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Old 11-22-2009, 01:55 PM   #1
Big Daddy Big Daddy is offline
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Default A Guide to Amplifiers

For a complete list of amplifier manufacturers, click HERE.

WHAT IS AN AMPLIFIER?

An amplifier’s main purpose is to take a weak signal and make it strong enough to drive a speaker. Amplifiers get the necessary energy for amplification of input signals from the AC wall outlet. If you had a perfect amplifier, all of the energy the amplifier took from the AC outlet would be converted to useful output to the speakers. However, no amplifier/receiver is 100% efficient, so some of the energy from the wall outlet is wasted in the form of heat.

COMPONENTS OF AN AMPLIFIER

Power Supply:
Amplifier/receivers need power supplies to convert the AC power from the wall to DC voltage. This conversion from AC to DC is necessary because the chips used inside the electronic equipment require DC voltage. Different types of power supplies are used in amplifiers. Some high quality amplifiers have independent power supplies for each channel.

A 4 ohm speaker is harder for an amplifier to drive than an 8 ohm speaker. The capabilities of an amplifier when driving low impedance loads is closely related to the capabilities of its power supply.

Input stage:
The purpose of the input stage (sometimes called the front end) is to receive the input signals for amplification by the output stage.

Output stage:
The output stage of an amplifier converts the weak input signal into a much more powerful signal to be sent to a speaker.

AMPLIFIER SPECIFICATIONS

Power Ratings:
Amplifiers are generally rated in watts per channel, at different impedances over a frequency range of usually 20 Hz - 20,000 Hz, at some amount of total harmonic distortion. Harmonic distortion increases with power output. Considerably more power can be delivered if distortion is allowed to increase.

Lower quality receivers/amplifiers sometimes have impressive power ratings like 1,000 watts, but if you examine the fine print, you will notice a total harmonic distortion level of 10% or so, and usually over a limited frequency range like 40-18,000Hz.

It is important to understand that two amplifiers that have the same power rating do not necessarily output the same power or sound alike. Also, power can not be amplified. Voltage and current can be amplified.

If you had a well-designed (perfect) amplifier and a perfect current source (wall outlet that had unlimited current availability), then each time you reduced the impedance by half, the power would be doubled. For example, an amplifier with a rating of 200 watts per channel at 8 ohms should be able to output 400 watts at 4 ohm and 800 watts at 2 ohm.

In the real world, amplifiers have real power supplies and their 4 ohm power rating is usually less than 100% more than the 8 ohm rating. Amplifiers with extremely good power supply will be able to do better, but eventually a limit will be reached as the AC outlet on the wall can only deliver so much current. As I said before, the capabilities of an amplifier when driving low impedance loads is closely related to the capabilities of its power supply.

Measures of Power

Power is not really something that can be amplified. Voltage and current can be amplified.

Calculation of RMS (Root Mean Squared) and Peak Power:
First, there is no such thing called RMS power. RMS refers to voltage, but erroneously people have gotten used to using it to rate power.

Power is defined as voltage squared divided by resistance.

P = V^2 / R

Let's assume we are dealing with a battery (DC voltage) and a resistor. If we apply 40 volts to an 8 ohm resistor, the voltage will always be the same (40 volts) so the power generated will always be the same. In this example, the power is equal to:

P = 40^2 / 8 = 200 watts

As a result of this power, the resistor will heat up to a certain temperature.

Now, let's change the voltage source to a 40 volt sine wave (AC current) and apply it to the same load resistor. In this case, the voltage is not constant and oscillates between +40 volts and -40 volts and as a result, the power generated will be less than 200 watts and the resistor will not get as hot.

How much sine wave voltage (AC) peak do we need to generate the same level of power and heat in the resistor as a DC voltage source?

The AC voltage required must have a higher peak than 40 volts DC to accomplish this. As it happens, the peak voltage is equal to the DC voltage, 40 volts, times the square root of 2. The detailed calculation of RMS Voltage requires some knowledge of calculus and is done HERE.

40 volts x sqrt(2) = 40 x 1.414 = 56.5 volts

Therefore, for a sine wave (AC) voltage source, we must apply 40 volts RMS to generate the same level of power and heat in the resistor.

In the above example, the RMS voltage of a pure sine wave of 40 volts is equal to 40 volts multiplied by the inverse of the square root of 2.





40 x 1/sqrt(2) = 40 x 1/1.414 = 40 x 0.707 = 28.3 RMS volts

or

The RMS voltage of a pure sine wave is approximately equal to peak voltage x 0.707.

The Following diagram should clarify the calculations above:



Diagram Created by Big Daddy


Continuous Power:
An additional factor that we must consider is the ability of the amplifier/receiver to output its full power continuously. In other words, just because an amplifier/receiver is listed as being able to output 100WPC, it does not mean that it can do so for any significant length of time.

You have to distinguish between peak power, RMS power, and continuous power. Many people wrongly assume that the RMS power rating is the same as a continuous power rating.

Remember that power is a snapshot of the amount of work being done at a given point in time. It does not have any specified time component attached to it.

For example, if we are applying a 40 volt sine wave voltage to a load resistance of 8 ohms, the peak power is calculated as:

Peak Power = 40^2 / 8 = 200 watts Peak

and

RMS power = 28.3^2 / 8 = 100 watts RMS

As you can see, the peak power rating is TWICE the RMS power output and is misleading.

RMS watts is better than peak power, but it can also be misleading as it contains no specified element of time. RMS wattage is a scientifically accurate way to measure power, but the amplifier may only be able to produce the RMS voltage into the given load for a fraction of a second.

Manufacturers that only report the RMS power rating may be trying to hide the truth. Although RMS voltage calculation is technically correct, it does not tell whether the amplifier is able to generate the stated RMS voltage for a continuous period of time. When they state continuous output power, they are saying that the amplifier can easily and continuously produce the rated output power.

The RMS continuous watts is a more honest way of reporting the power of an amplifier. However, it can also be deceptive as it is carried out at just one sine wave frequency at a time. This does not put a realistic demand on the amplifier compared to real life use. A better rating is the AES (Audio Engineering Society) rating, where the equipment being tested is subjected to a broadband pink noise signal. Pink noise signal contains equal energy in each octave frequency range. Testing using such a signal is more reliable when compared with a single frequency test (RMS) as it is testing over the whole frequency range at once.

The rated power output of an amplifier is understood to be its maximum output, it in no way means that the amplifier can only be used at this output. For example, if an amplifier is rated at 100 watts, the output can be anything between zero and this maximum rated value. Chances are that the amp can probably put out more if the input signal is over driven, however the quality of the output will degrade rapidly.

Amplifier Efficiency:
Efficiency is defined as the amount of output power divided by the amount of required input power. The maximum ideal efficiency that any circuit can have is 100%. In general, audio amplifiers are not very efficient. See efficiency of different classes of amplifiers in post #2 of this thread.

