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Golden Rule: One amplifier cannot "improve" the original sound compared to another. Rather, one amplifier will simply "degrade" the original signal less than the other.
For the list of Pre/Pro manufacturers with HDMI 1.3 I/O and HD audio support, go to post #2.
Figure 1 shows the schematic diagram of a very basic DC circuit. It consists of nothing more than a source (a producer of electrical energy) and a load (whatever is to be powered by that electrical energy). The source can be any electrical source: a chemical battery, an electronic power supply, a mechanical generator, or any other possible continuous source of electrical energy. For simplicity, we represent the source in this figure as a battery.
Figure 1
At the same time, the load can be any electrical load: a light bulb, electronic clock or watch, electronic instrument, or anything else that must be driven by a continuous source of electricity. The figure here represents the load as a simple resistor.
Regardless of the specific source and load in this circuit, electrons leave the negative terminal of the source, travel through the circuit in the direction shown by the arrows, and eventually return to the positive terminal of the source. This action continues for as long as a complete electrical circuit exists.
Now consider the same circuit with a single change, as shown in the second figure 2. This time, the energy source is constantly changing. It begins by building up a voltage which is positive on top and negative on the bottom, and therefore pushes electrons through the circuit in the direction shown by the solid arrows. However, then the source voltage starts to fall off, and eventually reverse polarity. Now current will still flow through the circuit, but this time in the direction shown by the dotted arrows. This cycle repeats itself endlessly, and as a result the current through the circuit reverses direction repeatedly. This is known as an alternating current.
Figure 2
This kind of reversal makes no difference to some kinds of loads. For example, the light bulbs in your home don't care which way current flows through them. When you close the circuit by turning on the light switch, the light turns on without regard for the direction of current flow.
Of course, there are some kinds of loads that require current to flow in only one direction. In such cases, we often need to convert alternating current such as the power provided at your wall socket to direct current for use by the load. There are several ways to accomplish this, and we will explore some of them in later pages in this section.
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.
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 semiconductor devices used inside the electronic equipment require DC voltage. Many different types of power supplies are used in amplifiers. High quality amplifiers have totally independent power supplies, one for each channel.
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.
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. In the real world, amplifiers have real power supplies and their 4 ohm power rating is usually not twice as high as the 8 ohm rating, despite what the manufacturer claims.
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 total output. However, the fine print also states that this power output is with 10% total harmonic distortion, and usually over a limited frequency range like 40-18,000Hz.
It is important to know that power can not be amplified. Voltage and current can be amplified. The term "power amplifier" is technically incorrect.
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. Generally, distortion below 1% is considered to be excellent. Human ears are imperfect and cannot really distinguish between distortion levels below 1%. Don't fall for the marketing hype.
Signal-To-Noise (S/N) Ratio: The higher number is better.
Continuous Power: Just because the receiver 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 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.
SHOULD WE BE CONCERNED IF AN AMPLIFIER'S POWER RATING IS HIGHER THAN A SPEAKER'S POWER CAPABILITY?
You have to distinguish between the maximum capability of the amplifier and how much power you are giving to your speakers at any given time by turning the volume up and down.
Let's assume you have speakers that are rated at a maximum capabilty of 50 watts. It is perfectly safe to use an amplifier that is rated 1,000 watts per channel. An amplifier like that has plently of reserve power and will never clip because of power limitation.
FAQ
Q. Does this mean that as soon as you connect this amplifier to the speakers, the speakers will blow? A. Absolutely not. At any given time at normal listening level, you are probably using a few watts. Occasionally, during a peak, the amplifier may be required to provide more current for a second or less. A big powerful amplifier will have enough reserve power to provide what is needed. A weaker amplifier will not have enough reserve power and will clip (will go beyond its capability). Clipping will not instananeously damage the amplifier or the speakers. However, if it happens periodically over a certain time period, it may cause damage to the amplifier and/or to the speakers.
Q. Can you damage the speakers with a 1,000 watt amplifier? A. Yes, if you turn the volume up and make the drivers go beyond their capability and over-extend, you can certainly damage the speakers.
Q. Can we damage the speakers by turning the volume down? A. NO. I don't know where this idea has come from. Everytime I hear it, I suffer from acid indigestion for the next 24 hours.
Q. Can you damage a 50 watt speaker with a 20 watt amplifier? A. Yes, you can. If you turn the volume up enough, the weak amplifier will not have enough current to provide and will distort. It may not damage the speaker immediately, but if it happens a few times, it will.
