In the days when people used phonographs, the quality of your cartridge and tonearm was very important because a cheap cartridge and tonearm could literally destroy an entire record collection. It was wise for people to spend a little money and avoid damaging their collections. In the day of CDs and DVDs, customers are free to buy very cheap equipment because no matter how cheap, it will not damage anything.

Deciding on what amplifier to buy is a personal choice based primarily on budget and lifestyle. I hope this article helps explain what you can expect to get for your money and help you make a more informed decision. Several years ago, Julian Hirsh writing for Stereo Review stated that all amplifiers sound the same. Julian Hirsh was attacked for making this statement yet when Stereophile did blind testing between several different amplifiers, the listeners could not accurate pick out which amplifier they were listening to.

What does this all mean? Does an amplifier play an important role in the audio chain or not?

I believe that amplifiers play a very important role in the audio chain. I also believe with some experience, it is fairly easy to tell the quality of one amplifier versus another.

The problem is it is difficult to compare an amplifier against an amplifier. The best way to compare an amplifier is against real music. There is probably no better way to listen to an amplifier than to listen to recorded piano music. In my experience, very few amplifiers can capture the sound of a real piano. In fact, some of the very most expensive amplifiers fall short on this test.

Receivers

Receivers offer the best value for someone putting together an audio system. Minisystems and department store systems usually offer very low quality speakers as part of the package so these are rarely good values. A receiver gives you a control amplifier (preamp), amplifier, and tuner (and in the case of an Audio Video (AV) receiver, digital processing). The price for a receiver is the least expensive way to acquire all the components required to put together a high fidelity system.

Receivers are by definition a very good value. However, receivers never offer the ultimate in audio reproduction. It is my opinion that buying a receiver is a means of economizing and that people who purchase receivers should buy towards the middle of the receiver line and look for sales because no matter how expensive or what brand you receiver is (with the exception of companies such as B&K or Macintosh), receivers are simply not going to sound all that different from one another.

Integrated Amplifiers

The least expensive integrated amplifiers are receivers without tuners. Most of the Japanese made integrated amplifiers offer little or no sonic advantage over a receiver. There are companies such as Krell, Plinius and Arcam that manufacture integrated amplifiers that offer a very high level of performance--if not the ultimate. It is possible to get very high quality sound from some integrated amplifiers. Integrated amplifiers typically offer smaller power supplies than separate amplifiers and use preamp components that don't quite match the best found in the highest quality preamplifiers. None-the-less, an integrated amplifier can offer very good value.

Separates

Integrated amplifiers and receivers have their own switching facilities and volume controls. Separates require an additional component to do switching and volume adjustment. Generally speaking, separates represent the ultimate in amplification. There is a wide range of products sold in this category.

The biggest point of contention among audiophiles is which is better--tube amplifiers or solid state. There is no question that solid state equipment is more efficient, tests better and is more reliable. However, a large segment of the audiophile community say that tubes sound more lifelike and that transistors are too clinical. I find that this is more a political argument than a technical one. Tube supporters are more vocal than solid state supporters.

I have found good and bad examples of both tubes and solid state equipment. The worst tube amplifiers are slow and have a sound often called tube grunge. The best tube amplifiers sound absolutely spectacular. The same is true for solid state. Some solid state amplifiers seem to suck the life out of the music. Other amplifiers absolutely communicate the moment. The problem is that it is hard to tell simply by the price tag which amplifier is the best sounding. Some amplifiers that cost big dollars seem slushy to me. They seem to be created to sound like they think a great tube amp should sound rather than how a great amplifier should sound.

Classes of Amplifiers

Amplifiers do not actually increase the strength of an electronic signal. What happens instead, the signal is copied and enlarged. There are different schemes for amplifying the signal. There are different classes of amplifiers. These classes are A, AB, and C. There have been some special classes such as G, created by Hatachi. Class H created by Soundcraftsman. Class D for the so-called digital amps and Class T for Tripath's digital amplifiers.

Class A amplifiers use one or more transistors that conduct during both the positive and negative cycles of the signal. This Class of amplifier has the lowest distortion but it is very inefficient and generates a lot of heat. A Class A amplifier requires that the amplifier generate the full current no matter what the output is. If you were simply listening to FM or watching a movie, the amplifier would be consuming as much power as if you had it turned up to full volume.

In order to increase efficiency, Class B amplifiers use one transistor to conduct the positive portion of the waveform and another transistor to conduct the negative portion of the waveform. 99% of all audio amplifiers today are Class B. Class B amplifier can be built today so that its distortions are well below what the human ear can detect and nearly to the point where it is unmeasurable.