Dynamic Headroom:
Dynamic headroom is the ability of an amplifier/receiver to output power at a significantly higher level for short periods to accommodate musical peaks or extreme sound effects in movies. This specification is expressed in decibels. For example, a dynamic headroom of 3dB would indicate that an amplifier can double its output for a very short time to meet the above conditions.

It requires twice the power to increase the volume of a speaker by 3dB. The table below, for a speaker with sensitivity rating of 87db, shows how much you need to increase power to get an additional 3db increase in volume.



Table Created by Big Daddy


Read this article on Dynamic Headroom: http://www.axiomaudio.com/dynamicheadroom.html


Clipping:
Clipping occurs when one tries to get a larger output signal out of an amplifier than it was designed to provide.

This is a normal sine wave:



This is a clipped sign wave:



Amplifier clipping occurs when the the signal level is exceeding the maximum capability of the amplifier. Graphically, this means that the tops of the audio signal are “clipped off” or become flat. Clipping is the enemy of speaker drivers, particularly the high frequency drivers.

During the times when a signal from the amplifier is clipped, the cones of the speaker drivers are not instructed to move in and out. It is as if they are receiving a DC signal. This means that all the amplifier's power goes into heating the voice coils instead of producing sound.

Unfortunately, the more efficient the drivers are in converting power to sound, the worst the problem becomes. High frequency drivers (tweeters and mid-range drivers) are normally more efficient than low frequency drivers in converting power to sound. During clipping all that power will be completely converted to heat. High frequency drivers do not have the mass to tolerate the excess heat and are more likely to fail.

Signal-To-Noise Ratio (S/N):
All amplifiers and all electrical circuits generate a certain amount of electrical noise. Amplifiers that are designed better minimize the amount of noise. However, no matter how good the design, there will always be some noise. Generally, the more powerful the amplifier, the more noise it will produce. An amplifier with a poorly regulated power supply can create additional noise.

The Signal-To-Noise Ratio (S/N) measures the ratio of sound to background noise. It is expressed in decibels. S/N is calculated by measuring a unit's output noise, with no signal present, and all controls set to a predetermined level. A higher number is desirable.

Distortion:
Distortion in an amplifier is the alteration of the original shape (or other characteristic) of the signal. Distortion is usually unwanted. All amplifiers alter input signals, generally in two ways: they make them stronger (amplify) them, and they add characteristics which did not exist in the original signal. These undesirable characteristics are called distortion.

Harmonic Distortion:
Harmonic distortion is one of the most common type of amplifier distortion. Harmonics of a signal are signals which are related to the original (or fundamental) by an integer (non decimal) number. Music is made of fundamental frequencies and their harmonics. For example, the note "A" (2nd string from the right on the violin, or "A" above middle "C" on the piano) consists of a fundamental frequency of 440Hz. It is also reproducing harmonics of that frequency such as 880Hz (440 x 2), 1220Hz (440 x 3) , 1760Hz (440 x 4), and so on. The volume of each harmonic frequency is lower than the fundamental frequency. Note A of other musical instruments sounds different because of their fundamental frequencies and their harmonics.

A pure tone signal has no harmonics; it consists of only one single frequency. If a pure tone signal was applied to the input of an amplifier, we would find that the output of the amplifier is not pure and consists of the an amplified version of the input signal plus distortion created by the amplifier. All amplifiers and signal processors add distortion to the signal.

Total Harmonic Distortion, or THD is specification that compares the output signal of the amplifier with the input signal and measures the level differences in harmonic frequencies between the two. The difference is called total harmonic distortion. The levels of harmonic distortion in most high quality amplifiers are very small and below audibility. It is generally accepted that a THD below 1% is not audible.

Do two amplifiers with identical THD ratings sound the same, everything else being equal? Not necessarily, but differences will be subtle and difficult to hear.

Calculation of Total Harmonic Distortion:
THD is a measurement of the total number of harmonics that are in addition to the fundamental harmonic being measured and are expressed as a percentage of the fundamental frequency. To measure THD, a reference frequency must be specified (the fundamental) and any remaining frequencies measured. For example, a test tone of 1kHz may be applied to the amplifier. The THD analyzer is designed to ignore the fundamental (in this case 1kHz) and measure anything else remaining. This is done by summing together all remaining frequencies at the output of the amplifier under test ignoring the 100% 1kHz test tone.

There are two equations for calculating THD. The first one requires calculating the power of each harmonic frequency.

THD = 100 * SQRT[(P2 + P3 + P4 + ... + Pn) * R] / Vrms

where

THD = total harmonic distortion in percentage
Pi = the power of each harmonic
R = the load (output) impedance
Vrms = total RMS output voltage (containing both the fundamental and the harmonic terms)

Another way of getting the same answer would be to take the square root of the sum of the squares of harmonic voltages.

THD = 100 * SQRT[(V2)^2 + (V3)^2 + (V4)^2 + ... + (Vn)^2] / Vrms

where

THD = total harmonic distortion in percentage
Vi = the RMS voltage of each harmonic
Vrms = total RMS output voltage (containing both the fundamental and the harmonic terms)

TDH(%) is total harmonic distortion, V represents the RMS voltage of each harmonic, and Vt is the total RMS output voltage.
Note that Zout is not present in this variant of the equation;
since P = V2/Z, the impedance terms cancel.

Example: Let us assume that we use a sine-wave generator to input a certain frequency wave at the input of an amplifier, and adjust it so that it outputs 20 volts RMS into an 8-ohm load. Assume the second harmonic is measured at 0.5 volts RMS, the third harmonic at 0.4 volts RMS, and the 4th harmonic at 0.3 volts RMS. For the sake of simplicity, we assume that the rest of the harmonics are too small and can be ignored.

We can use the above formulas to calculate the THD. The results are summarized in the following tables:



Table Created by Big Daddy



Table Created by Big Daddy


Intermodulation distortion:
Inter-modulation Distortion measures non-harmonic frequencies added to the signal. This type of distortion is the result of two or more signals mixing together that are not harmonic frequencies and are undesirable. For example, if an amplifier creates a non-harmonic frequency of 300Hz along with the fundamental frequency of 440Hz (C note for violin), a third frequency of 740Hz (440 + 300) and a fourth frequency of 140Hz (440-200) will also be produced. These new frequencies are not harmonics of 440Hz. Thus, it is termed intermodulation distortion because it is between harmonic frequencies.

Intermodulation distortion is much more objectionable to the human ear than harmonic distortion.

Input Sensitivity of an Amplifier:
A pre-amplifier has two basic functions:

1. Allow input switching.
2. To achieve synergy between the source(s) and the amplifier(s).

Input switching is well understood by most users and is rather elementary. The second function is not quite as easy for most users to understand. To select an appropriate preamp, you must know two things:

1. The output voltage of the source. Most CD players, for example, have an output voltage of 2 volts.
2. The input sensitivity of the amplifier. Most amplifiers have an input sensitivity of around 1 volt.