Q. What is the most important culprit in causing damage to the speakers? A. That damn
[Show spoiler]VOLUME dial.
It makes the amplifier and the speakers go beyond their capability.
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.
ADVANTAGES & DISADVANTAGES OF RECEIVERS VS SEPARATE AMPLIFIERS
Advantages of Receivers
A receiver consists of four components:
Preamp to do all the switching and input/output matching.
Processor to process audio codecs such as DD, DTS, Dolby TrueHD, DTS-HD MA, PCM, etc.
Tuner to provide radio functions such as AM/FM.
Multi-channel amplifiers to amplify the audio signals and send them to the speakers..
Receivers are convenient.
Receivers are affordable.
Receivers take less space
Disadvantages of Receivers
In a receiver, the four components above share the same power supply, circuits, etc.
Many compromises in the design of receivers.
Receivers have less power than amplifiers (less than 170 watts).
In many cases, receivers cannot output their stated power when all the channels are driven at the same time.
Receivers may not be able to drive high quality, large, and inefficient speakers.
Most receivers may have difficulty driving 4 ohm speakers.
Audio quality is not as good as separates.
They have less headroom and may clip faster.
May generate too much heat.
Advantages of Amplifiers
Amplifiers have their own higher-quality power supply.
Some high-end amplifiers have a different power supply for each channel.
Amps do not share their parts with any other components.
Generally speaking, amplifiers have more wattage. Some can handle 500 watts or more.
They can output cleaner power and in most cases, capabable of outputting as much as they are rated for, even when all the channels are driven.
They have a lot more headroom and do not clip as easily. This allows you to receive the maximum benefit from the superior dynamic range of Blu-ray movies and SACD/DVD-A music.
They can easily drive 4 ohm speakers.
Audio quality is much better.
Can mix and match with speakers and other components.
You can brag more.
Disadvantage of Amplifiers
They are less convenient.
You normally need three components to do the job of one receiver.
They can take more space.
They are more expensive.
Your electric bill may run higher.
Setup can be more complex.
I use my Denon receiver as a Pre/Pro. I only use the pre-amp portion and the built-in audio codecs of the receiver. I use separate amplifiers to drive all my speakers. Even my subwoofers are passive and are driven by separate amplifiers. The speakers have different impedances. The amplifiers handle them with ease and can play very loud without clipping.
Amplifiers' Power Ratings
Amplifier power ratings are important because amplifiers do the work of making loudspeakers produce sound. (Receivers incorporate amplifiers, so everything said here about amps applies to them as well.) And the more power something has, the more work it can do. So all else being equal, the more watts available the better. A more powerful amplifier should be able to play louder without distortion than a less powerful one. Here's where it starts to get tricky. Sometimes you may hear or read someone saying that a particular amplifier sounds more powerful than one with a higher power specification. Sometimes that's just evidence of an overactive imagination at work, but such things really do happen. There are two main reasons, one having to do with how manufacturers specify power, the other with what is involved in delivering power to a loudspeaker. Rating games. More than 20 years ago, the Federal Trade Commission (FTC) laid down rules for how power specifications for home audio amplifiers could be advertised. Basically, the rules require manufacturers to declare how much average (as opposed to peak) power an amplifier can deliver into a stated impedance over a stated bandwidth with a stated maximum level of distortion and with all channels driven simultaneously. They also require that the primary specification be for an 8-ohm impedance. A manufacturer can list specs for other impedances, but they must be subsidiary to the 8-ohm rating. (We'll get into the significance of that restriction later when we discuss delivering power to speakers.) A typical stereo amplifier power specification might thus read something like the following: 100 watts per channel into 8 ohms from 20 Hz to 20 kHz with no more than 0.1% THD (total harmonic distortion), both channels driven. Although one can quibble with some details of the FTC strictures, they are basically good in that they force amp makers to give the most important specification in a form that is readily comparable from brand to brand and model to model. There is still some wiggle room, however. For example, a manufacturer can usually report more power for his amplifier if he raises the distortion threshold or narrows the bandwidth. The same amplifier described in the last paragraph might also be (legitimately) rated as follows: 115 watts per channel into 8 ohms at 1 kHz with no more than 0.8% THD, both