get more for the buck, but that is usually true. The true is gonna be hard for you of you to except, there are a lot of brands on the market today that are good at deceiving you into thinking that you are buying a lot for so very little. “I bought this Koiiler 1000 watt amp for like $100.00 bucks, what a deal”. Or “it must have 200 watts a channel, it says so on the box”. Many low end brands will deliver great output for driving subs. I have been telling my friends for years that dirty amp(low end stuff with lots of noise) often make great sub amps.
Amplifiers
- 1 channel or mono-blocks
- 2 channel amps which bridge to 1 channel
- 3 channel amps (one of my favorite)
- 4 channel amps which can do 2 channel or 3 channel
- 5 channel amps which typically are front, rear and sub
- Multi-channel amps which go up to 8 channels or more
Power amplifier circuits (output stages) are classified as A, B, AB and C for analog designs, and class D and E for switching designs based upon the conduction angle or angle of flow, Θ, of the input signal through the (or each) output amplifying device, that is, the portion of the input signal cycle during which the amplifying device conducts. The image of the conduction angle is derived from amplifying a sinusoidal signal. (If the device is always on, Θ = 360°.) The angle of flow is closely related to the amplifier power efficiency. The various classes are introduced below, followed by more detailed discussion under individual headings later on.
Class A
100% of the input signal is used (conduction angle Θ = 360° or 2π); i.e., the active element remains conducting[6] (works in its "linear" range) all of the time. Where efficiency is not a consideration, most small signal linear amplifiers are designed as class A. Class A amplifiers are typically more linear and less complex than other types, but are very inefficient. This type of amplifier is most commonly used in small-signal stages or for low-power applications (such as driving headphones). Subclass A2 is sometimes used to refer to vacuum tube class A stages where the grid is allowed to be driven slightly positive on signal peaks, resulting in slightly more power than normal class A (A1; where the grid is always negative[7]), but incurring more distortion.
Class B
50% of the input signal is used (Θ = 180° or π; i.e., the active element works in its linear range half of the time and is more or less turned off for the other half). In most class B, there are two output devices (or sets of output devices), each of which conducts alternately (push–pull) for exactly 180° (or half cycle) of the input signal; selective RF amplifiers can also be implemented using a single active element.
These amplifiers are subject to crossover distortion if the transition from one active element to the other is not perfect, as when two complementary transistors (i.e., one PNP, one NPN) are connected as two emitter followers with their base and emitter terminals in common, requiring the base voltage to slew across the region where both devices are turned off.[8]
Class AB
Here the two active elements conduct more than half of the time as a means to reduce the cross-over distortions of class B amplifiers. In the example of the complementary emitter followers a bias network allows for more or less quiescent current thus providing an operating point somewhere between class A and class B. Sometimes a figure is added (e.g., AB1 or AB2) for vacuum tube stages where the grid voltage is always negative with respect to the cathode (class AB1) or may be slightly positive (hence drawing grid current, adding more distortion, but giving slightly higher output power) on signal peaks (class AB2). Solid state class AB amplifier circuits are one of the most popular amplifier topologies used today.
Class C
Less than 50% of the input signal is used (conduction angle Θ < 180°). The advantage is potentially high efficiency, but a disadvantage is high distortion.
Class D
Main article: Switching amplifier
These use switching to achieve a very high power efficiency (more than 90% in modern designs). By allowing each output device to be either fully on or off, losses are minimized. The analog output is created by pulse-width modulation; i.e., the active element is switched on for shorter or longer intervals instead of modifying its resistance. There are more complicated switching schemes like sigma-delta modulation, to improve some performance aspects like lower distortions or better efficiency.
Additional classes
There are several other amplifier classes, although they are mainly variations of the previous classes. For example, class G and class H amplifiers are marked by variation of the supply rails (in discrete steps or in a continuous fashion, respectively) following the input signal. Wasted heat on the output devices can be reduced as excess voltage is kept to a minimum. The amplifier that is fed with these rails itself can be of any class. These kinds of amplifiers are more complex, and are mainly used for specialized applications, such as very high-power units. Also, class E and class F amplifiers are commonly described in literature for radio frequencies applications where efficiency of the traditional classes in are important, yet several aspects not covered elsewhere (e.g.: amplifiers often simply said to have a gain of x dB - so what power gain?) deviate substantially from their ideal values. These classes use harmonic tuning of their output networks to achieve higher efficiency and can be considered a subset of Class C due to their conduction angle characteristics.
Choices
- Quality
- Usage
- Need
- Demand
I needed an amp to power my woofer. The woofer is a 12” dual 2 ohm design and has a continuous rating of 750 watts total and the power delivered should not exceed 1500 watts or peak. I was also thinking about getting a second 12” woofer in the future, a total of 2 woofers but 4 voice coils. Which would lead to either a 2 ohm total load with both woofers or a 8 ohm load so for this I either needed an amp that could play well at 2 ohms mono or 4 ohms bridged. So I chose the amp that plays well at 4 ohms for the future or 2 ohms now. This amp required 2 4 gauge power wires and 2 4 gauge ground wires and a lot of amperage to run. Since this wasn’t the only amp I would be using and I was going to have other devices, go big.
With this decision comes a price, the price included buying gear. 100 farads of capacitance & 0 gauge wire to support the load in addition, various accessories and some studying up on the car I was gonna use. I had to upgrade the electrical under the hood, add circuit breakers and ensure I followed safety proto-calls to the letter. All this was to ensure:
- Fuel economy
- Life of the car & electronics
- Life of the equipment
- Clean awesome sound
This is explained best with this. I have speakers that will only need 50 watts of power to play at high volume when I call for it, most of the time the power to them at listening volume is about 20 watts per channel. I have front and rear speakers and am going to incorporate 3 way speakers in the front and the best way to power them is to “Bi-amp” them. This is to say that 2 channels will drive the mids and tweeters and 2 channels will drive the mid-bass drivers. So a 4 channel isn’t enough, so I used a 6 channel with about 55 watts per channel. This amp is perfect for my needs but a poor choice to run subs even though it has many channels and lots of clean pure sound.
When choosing an amp select it for the type that best fits the need matched with the class that best fits your need and pocketbook.
Their car many amps out there and a lot of good stuff, but most of it is crap. Sure this is my opinion, but it is backed up with experience and facts too.
To end this rant for now, I will say this. If you’re gonna brag about how much power you have or how cool your amp looks because it has dancing lights on it or its painted the same color as your car be ready to be circled. When I buy, I buy on the facts above and on if it will fit in my budget and car for that matter.
I have A/D/S for my 6 channels and Boston Acoustics for my sub. A/D/S has set the benchmark for high end home and car audio for 25 years and is widely coveted today by audiophiles around the world.
Later I will rant about speaker power output. Did you know 5 watts is really loud?