Output Voltage: The output voltage of the source is normally a constant level unless the source has a variable output knob. This output voltage (e.g., 2 volts of CD music) drives the input stage of the preamp which in turn drives the input stage of the amplifier.

Input Sensitivity: The input sensitivity of an amplifier is defined as how many volts are required to bring the amplifier to full power. Any amount of voltage beyond that number will force the amplifier to try to output more power than it is capable of and therefore results in clipping.

So we can conclude that an important job of the preamp is to control the voltage from the source to the amplifier. This is done by adjusting the volume control. When the preamp volume is all the way down, the output signal is attenuated completely to zero volts and no sound. As the volume knob is turned up, the voltage increases as does the sound generated from the amplifier. Assuming the output voltage of the source is more than the input sensitivity of the amplifier, the ideal working range on a volume control should be where the preamp would not add any voltage gain to its input signal beyond the amplifier’s input sensitivity.

When do we need gain in a preamp?

When the input sensitivity of the amplifier is above the output voltage of the source. It is possible for some amplifiers to need up to 5 volts to bring them to full power. On the other hand, it is possible for some to only need 1/2 volt to come to full power. It is also possible for some modified CD players or Digital/Analog Converters to have less then 2 volts.

As an example, assume an amplifier with an input sensitivity of 2 volts is connected to a source with an output voltage of 1 volts. We will definitely need a preamp with some gain. Otherwise, it will not be possible to play the amplifier as loud as it it is capable of. Even if the speakers are very efficient, the music will lack dynamics and weight at low listening levels. Turntables have very low output sensitivity. That is the main reason why you need a built-in or external phono stage with turntables,


Example: Let’s say we have an 8-ohm loudspeaker that has a sensitivity of 87dB for one watt at one meter. Assume we are trying to achieve a desired maximum peak sound pressure level of 105dB. If the signal source has an output voltage of 1 volt, how much amplifier gain is required?

Remember that in order to increase the level of sound by 3dB, we need to double the amplifier’s power.

SPL, Watts
87dB, 1
90dB, 2
93dB, 4
96dB, 8
99dB, 16
102dB, 32
105dB, 64

Therefore, we need 64 watts to achieve a peak SPL of 105dB. From Ohm’s law,

Power = V^2 / R

64 = V^2 / 8, and V = 23 volts

So the amplifier needs to provide a voltage gain of 23 times which is approximately 27dBv. Please note that 0 dBv is defined as Vo = 1 volt, and

dBv = 20 . LOG(V/Vo) = 20 x LOG(23/1) = 27 dBv.

Some amplifiers have knobs that control the amplifier’s input sensitivity. When the knob is turned clockwise, the sensitivity will increase. Turning the control counter-clockwise will decrease sensitivity. This control is not a volume control for the amplifier. The amplifier can be driven to full power with a wide range of signal levels. A low level signal will require increased sensitivity for full power. A high level signal will require decreased sensitivity.

The other issue that we need to consider is output impedance of preamps and input impedance of amplifiers.

Output Impedance: All sources and preamps have output impedance. Output impedance is defined as the ability of a unit to drive difficult loads.

Input Impedance: Amplifiers, preamps and receivers have input impedance. Think of it as the difficulty the amplifier imposes on the preamp and the preamp (receiver) imposes on the source.

Generally speaking, we can make the following conclusions:
  1. The lower the output impedance of the preamp, the better it will drive difficult loads.
  2. The higher the input impedance of the amplifier, the less difficult it will for the preamp to drive it.
For example, a preamp with an output impedance of 1,000 ohms can easily drive an amplifier with an input impedance of 100,000 ohms.

Most stock (unmodified) CD players have a relatively low output impedance. Unfortunately, amplifiers' input impedances vary quite a bit. Although the most common number is 50,000 ohms, they can vary between 10,000 ohms and 500,000 ohms.

Although 50,000 ohm is a load that most sources and preamps can drive easily, you may run into difficulty if you use extra long interconnects to connect a preamp with very high output impedance to a 50,000 ohm amplifier. The result may be either reduction in bass response, or lack of dynamics, or both. This is sometimes described as thin sound. The solution is to reduce the length of the interconnects and/or use a preamp with low output impedance.

The Slew Rate:

The slew rate in electronics is the maximum rate at which an electronic amplifier can respond to a sudden change in input level. The term is used to define the maximum rate of change of an amplifier's output voltage with respect to its input voltage. The unit of measure is volts per microsecond. A slew rate of 1V/s, for example, means that within 1 microsecond, the amplifier can go from 0 to 1 volt. The slew rate in amplifiers is similar to acceleration in cars. This is important because it defines the maximum speed at which an amplifier can handle a transient waveform. The higher the slew rate, the faster is the amplifier.

Measurement
The slew rate can be measured using a function generator (usually square wave) and oscilloscope. Slew rate is measured by feeding an input signal that is too fast for the amplifier to cope with. It is the time an amplifier needs to go from 10% to 90% of the total output voltage in response to a step in voltage at the input. Slew rate is an overload condition, and it should not happen at all for an audio amplifier. Therefore, being concerned about the slew rate is meaningless.

This specification limits the capability of an amplifier to generate high voltage pulses with sharp rising and falling edges. This is exhibited in Figures 2, 3, and 4.




The higher the frequency, the faster the voltage has to rise to prevent distortion of the sine wave. If the amplifier cannot follow due to its limited slew rate, the sine wave will be distorted and its amplitude is lower than at low frequencies. Limitations in slew rate can result to non linear effects. For a sinusoidal waveform not to be subject to slew rate limitation, the slew rate capability at all points in an amplifier must satisfy the following condition:

SR >= 2Pi x f x Vpk

where f is the frequency and Vpk is the peak amplitude of the waveform.


Continued in the next post.


CONCLUSIONS

When buying an amplifier/receiver, it is important to look at the following factors:
  • Distortion: Total Harmonic Distortion (THD) and Intermodulation Distortion (IMD), lower numbers are better.
  • Signal-To-Noise (S/N) Ratio: The higher number is better.
  • Continuous Power: Just because the receiver/amplifier may be listed as being able to output 100WPC, doesn't mean it can do so for any significant length of time. Always make sure the watt per channel is in continuous RMS terms. Even RMS power is technically incorrect. RMS voltage is normally measured.
  • Dynamic Headroom: The ability of the receiver/amplifier to output power at a significantly higher level for short period of time to accommodate musical peaks or extreme sound effects in movies. Dynamic Headroom is measured in Decibels. If a receiver/amplifier has the ability to double its power output for a brief period, it would have a Dynamic Headroom of 3db.
  • Impedance Rating: Almost all receivers can handle 8 ohm speakers. Some can handle 6 ohm speakers. Almost none of them can handle 4 ohm speakers. Using a receiver on a low impedance speaker will result in overheating and possible damage to the receiver and/or the speaker.
  • Other Options: You should look at the other options that the receiver offers, such as the number of HDMI input/outputs, the kind of video processing, DSP modes, etc.
REFERENCES AND ADDITIONAL INFORMATION