channels driven. Another interesting dodge has emerged in the home theater era, based on the fact that so many amplifiers and almost all receivers now have five channels rather than just two. Yet many five-channel amps and, especially, receivers sport power ratings based primarily or exclusively on two-channel operation, or on some other combination short of all channels driven simultaneously. Reason: The fewer channels operating, the more power the ones that are running can deliver. So the manufacturer can say he's got, say, a 120-watt amplifier instead of a 100-watter. It's just a matter of less competition for the amplifier's power-supply resources. The argument for this method of specification is that it is more realistic, since it is very rare that all five channels would be required to deliver full power simultaneously anywhere except on a test bench. Unfortunately, it also can be used to paper over design shortcomings. And since there is not much uniformity in how manufacturers apply this sort of rating method, it makes comparisons more difficult. At Harman, we think the fairest, most honest, and most revealing rating method is the obvious one: to specify power with all channels fully driven. And that's how we do it for our products. Delivering power to speakers. The other thing that complicates making sense of amplifier power specs is that loudspeakers are complex loads. For simplicity and ease of comparison, amplifier power measurements are made into purely resistive loads, usually 8 ohms. But speakers, almost without exception, present complex impedances. That means their impedances contain reactive (inductive and capacitive) elements as well as resistive ones, which in turn means that their impedances vary with frequency. A speaker having a nominal impedance rating of 8 ohms will have that actual impedance at some frequency or frequencies, but you might reasonably expect it to go down to 5 or 6 ohms (or below) at others and much higher at still others. The rated impedance is thus an approximation, at best. Why does that matter? Let's consider what a watt really is. Power (watts) is voltage (volts) times current (amperes, or amps): 1 volt x 1 amp = 1 watt. An audio amplifier normally is designed to approximate what is known technically as a "constant-voltage" device, meaning that a given voltage in will yield a given voltage out, determined by the amplifier's gain. Put 1 volt into an amplifier with a gain of 10, and you should get 10 volts out. How much current you get out is then determined by the impedance of the device the amplifier is driving. Assuming a perfect amplifier, current out should equal voltage out divided by the load impedance. Consequently, halving the impedance (going from 8 to 4 ohms, for example) should double the current. And since power is voltage times current, that means the power should double as well. With real amplifiers, however, it usually won't. The main reason is that amplifier output transistors are limited in how much current they can transfer without overheating and destroying themselves. A designer can get around this problem by using more robust transistors, or simply more transistors, but that drives up cost. Any practical amplifier will therefore have some limit on the amount of current it can deliver, set primarily by the output transistors, just as it will have a limit on its output voltage, determined primarily by the design of the power supply (if not the AC line voltage). The design engineer has to decide what those limits will be, based on some cost/benefit analysis. Because amplifier power tends to be specified mainly for 8-ohm loads, there is a commercial incentive to concentrate on the voltage side of the equation, because into 8 ohms that will normally be the limiting factor. Unfortunately, loudspeakers often present a lower impedance–somtimes a much lower one–right in the frequency range where much musical energy is concentrated. And for reasons too complicated to get into here, reactive impedances, such as those presented by loudspeakers, can often draw more current than the simple magnitude of the impedance would suggest. An amplifier designed with inadequate concern for current capacity may therefore fail to perform up to the promise of its power spec when it is required to drive loudspeakers instead of 8-ohm laboratory resistors. You can guard against this problem by looking for a 4-ohm power specification–preferably one that is at least 50% above the 8-ohm spec. It is also a good (though not infallible) sign if the manufacturer makes a point of current capability in describing its amplifiers and receivers. One last thing that can affect amplifier power specifications is simply how conservative the manufacturer is in rating its products. Is the goal to print the best possible spec or, perhaps, to ensure that the customer will get the rated output even if the AC line voltage at his home is only 110 volts rather than 120? This is hard to assess except by reputation and track record, but it is a significant factor.