Many amplifiers call themselves Class A/B. In reality, very few are. Early Class B amplifiers had a problem known as switching delay. In a class B design, a transistor works 50% of the cycle while another transistor works 50% of the cycle. In early class B amplifiers, there was a distortion created between the time the devices were switching back and forth. Some people referred to this distortion as notch distortion because there was a notch appearance on an oscilloscope between the two waveforms.

Class A/B was created to leave the transistor conducting while the second transistor was conducting. This created an overlap between the two signals. The problem with this approach is that it created its own distortion called gumming. This means that the signal would get a little fatter where the two devices were both conduction.

Today, if you look at a properly designed Class B amplifier on a scope, you will see no switching distortion.

Class D amps are sometimes called digital amplifiers. There is really no such thing today as a digital amplifier. A Class D amplifier uses transistors that are either switched on or off to represent positive or negative values. The transistors are either on or off. The advantage of such a system is that it is highly efficient and generates very little heat. The disadvantage is that there can be a distortion caused between the switching of the positive and negative transistors as the positive and negative transistors can not be on at the same time.

Many Class D amplifiers are finding their way into Subwoofers. They are inexpensive to build and the logic is that the switching distortion is not important in a subwoofer.

Class T amps are a more refined switching amplifier developed by Tripath. It uses signal processing to eliminate the switching distortion of Class D. nOrh is currently working with parts from Tripath to determine the sonic merits using the Tripath parts. Our current view is that advantage to using Class T and Class D amps is not to achieve better sound than can currently be achieved with standard A or A/B amplifiers. Rather it is an attempt to create a lower priced amplifier that offers good performance.

Probably 90% of the amplifiers on the market are designed to get a particular RMS rating and little consideration is provided to provide any extra power from the power supply. A properly designed power supply requires three times the output from the power supply than required to drive the amplifier to its maximum RMS rating. Buying and shipping large transformers is very expensive. Manufacturers are looking for ways to cut these costs.

At nOrh, we over design and overbuild our power supplies. Our new subwoofer amp has a massive 600 V/A R-Core transformer. The Multiamps have two massive R-Core transformers that are specially built to offer the highest speed possible. It is important to remember that classes of amplifiers do not describe quality but rather topology.

Tubes vs. Transistors

Transistors are far more popular than tubes. However, there are a group of audiophiles who continue to swear by tubes. Solid State amplifiers are more reliable, test better and are usually less expensive. None-the-less, many audiophile believe that transistors sound clinical. There has been a resurgence of tube amplifiers in the past few years. The main reason is that Russia and China never stopped producing tubes. These tubes are entering the market and creating a new source for tubes.

Tube amplifiers are said to sound more musical. The reason is that tube amplifiers produce even ordered harmonics. Musical instruments give off harmonics in even orders. Transistor amplifiers tend to give off harmonics that are odd ordered. These harmonics are not pleasing to the ear as second order harmonics are. Modern solid state amplifiers have very low distortions but their distortions are less tolerated by the ear than even ordered harmonics.

One should note that while most solid state amplifiers have very low distortions (Total Harmonic Distortion) for the left and right channel, other channels are often much higher as these specifications are rarely noted.

One should note that while most solid state amplifiers have very low distortions (Total Harmonic Distortion) for the left and right channel, other channels are often much higher as these specifications are rarely noted. Subwoofer amplifiers are particularly bad at creating odd ordered harmonics. I believe that the best tube and solid state amplifiers sound amazingly alike. Bad tube amplifiers sound tubby and slow. Bad transistor amplifiers sound harsh, bright and strident.

Just like you can't judge a good book by its cover, you can learn very little about an amplifier without digging in and seeing what is inside. Generally speaking, the most important component of any amplifier is its power supply. It is sufficient? Is it accurate? Is it fast? Unfortunately, almost no amplifier company talks about their power supplies or what transformers they use. I think most manufacturers would prefer you not ask.

Balanced Inputs - I get lots of questions about balanced inputs. Most people want to know do they sound better or not? We have to look first what true balanced inputs do. Balanced inputs are used for professional gear. What happens is that the signals between two amps are compared. One signal is in positive phase and the second is in negative phase. Noise will appear to be in the same phase to the noise component can be eliminated.

Some very expensive high-end equipment features balanced inputs. Most of these are gimmicks. The reason is that in order to compare the two signals, you literally have to have two amplifiers for every one. What most high-end equipment manufacturers do is they provide balanced connectors (called XLR connectors) and then convert this to a standard signal. The benefit is that it allows you to use XLR connectors instead of RCA connectors. It doesn't offer the ability to drive longer cables and eliminate noise.

nOrh doesn't believe in gimmicks so if we ever see the need to offer balanced inputs, it will be using a true balanced system. Also, check out "advanced amplifier concepts" linked below.