Home Theater: To Separate or Not to Separate?
audioport.com
Power Amplifier Fundamental
Power Amplifier Power Specs Demystified
http://www.harmanaudio.com/all_about...werratings.asp
http://www.usedphones.com/Amplifiers.html
http://www.hometheatersound.com/feat...c_20010901.htm
http://sound.westhost.com/bi-amp.htm
http://sound.westhost.com/tweeters.htm
http://www.audioholics.com/education...r-voltage-gain
Amplifier Power Ratings
Distortion - Wikipedia, the free encyclopedia
Total harmonic distortion - Wikipedia, the free encyclopedia
THD Measurement and Conversion
What is Total Harmonic Distortion? - THD - Definition and Explanation of THD
What is Intermodulation Distortion? - IMD - Definition and Explanation of IMD
How Much Amplifier Power Do You Really Need? - Amplifier Power - What You Need To Know About Amplifiers and Amplification
Total Harmonic Distortion
PS Audio - High-Performance Home Audio Equipment
http://www.analog.com/en/content/0,2..._91250,00.html
Audio Specifications
3 ways of expressing voltage of a common AC wave form
Measurements of AC magnitude - Basic AC Theory
What is Alternating Current?
RMS Calculator
http://www.eznec.com/Amateur/RMS_Power.pdf
Sound & Communications - Audio
http://www.1388.com/articles/tech_underAmp
Deutsches Institut fr Normung : Startseite DE
Amp Input Sensitivity and Gain
Setting Sound System Level Controls
Pro Audio Reference D
DECWARE - Audio Paper - How to choose the right preamp
http://en.wikipedia.org/wiki/Slew_rate
http://www.falco-systems.com/high_vo...mplifiers.html
http://www.sweetwater.com/shop/live-...ying-guide.php
http://www.psaudio.com/ps/wiki/Slew-Rate/

Last edited by Big Daddy; 05-07-2013 at 06:26 AM.
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Old 11-22-2009, 01:55 PM   #2
Big Daddy Big Daddy is offline
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You can find additional information on Input Sensitivity in THIS POST.

DAMPING FACTOR

Why Do We Need Damping?
Without any type of damping, when the signal to a loudspeaker stops, it keeps on vibrating due to inertia. This is called ringing or overhang. In other words, the speaker produces sound waves that are not part of the original signal. The frequency of the sound that the speaker produces with this movement will be at the resonant frequency of the moving system. As an example, suppose the incoming signal is a short and precise sound from a kick-drum. When the kick-drum signal stops, the speaker’s cone continues to vibrate back and forth in its suspension and the sharp sound from the kick drum turns into a boomy rhythm.

What is Damping?
Damping is the term used in reducing the sound produced by a loudspeaker’s moving diaphragm after the signal stops.

Types of Loudspeaker Damping
There are two types of loudspeaker damping: mechanical and electrical. The loudspeaker's suspension and its quality determine the amount of mechanical damping. Manufacturer’s try to use sophisticated techniques to improve the mechanical damping of their loudspeakers.

Electrical Damping Factor
Electrical damping is provided by the receiver/amplifier. Electrical damping is the ability of a receiver/amplifier to control a loudspeaker’s motion after the signal has stopped. The higher the damping factor, the better the receiver/amplifier will control the loudspeaker and help reduce overhang distortion.

How Does Electrical Damping Work?
When a loudspeaker’s cone vibrates in a magnetic field, it generates a signal like a microphone. This signal will have an opposite polarity and is called Electro Motive Force (EMF). It travels back through the speaker wire to the receiver/amplifier’s output and it is send back again to the speaker. Because of its opposite polarity, it will damp or impede the loudspeaker’s overhang. The smaller the receiver/amplifier's output impedance, the greater will be the effect of back EMF on the loudspeaker's motion.

As you can see, it is not the amplifier that controls the loudspeaker. The loudspeaker damps itself through the output circuitry of the receiver/amplifier. The lower the output impedance of the receiver/amplifier, the larger will be the effect of the back EMF on the loudspeaker’s overhang or ringing.

A Practical Experiment to Understand Back EMF
Take a woofer that is not connected to anything and put your ear next to the cone of the woofer. Now tap on it with your fingers. You will hear a low-pitched thump sound. Repeat the experiment, but this time short the speaker terminals with a pair of wires attached to the loudspeaker’s terminals. Because of back EMF, you should hear a much tighter thump sound.

Calculation of Damping Factor (DF)
The Electrical Damping Factor (DF) coefficient is determined by dividing the loudspeaker’s load impedance by the source impedance of the receiver/amplifier.

Electrical Damping Factor = Load Impedance / Source Impedance

A typical receiver/amplifier’s source impedance is 0.02 Ohms. If the load impedance of the loudspeaker is 8 ohms, then the damping factor can be calculated as follows:

DF = 8 / .02 = 400

If the loudspeaker’s impedance drops to 4 Ohms, the electrical damping factor will also drop:

DF = 4 / .02 = 200

The damping factor is the ability of the receiver/amplifier to control the loudspeaker’s load. The impedance of the load and the impedance of the output (source) affect the receiver/amplifier's ability to control its load.

High damping factor usually means that the bass response will be well defined and tight, whereas a low damping factor will result in a loose sounding bass. Tube amplifiers generally have lower damping factors compared to solid state amplifiers. This may contribute to their typically loose bass response, which may be very pleasant and many audiophiles describe as warm. Because the electrical damping is minimal, it is a good guarantee that you are hearing what the loudspeaker’s designer has created.

Size of the Loudspeaker’s Driver
Electrical damping becomes more important as the size of the loudspeaker’s driver becomes larger. Subwoofers have the most problems regarding damping. Their moving mass is quite high and their suspensions are relatively weak compared to their size. Because of this they have relatively weaker mechanical damping and therefore electrical damping becomes more important. In severe cases, if proper damping is not used, the moving mass of the subwoofer creates a one note bass. High frequency drivers have much lighter mass, stiffer suspensions, and stronger mechanical damping. As a result, electrical damping becomes relatively less important.

Effect of Speaker Wires
The electrical damping factor is also affected by the resistance of the speaker wires. Speaker wires like most electronic devices have resistance that oppose the flow of current. The thinner the wire and the longer the length of the wire, the larger will be the resistance of the speaker wire. Therefore, we need to slighly modify the electrical damping formula to account for the effect of speaker wires. The modified formula is as follows:

Damping Factor = Load Impedance / (Source Impedance + Cable Impedance)

Conclusion
Like most other specifications, damping factor by itself does not tell you that a receiver/amplifier is good. There is a lot more to designing a good receiver/amplifier besides output impedance and damping factor. A very high damping factor usually means that the receiver/amplifier has very low output impedance, and many people worry that because of high negative feedback, such a receiver/amplifier may distort the sound. It is widely accepted that the damping factor should be around 20 or higher. A damping factor below 20 does change the performance of the loudspeaker (for better or for worse, depending upon the speaker). But it is hard to prove that a damping factor of 300 is better than 20.