Quote:
Loudspeakers
Power specifications for speakers are a somewhat simpler matter. In the case of passive speakers (those without internal amplifiers), any power rating will be for how much the manufacturer thinks the speaker can take without damage. (Or, in some instances, the minimum the manufacturer thinks the amplifier should be able to provide in order to provide satisfactory listening levels.) Unfortunately, the amount of power a speaker can take is a complex function of spectral energy distribution (the relative proportion of energy versus frequency) and duration. So there really is no one definitive number. Worse, no universally accepted standard exists for determining speaker power handling, which means that two different manufacturers could come up with entirely different numbers. About all you can determine from speaker power-handling specs is whether one model in a company's line can take more punishment than another. You can't compare realistically between brands, and even within a brand, you can't take the absolute numbers too seriously. This is true for powered speakers as well, though for different reasons. By powered speakers, we mean those that have their own internal amplification. Very few full-range speakers are fully powered, though there has been a trend in recent years building in woofer amplifiers. Most separate subwoofers, on the other hand, do incorporate their own amplifiers. When a speaker does include amplification, the manufacturer usually will give a power rating for that amplifier–which you should simply ignore. If power is so important a specification for separate amplifiers and receivers, why isn't it for a powered speaker or subwoofer? Actually, it is important, but only to the designer. He's the one who has to figure out what combination of speaker sensitivity and amplifier power will yield the desired sound output capability, which is what really matters. What you need to know is how loud the speaker or subwoofer can play over what frequency range and with how much distortion. In other words, you need to know what's coming out of the speaker, not what's going into it. It is entirely possible, for example, that a subwoofer with a 100-watt amplifier could outperform one with a 200-watt amp in every respect. For a consumer, the power rating of an amplifier built into a speaker is an absolutely useless number. In addition, there is the matter of the accuracy of such ratings. Because amplifiers built into speakers or subwoofers are inaccessible, it is rare that anybody checks how much power they can really deliver. Power numbers sell, which creates a temptation to–how shall we put this delicately–exaggerate that some companies find irresistable. Just one more reason to ignore them.
Boulder was already in there. The Wavac is $350,000 and the Goldmund is $108,000. In some parts of the country, you can buy a house for less than $350,000.
There has been a lot of hot chatter on the E-mail circuit over the past couple of months about the Steve Maki and Steve Zipser challenge in Miami. I thought you would appreciate a complete recount of the events. Zipser, a high-end salon owner, had issued a challenge that he would pay the airplane fare of any in- terested party who wanted to see him prove he could hear the differences be- tween amplifiers.
On Sunday afternoon, August 25th, Maki and I arrived at Zipser's house, which is also Sunshine Stereo. Maki brought his own control unit, a Yamaha AX-700 100-watt integrated amplifier for the challenge. In a straight 10-trial hard- wired comparison, Zipser was only able to identify correctly 3 times out of 10 whether the Yamaha unit or his pair of Pass Laboratories Aleph 1.2 monoblock 200-watt amplifiers was powering his Duntech Marquis speakers. A Pass Labs preamplifier, Zip's personal wiring, and a full Audio Alchemy CD playback system completed the playback chain. No device except the Yamaha integrated amplifier was ever placed in the system. Maki inserted one or the other amplifier into the system and covered them with a thin black cloth to hide identities. Zipser used his own playback material and had as long as he wanted to decide which unit was driving the speakers.
I had matched the playback levels of the amplifiers to within 0.1 dB at 1 kHz, using the Yamaha balance and volume controls. Playback levels were adjusted with the system preamplifier by Zipser. I also determined that the two devices had frequency response differences of 0.4 dB at 16 kHz, but both were perfectly flat from 20 Hz to 8 kHz. In addition to me, Zipser, and Maki, one of Zip's friends, his wife, and another person unknown to me were sometimes in the room during the test, but no one was disruptive and conditions were perfectly quiet.
As far as I was concerned, the test was over. However, Zipser complained that he had stayed out late the night before and this reduced his sensitivity. At dinner, purchased by Zipser, we offered to give him another chance on Monday morning before our flight back North. On Monday at 9 a.m., I installed an ABX comparator in the system, complete with baling-wire lead to the Yamaha. Zipser improved his score to 5 out of 10. However, my switchpad did develop a hang-up problem, meaning that occasionally one had to verify the amplifier in the cir- cuit with a visual confirmation of an LED. Zipser has claimed he scored better prior to the problem, but in fact he only scored 4 out of 6 before any difficulties occurred.
His wife also conducted a 16-trial ABX comparison, using a 30-second phrase of a particular CD for all the trials. In this sequence I sat next to her at the main listening position and performed all the amplifier switching functions according to her verbal commands. She scored 9 out of 16 correct. Later another of Zip's friends scored 4 out of 10 correct. All listening was done with single listeners.
In sum, no matter what you may have heard elsewhere, audio store owner Steve Zipser was unable to tell reliably, based on sound alone, when his $14,000 pair of class A monoblock amplifiers was replaced by a ten-year old Japanese integrated amplifier in his personal reference system, in his own listening room, using program material selected personally by him as being especially revealing of differences. He failed the test under hardwired no-switching conditions, as well as with a high-resolution fast-comparison switching mode. As I have said before, when the answers aren't shared in advance, "Amps Is Amps" even for the Goldenest of Ears.