WHY DO I HEAR A "THUMP" WHEN I TURN OFF MY AMPLIFIER?

The job of a power supply in an amplifier is to filter and store energy until the amplifier circuitry needs it. Normally, this energy is stored in capacitors. When you turn the amplifier off, that energy has to go somewhere. The thump that you hear when the amp is turned off is the power supply capacitors discharging the energy. It is not usually dangerous and doesn't hurt anything.

Some amplifiers make a "whooshing" sound when you turn them on. The noise is not exactly what is considered to be a "thump" but it is noises that sometimes have high and low frequencies together. It is more like a "thump" mixed with a "pefffft".

It is a good idea not to plug an amplifier or subwoofer amplifier to the back of the receiver. In most cases, plug them directly into the wall outlet. Also, when you turn on and turn off the equipment, do that sequentially and wait a few seconds after each step and give the component time to reach steady state.

Some DIY people or people in car audio use output relays that would disconnect the speakers as soon as the amp turned off. That way, you would never hear the thump. But relays generally degrade the sound and people in hi fidelity don't recommend them.

Leaving an amplifier on most of the time may do less damage to the amplifier than regularly turning it on and off. The power usage is minimal. Leave it on and only turn it off when you are going to be absent for an extended period.


CONNECTING MULTIPLE SPEAKERS TO A SINGLE AMPLIFIER

When two or more speakers are connected to the same amplifier, then impedance becomes a major concern. For example, if the two 8 ohm speakers are connected in parallel, the impedance will drop to 4 ohms. If they are connected in series, the impedance will rise to 16 ohms. When the impedance drops, more current will flow into the speakers. When the impedance rises, the current going to the speakers will drop.

Amplifiers With A/B Switch:
Some amplifiers have connectors for two pairs of speakers and have an A/B switch on the front panel. Most of these amplifiers connect speakers in parallel when both speakers are selected. It is common for these amplifiers to require 8 ohm speakers only, because they are usually built to drive either 4 or 8 ohms, and two sets of 8 ohm speakers in parallel will result in 4 ohms. If you connect two set of 6 ohm or 4 ohm speakers to these type of amplifier, they may overheat and fail.


CONNECTING MULTIPLE AMPLIFIERS TO A SINGLE SPEAKER

You can add two amplifiers to the same speaker in two different ways:
  1. Bridging

    Bridging an amplifier is a procedure to generate more output voltage by inverting the second channel (or the second mono amplifier) and connecting it to one speaker. Think of it as connecting two mono channels in series. The impedance implication will be the opposite of series speakers. In the case of series speakers, the impedance will rise. When you bridge two channels of an amplifier, you will be cutting the effective load impedance in half. For example, if a bridged amplifier is connected to a 4 ohm speaker, it will make the effective impedance 2 ohms. This is why an amplifier can quadruple the rated power of a single channel when bridged. Many people believe that if their amplifier is stable for 4 ohm loads, then they can bridge it to a 4 ohm speaker load. This is not the case as a bridged amplifier will see the 4 ohm speaker as a 2 ohm speaker load and the amplifier may fail. I did this recently and damaged my amplifier.

    A two channel amp can be bridged to one channel, and a four channel amp into two channels. Bridging the channels increases the power output. An amplifier is usually bridged to combine two channels to power one speaker/subwoofer, or to combine four channels into powering two speakers/subwoofers.

    It is common to bridge the power amplifier to increase the power available and generate more output from the sound system. This may be appropriate with a passive subwoofer. However, if you are dealing with full range speakers, it may be more appropriate to bi-amp them.

    Bridgeable amplifiers are designed with an inverted channel for bridging purposes. The inverted channel produces voltage that is generated at the opposite polarity of the un-bridged channel.

    Sometimes your amp will have a diagram for bridging. For example, look at the far right of the following 4-channel amplifier for bridging diagram.




    If your amp is not able to bridge, you may still be able to do it with a DIY bridging adapter, but Before you attempt to bridge an amplifier, there are certain things you must keep in mind. Only bridge an amplifier that can handle the increased power load. Do not bridge an amp that will be unstable at the bridged load.

    To understand how to bridge an amplifier that is not bridgeable, read these articles.


    Simplest Ever Bridging Adapter for Amplifiers
    Bridging Adapter For Power Amps
    Yamaha Corporation of America - FAQDetail







    Bridging an amplifier produces twice the voltage and four times the power as it would in an un-bridged status. As an example, consider a 200 Watt per channel amplifier into 8 Ohms. This amplifier requires a signal voltage of 40 Volts RMS per channel to generate 200 watts per channel:

    P = V^2 / R = (40)^2 / 8 = 400 / 8 = 200 Watts

    The same amplifier into 4 Ohms will deliver close to 400 watts, provided the power supply can remain stable under the load.

    If the two-channel amplifier is bridged into a single channel, the 8 Ohm loudspeaker now sees double the voltage. Using the formula above, we get:

    P = V^2 / R = (80)^2 / 8 = 1600 / 8 = 800 Watts

    ------------------------------------------------------------------------------------------------------------------
  2. Connecting Two Mono Amplifiers to the Same Speaker.

    When two amplifiers are connected in parallel, the effect on impedance will be the opposite of parallel speakers. If you connect two speakers in parallel, the impedance will drop. With parallel amplifiers, the impedance will rise. For example, if two identical amplifiers, each rated for 4 ohms, are connected to a 4 ohm speaker, each amplifier will see an equivalent of 8 ohm and each amplifier will supply half the current that it provided before. With this type of setup, the two amplifiers must be identical because they see each other as loads. If the amplifiers are different, the stronger one will try to drive the other one and you run into all sorts of problem. Furthermore, the gains for the two amplifiers must be exactly the same.

AMPLIFIER CLASSES

You can find a very good discussion of amplifier classes with advantages and disadvantages in http://en.wikipedia.org/wiki/Electronic_amplifier.

http://nobleamps.com/ampclasses.html
Quote:
What is Bias?
In electrical terms, a circuit’s bias is where it will settle when there is no input signal. This point is also referred to as “idle” or “quiescent”. It may help to think of a tube as a valve or water faucet - in class B the faucet would turn all the way off when not in use, in class A the faucet would run at half its maximum flow when not in use, and in class AB it would drip, or slowly trickle.
http://www.yourdictionary.com/comput...lifier-classes
http://www.pcmag.com/encyclopedia_te...i=55350,00.asp
Quote:
Analog amplifiers are categorized by how much current flows during each wave cycle. Measured in degrees, 360º means current flows 100% of the time. The more current, the more inefficient and the more heat generated.

ANALOG

Class A
The amplifier conducts current throughout the entire cycle (360º). The Class A design is the most inefficient and is used in low-power applications as well as in very high-end stereo. Such devices may be as little as 15% efficient, with 85% of the energy wasted as heat.

Class B
The current flows only 180º for half the cycle, or two transistors can be used in a push-pull fashion, each one operating for 180º. More efficient than Class A, it is typically used in low-end products.

Class AB
Combines Class A and B and current flows for 180º to 200º. Class AB designs are the most widely used for audio applications. Class AB amplifiers are typically about 50% efficient.

Class C
Operating for less than half of one wave cycle (100º to 150º), Class C amplifiers are the most efficient, but not used for audio applications because of their excessive distortion.

Class G
A variation of the Class AB design that improves efficiency by switching to different fixed voltages as the signal approaches them.

Class H
An enhancement of the Class G amplifier in which the power supply voltage is modulated and always slightly higher than the input signal.




Current Flowing

The red indicates how much of the time current is flowing through one wave cycle.


DIGITAL

An audio amplifier that works in the digital domain. It generates the equivalent analog output for the speakers by using pulse width modulation (PWM) or pulse density modulation (PDM) rather than the traditional digital-to-analog conversion.

Less Heat than Analog
Because pulse modulation output signals are either on or off, Class D amplifiers produce far less heat than analog amplifiers. Reaching efficiencies greater than 90% compared to only 50% for analog, they are widely used for every amplification requirement from cellphone speakers to high-end stereos.

Digital and Analog
Class D was not coined for "digital;" it was the next letter after Class C. However, it does produce a "digital-like" output because the signals are generated by turning a switch fully on or off. But it is not technically digital because the output is not digital data. It is a modulated audio signal that is feeding analog speakers and is equivalent to the output of a traditional analog amplifier. Some call this a "synthesized analog" output.

Class D
Class D is a digital-like amplifier that works by turning a transistor fully on or off, but the "D" technically does not stand for digital.

Class T
A variation of the Class D technique from Tripath. Class T modulates the pulses based on the individual characteristics of the output transistors.
http://www.ultimate-guitar.com/colum...r_classes.html
Quote:
Classes are not grades of quality; they are classifications based off how they work.

In essence, an amplifier’s class is based upon how much of the original signal is used through the circuit. More often than not, the percentage used is notated as an angular degree, or the “angle of flow”. Therefore, = 360 means that the full signal is used, and = 180 would be half of the signal. The angle of flow is also closely related to the efficiency of the amplifier. Let’s take a look at each individual class:

Class A
In this form of amplifier, 100% ( = 360) of the original signal is used throughout the whole circuit. The result is an upscale version of the original signal, unclipped and effectively amplified to a more intense, usable signal. These amplifiers are very energy inefficient however; because the amplifying element is biased to constantly be conductive, power is drawn from the source even when no signal is being input. In layman’s terms, the amplifier is drawing power even when you’re not playing.

Up to one Watt is dissipated for every Watt used to amplify the signal. This 1:1 ratio means that as much energy is wasted as is used when managing the linear signal. To many players, this inefficiency is worth it; the main reason for a Class A’s linear signal function is the use of tubes. Tubes have asymmetrical output, resulting in even and odd-numbered harmonics. While this is chalked up to opinion, many players agree that tubes producing those forms of complex harmonics result in a higher-quality sound.

Class B
In these amplifiers, only half of the signal ( = 180) is used, resulting in a lot more clipping (distortion) but a more efficient system. The system only operated half the time, processing half of the signal, so it naturally uses less power. It is unusual, however, to find amplifiers using single Class B elements due to unusual output signal, and are more often found in personal radios and battery-operated devices than . Instead, they are quite often paired with with a matching push-pull element, resulting in a Class AB system.

Class AB
Relying on the use of two Class B units, a Class AB system is a pair of complementary push-pull devices, each amplifying ~55% ( = 198) of the original signal and combining them afterwards, resulting in a full signal. The reason why each device takes more than 50% of the signal is to ensure that the signals crossover and match up, and no device is completely shut off at any time. However, Class AB amplifiers are still extremely efficient. There is the risk of crossover distortion, where the mismatched signal ends clip once combined; at most performance volumes, the distortion is not easily noticed and a the power efficiency of the amplifier is considered to be worth it.

Class C
Class C amplifiers conduct less than 50% of the original signal. This results in an unusually high level of sound clipping and signal distortion. Class C amplifiers are extremely efficient, boasting up to about 90% efficiency. However, they are more complex than normal amplifiers and are not usually found in guitar amplification systems, but instead have vocal and other instrumental practicality. A Class C amplifier has both a “tuned”, or “clamped” mode of operation, and an “untuned” mode. When tuned, the amplifier is biased so that only one-half of the input voltage is utilized, resulting in less power dissipated and wasted after amplification. Again, in layman’s terms, only half of the signal is input, but it retains its form after processing. It is possible to bias the amplifier to end up producing a signal that is reactive to very specific harmonics, for instruments such as bells or tuned idiophones.

Class D
These amplifiers operate similarly to Class AB units, running two separate signals (~ = 198), but instead use switches at each transistor that can turn on and off when there is no signal input. The result is a moderately clean signal that is amplified using very little power. This class is usually only found in batter-powered mini-amps which rely on weak power sources and need as much life longevity as possible.

Class G and Class H
Most players will never play through these types of amplifiers, yet they are quite unique. Usually used for high-volume performing such as in a stadium or other large venue, these amplifiers have the ability to run off multiple voltages. A series of power supply rails with adjustable voltages run along the signal, allowing a different voltage to be used depending how far through the device the signal is. The advantage to adjustable voltages is a very low (almost 0%) amount of wasted power at the output transistors or after the signal passes through the tubes. These classes of amplifiers are usually costly enough that any less of an efficient design wouldn’t be worth the price.

So there’s a basic explanation of power amplification. Hopefully this clears up a little misunderstanding about amplifier quality and classes. Depending on your situation, buying an amplifier of a specific class can be very beneficial. Next time you try out some amplifiers, ask to try a few different classes and get a feel for each; you may end up liking a new sound.

By Kevin Heiland
http://www.audioc.com/library1/glossary.htm
Quote:
Amplifier classes: Audio power amplifiers are classified primarily by the design of the output stage. Classification is based on the amount of time the output devices operate during each cycle of signal swing. Also defined in terms of output bias current, (the amount of current flowing in the output devices with no signal).
  • Class A operation is where both devices conduct continuously for the entire cycle of signal swing, or the bias current flows in the output devices at all times. The key ingredient of class A operation is that both devices are always on. There is no condition where one or the other is turned off. Because of this, class A amplifiers are single-ended designs with only one type polarity output devices. Class A is the most inefficient of all power amplifier designs, averaging only around 20%. Because of this, class A amplifiers are large, heavy and run very hot. All this is due to the amplifier constantly operating at full power.The positive effect of all this is that class A designs are inherently the most linear, with the least amount of distortion.