ADVANTAGES & DISADVANTAGES OF RECEIVERS VS SEPARATE AMPLIFIERS
Advantages of Receivers
A receiver consists of three or four components: preamp/processor (all the switching and processing are done there), Tuner (AM/FM), and an Amplifier.
Receivers are convenient.
Receivers are affordable.
Receivers take less space
Disadvantages of Receivers
In a receiver, the three components above share the same power supply, circuits, etc.
Many compromises in the design of receivers.
Receivers have less power than amplifiers (less than 170 watts).
Receivers may not be able to drive high quality, large, and inefficient speakers.
Most receivers may have difficulty driving 4 ohm speakers.
Audio quality is not as good as separates.
They have less headroom and may clip faster.
May generate too much heat.
Advantages of Amplifiers
Amplifiers have their own higher-quality power supply.
Some high-end amplifiers have a different power supply for each channel.
Amps do not share their parts with any other components.
Generally speaking, amplifiers have more wattage. Some can handle 500 watts or more.
They have a lot more headroom.
They can easily drive 4 ohm speakers.
Audio quality is much better.
Can mix and match with speakers and other components.
You can brag more.
Disadvantage of Amplifiers
They are less convenient.
You normally need three components to do the job of one receiver.
They can take more space.
They are more expensive.
Your electric bill may run higher.
Setup can be more complex.
I use my Denon receiver as a Pre/Pro. I only use the pre-amp portion and the built-in audio codecs of the receiver. I use separate amplifiers to drive all my speakers. Even my subwoofers are passive and are driven by separate amplifiers. The speakers have different impedances. The amplifiers handle them with ease and can play very loud without clipping.
I have done some testing with the receiver versus amplifier. The audio quality of the amplifiers is significantly better.
Very interesting.
A few questions...
1. What size, and price, of speakers justifies buying seperates?
2. Should Blu-ray users seek out seperates, since decoding is usually done onboard Blu-ray players?
3. How much is the minimum one could expect to spend on a system of seperates that would be better than A/V reciever like Onkyo 706 or Marantz SR6003, etc?
Last edited by Travis; 03-01-2009 at 01:29 PM.
Reason: spelling
A few questions...
1. What size, and price, of speakers justifies buying seperates?
2. Should Blu-ray users seek out seperates, since decoding is usually done onboard Blu-ray players?
3. How much is the minimum one could expect to spend on a system of seperates that would be better than A/V reciever like Onkyo 706 or Marantz SR6003, etc?
These are three very difficult questions to answer. The answers are very subjective and depend on the person's taste, hearing, and budget.
Speaker quality is a very subjective matter. As a general rule, the better the speakers, the more separates will enhance your audio experience. If you want a cutoff price, my guess would be over $1,000.
Yes, with blu-ray HD audio, separates will benefit you more.
This is another subjective answer. If you are on a tight budget, Emotiva is your best bet. If money is no object, there are amplifiers that have 5 or 6 figure prices. On the average, almost all quality pre/pro and amp combinations will outperform the vast majority of receivers. In addition, many high-end speakers have low impedance and require separates.
Looks like $2,000+ to start an upgrade with seperates, saw some interesting budget stuff Marantz 8003, and Onkyo PR-SC885. This might be what I am intersted in, Onkyo should be paired with what amp? Don't want to be picky, but if I buy seperates I'd like them to match, same brand and series.
Looks like $2,000+ to start an upgrade with seperates, saw some interesting budget stuff Marantz 8003, and Onkyo PR-SC885. This might be what I am intersted in, Onkyo should be paired with what amp? Don't want to be picky, but if I buy seperates I'd like them to match, same brand and series.
While staying within certain brands is a good thing with some manufacturer's it isn't necessary most of the time. A good amp doesn't expire and will last basically forever. Amp technology doesn't change rapidly like it does with pre/pro's or receivers and that is also why getting into separates can be a great idea. Keep the amps and upgrade the pre/pro as technology advances. With receivers it's kind of like throwing out the kitchen sink with the water, and that's not the case with separate components.
Buying a good amp can really pay off as well and really be great for the owner. Take for example Bryston and the fact their amps, not sure if it's all models but anyhow, they come with a twenty year warranty. Very nice to have that kind of service and protection and I also think that warranty is transferable to the next owner if you sell it or buy a used one from somebody !!!
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Amplifier & Pre/Pro Manufacturers
high end makers include:
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