  • Class B operation is the opposite of class A. Both output devices are never allowed to be on at the same time, or the bias is set so that current flow in a specific output device is zero when not stimulated with an input signal, i.e., the current in a specific output flows for one half cycle. Thus each output device is on for exactly one half of a complete sinusoidal signal cycle. Due to this operation, class B designs show high efficiency but poor linearity around the crossover region. This is due to the time it takes to turn one device off and the other device on, which translates into extreme crossover distortion. Thus restricting class B designs to power consumption critical applications, e.g., battery operated equipment, such as 2-way radio and other communications audio.

  • Class AB operation allows both devices to be on at the same time (like in class A), but just barely. The output bias is set so that current flows in a specific output device appreciably more than a half cycle but less than the entire cycle. That is, only a small amount of current is allowed to flow through both devices, unlike the complete load current of class A designs, but enough to keep each device operating so they respond instantly to input voltage demands. Thus the inherent non-linearity of class B designs is eliminated, without the gross inefficiencies of the class A design. It is this combination of good efficiency (around 50%) with excellent linearity that makes class AB the most popular audio amplifier design.

  • Class AB plus B design involves two pairs of output devices: one pair operates class AB while the other (slave) pair operates class B.

  • Class D operation is switching, hence the term switching power amplifier. Here the output devices are rapidly switched on and off at least twice for each cycle. Since the output devices are either completely on or completely off they do not theoretically dissipate any power. Consequently class D operation is theoretically 100% efficient, but this requires zero on-impedance switches with infinitely fast switching times -- a product we're still waiting for; meanwhile designs do exist with true efficiencies approaching 90%.

  • Class G operation involves changing the power supply voltage from a lower level to a higher level when larger output swings are required. There have been several ways to do this. The simplest involves a single class AB output stage that is connected to two power supply rails by a diode, or a transistor switch. The design is such that for most musical program material, the output stage is connected to the lower supply voltage, and automatically switches to the higher rails for large signal peaks. Another approach uses two class AB output stages, each connected to a different power supply voltage, with the magnitude of the input signal determining the signal path. Using two power supplies improves efficiency enough to allow significantly more power for a given size and weight. Class G is becoming common for pro audio designs.

  • Class H operation takes the class G design one step further and actually modulates the higher power supply voltage by the input signal. This allows the power supply to track the audio input and provide just enough voltage for optimum operation of the output devices. The efficiency of class H is comparable to class G designs.


How much power do I need?
Quote:
According to JBL Pro:
Ideally you should pick an amplifier that can deliver power equal to twice the speaker's continuous power rating. This means that a speaker with a "nominal impedance" of 8 ohms and a continuous power rating of 350 watts will require an amplifier that can produce 700 watts into an 8 ohm load. For a stereo pair of speakers, the amplifier should be rated at 700 watts per channel into 8 ohms.

A quality professional loudspeaker can handle transient peaks in excess of its rated power if the amplifier can deliver those peaks without distortion. Using an amp with some extra "headroom" will help assure that only clean, undistorted power gets to your speakers.
http://www.jblpro.com/pages/general_faq.htm
http://www.jblpro.com/pub/technote/lowpower.pdf


REFERENCES AND ADDITIONAL INFORMATION

Digital Vs. Analog Amplifiers:
http://www.canadahifi.com/digitalamps.php

http://nobleamps.com/ampclasses.html
http://forums.afterdawn.com/thread_view.cfm/79383
http://www.zedaudiocorp.com/Technica...er-Classes.htm
http://www.wordiq.com/definition/Electronic_amplifier
http://www.crownaudio.com/pdf/amps/137234.pdf
http://www.duncanamps.com/technical/ampclasses.html
http://www.tpub.com/neets/book7/25e.htm
http://en.wikipedia.org/wiki/Electronic_amplifier
http://www.bcae1.com/ampclass.htm
http://www.calvin.edu/~pribeiro/cour...a-chapter9.ppt
http://www.educypedia.be/electronics...ierclasses.htm
http://scholar.lib.vt.edu/theses/ava...cted/Chap2.PDF
http://en.wikipedia.org/wiki/Amplifier
http://www.smeter.net/amplifiers/cla...-operation.php

Last edited by Big Daddy; 03-09-2013 at 01:51 AM.
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Old 11-22-2009, 02:09 PM   #3
Blu-Dog Blu-Dog is offline
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Quote:
Originally Posted by Big Daddy View Post
This is the preliminary and unedited version. I will add more material as time permits. Please feel free to make any constructive comments. I worked on this all night long and I need to get some rest. I will be back.
My method is to hook up an IV with black coffee in it. Works like a charm.

Good stuff, man. I'm trying to figure out how bad the distortion will be running a 8 ohm receiver into 4 ohm speakers for a TV game room...it's all extra stuff, but this gives me a baseline to work from.

Thanks!
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Old 11-22-2009, 02:28 PM   #4
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Big Daddy, this is Great. and will provide much needed help and information to people here. Well Done my friend! Kudos to you for this and all that you do here buddy! D.
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Old 11-22-2009, 02:33 PM   #5
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Thumbs up

Big Daddy thank you, My head is spinning in all that great info and you brought back some knowledge I had forgotten in Tech school. I know I'll end up re-reading it a few times more.

Keep all that great info coming we sure due need it !
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Old 11-22-2009, 02:33 PM   #6
naturephoto1 naturephoto1 is offline
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Hi Big Daddy,

This part of your description is not quite accurate:

If you had a perfect amplifier and a perfect current source (wall outlet that had unlimited current availability), then each time you reduced the impedance by half, the power would be doubled. For example, an amplifier with a rating of 200 watts per channel at 8 ohms should be able to output 400 watts at 4 ohm and 800 watts at 2 ohm.

As in the case of my Aragon Palladium 1K monoblock amps they are designed to output 125 watts RMS Class A at 8 ohms; 400 watts RMS Class A/B at 8 ohms; 600 watts RMS Class A/B at 4 ohms; and 1000 watts RMS Class A/B at 2 ohms. These output wattages are due to the design of the amp; not all amps due to design double their wattage output as the impedance is reduced by half. The class A/B outputs for the Aragon Palladium II (the predecessor and basically the same design) monoblock amps were found to equal the class A/B specs at 8, 4, and 2 ohm loads in magazine tests.

My Krell KAV-250a/3 however, according to Krell outputs approximately 60 Watts RMS per channel Class A at 8 ohm; 250 watts per channel RMS Class A/B at 8 ohms; and 500 watts RMS Class A/B per channel at 4 ohms. Krell does not provide figures for 2 ohm loads and I am not sure if the amp is stable enough to maintain a 2 ohm but it may. The reviews of this amp in the magazines did confirm that these amps output a bit more (as I recall 10 to 20% possibly more) than the class A/B ratings for the amp at both 8 ohms and 4 ohms prior to clipping.

Rich

Last edited by naturephoto1; 11-22-2009 at 03:06 PM.
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Old 11-22-2009, 03:06 PM   #7
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Should there be a section that discusses the different Classes or amps -- A, A/B, D, H, etc.?

Also, do think this is the right thread to touch upon the difference between tube amps and SS amps?
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Old 11-22-2009, 03:10 PM   #8
Johnny Vinyl Johnny Vinyl is offline
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Quote:
Originally Posted by louhamilton View Post
Should there be a section that discusses the different Classes or amps -- A, A/B, D, H, etc.?

Also, do think this is the right thread to touch upon the difference between tube amps and SS amps?
Good point...and Hybrids as well.

What about Power Amps, Preamps, Integrated Amps, Receivers (stereo to multichannel).

John
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Old 11-22-2009, 03:55 PM   #9
solarrdadd solarrdadd is offline
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Quote:
Originally Posted by louhamilton View Post
Should there be a section that discusses the different Classes or amps -- A, A/B, D, H, etc.?

Also, do think this is the right thread to touch upon the difference between tube amps and SS amps?
i agree with Lou regarding the different classes of amps. Also, for you and Lou, yes, i think this is a good place to touch on the differences between tube & ss amps.

I think this is great but, for a person new with no real experience or true knowledge about amps, this will be confusing as you know what! don't get me wrong, it's great. it gets very deep into theroy and for most folks who are accounts (please, I'm not picking on accounts either) and want to get an understanding of amps (cause their thinking of getting one) a lot of this is potentially way over their heads and might even deter them from getting one because they don't understand all of the math or science assciated with it.

if i didn't have an electrical/electronics background and new nothing about this equipment, i'd be lost. i think for the majority of us, this and/or portions of it are very, very helpful. for some it will be a true lesson, for some it will be a great refresher and unfortunately for some it will thicken the fog they might be already in.

perhaps somewhere in there it can be mentioned as to what level you might need to be to grasp various things in the post relative to your experience, science and mathmatical background.

i know sometimes i catch myself talking to folks about things dealing with electricity and i see that they are lost and i have to backtrack to because they don't really understand and then they lose interest.
in that same vain, there are those who i can talk directly to and not have to breake it down, like fellow electricians and/or electrical engineers; mind you that's not always the case!

overall, i think it's very good. it will be helpfull, i know i saw a couple of things i didn't know!
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Old 11-22-2009, 04:42 PM   #10
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Vary well done Big Daddy ! Lots to learn from that .

I too , as lou mentioned would like to learn more about the differences in Classes as well !



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Old 11-22-2009, 07:20 PM   #11
Johnny Vinyl Johnny Vinyl is offline
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Quote:
Originally Posted by solarrdadd View Post
i agree with Lou regarding the different classes of amps. Also, for you and Lou, yes, i think this is a good place to touch on the differences between tube & ss amps.

I think this is great but, for a person new with no real experience or true knowledge about amps, this will be confusing as you know what! don't get me wrong, it's great. it gets very deep into theroy and for most folks who are accounts (please, I'm not picking on accounts either) and want to get an understanding of amps (cause their thinking of getting one) a lot of this is potentially way over their heads and might even deter them from getting one because they don't understand all of the math or science assciated with it.

if i didn't have an electrical/electronics background and new nothing about this equipment, i'd be lost. i think for the majority of us, this and/or portions of it are very, very helpful. for some it will be a true lesson, for some it will be a great refresher and unfortunately for some it will thicken the fog they might be already in.

perhaps somewhere in there it can be mentioned as to what level you might need to be to grasp various things in the post relative to your experience, science and mathmatical background.

i know sometimes i catch myself talking to folks about things dealing with electricity and i see that they are lost and i have to backtrack to because they don't really understand and then they lose interest.
in that same vain, there are those who i can talk directly to and not have to breake it down, like fellow electricians and/or electrical engineers; mind you that's not always the case!

overall, i think it's very good. it will be helpfull, i know i saw a couple of things i didn't know!
You make a very valid point solarrdadd. The last thing that needs to happen in any sticky is overwhelming the reader. I fear the inclusion of some of the suggestions (mine included) would probably have that effect.

John
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Old 11-22-2009, 07:56 PM   #12
naturephoto1 naturephoto1 is offline
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Quote:
Originally Posted by John72953 View Post
You make a very valid point solarrdadd. The last thing that needs to happen in any sticky is overwhelming the reader. I fear the inclusion of some of the suggestions (mine included) would probably have that effect.

John
Hi John,

I wonder if some of those ideas could be incorporated as spoilers so that they would remain hidden unless the reader wanted the additional information.

Rich
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Old 11-22-2009, 08:04 PM   #13
Johnny Vinyl Johnny Vinyl is offline
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Quote:
Originally Posted by naturephoto1 View Post
Hi John,

I wonder if some of those ideas could be incorporated as spoilers so that they would remain hidden unless the reader wanted the additional information.

Rich
Hi Rich!

Never thought of that, but sure...why not! Good idea Rich!

John
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Old 11-22-2009, 08:24 PM   #14
solarrdadd solarrdadd is offline
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Hi Rich!

Never thought of that, but sure...why not! Good idea Rich!

John
+1
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Old 11-22-2009, 08:50 PM   #15
talstarone talstarone is offline
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Another Great,Educational,Helpful,and Understandable Sticky from Big Daddy.

Incredible work on this so far BD.I look forward to using this and seeing this section grow rather quickly.
Excellent Job,Big Daddy.Your Hard Work and Willingness to Share Your Knowledge is Extremely Appreciated.

Thank You for this and ALL You do for Us and the Forum,Big Guy.Get Some Rest and Enjoy the Fruits of Your Labor.
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Old 11-22-2009, 08:53 PM   #16
solarrdadd solarrdadd is offline
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Quote:
Originally Posted by talstarone View Post
Another Great,Educational,Helpful,and Understandable Sticky from Big Daddy.

Incredible work on this so far BD.I look forward to using this and seeing this section grow rather quickly.
Excellent Job,Big Daddy.Your Hard Work and Willingness to Share Your Knowledge is Extremely Appreciated.

Thank You for this and ALL You do for Us and the Forum,Big Guy.Get Some Rest and Enjoy the Fruits of Your Labor.
Well, said, and so say we all!
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Old 11-22-2009, 09:35 PM   #17
callas01 callas01 is offline
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Maybe like others have said to define the different types of amps there are and where they may be found, and try to keep it from becoming too complicated. Although if the person is seeking an external amp, they are more then the casual HT enthusist.

Thanks for the hard work and all you do Big Daddy.
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Old 11-22-2009, 09:47 PM   #18
Jwilly019 Jwilly019 is offline
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Another great thread BD!

All of your threads are full of a ton of information, but are written in a way that anyone can understand. Thanks for all the hard work you do around here.

Justin
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Old 11-22-2009, 10:28 PM   #19
richteer richteer is offline
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Great stuff, and I like the suggestions about using spoilers. You don't want to hide the wood by the trees!

Putting my audiophile hat on for a sec, I do think that the first post should emphasise that there is no correlation between an amp's specs and its sound quality.
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Old 11-23-2009, 01:10 AM   #20
Big Daddy Big Daddy is offline
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You guys are slave drivers and sadists. You don't want to give me a break.

I added some simplified information to post #2 on amplifier classes.
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