What's the Difference Between Integrated and Power Amplifier?
An audio amplifier plays a crucial role in your audio system. It takes the low power signal from your source equipment, such as a turntable or a CD player, and magnifies it so it can be played through your speakers. They’re also widely used in public address systems and at concerts but what we’re looking at here is their application in a home sound system and what your options are when deciding what set-up will work best for you.
The audio amplifier was invented in 1906 in the form of a triode vacuum tube which could alter the motion of electrons from a filament to a plate. This had the effect of modulating the sound, a technological advance which was central to the invention of AM radio. Because its function was to increase the power of an audio signal, it was correctly described as a power amplifier. The earliest power amps used valve technology which was replaced in the 1970s by silicon transistors. By this time, amplifiers were firmly established in the consumer market and although there have been many technological advances since then, the principle remains that any audio signal needs a power amplifier to turn it into something you can listen to.
The world of hi fi systems has its own language, which is reasonably straightforward once you get used to it, but when you’re starting out and moving from all-in-one audio systems to separates, it can be baffling. Unless you can find a hi-fi dealer who doesn’t get carried away with jargon and can properly explain in layperson’s terms the functions of all the different pieces of equipment, you may find it hard to decide on the best amplifier required for your needs. You’ll hear people throwing around terms such as preamp and power amp, integrated amp, separated power and pre power. It can be easy to end up buying something that won’t do everything you want, or that duplicates the functions of other equipment. So to help you make sense of it all, let’s return to our original question: ‘What's the difference between integrated and power amplifier?’
What is a Power Amp?As we’ve touched on already, power amps have one job to do. They amplify the line level audio signal from any music source to a level that can drive the speakers. The result is known as a speaker level signal. Most audio devices - turntable, CD player, streamer, MP3 player - can transmit only line level signals which are much weaker than speaker level signals. If you plug anything other than powered speakers into your source without the mediation of a power amp then you won’t get any sound output. With vinyl all you’ll hear is a barely audible whisper of sound coming directly from the stylus in the groove. As for digital equipment, you’ll hear nothing.
What is a Preamp?
Before we look at the integrated amplifier we need to understand the function of another piece of equipment, the preamp. We’ve already talked about how a power amp boosts the line level signal to a speaker-level signal fit for the speakers. But the relationship between the preamp and power amp is just as important.
There are several steps in the signal path and each one is known as a gain stage. The term gain describes the transformation in power of the signal. The reproduction of music starts with a microphone or instrument level signal. A preamp boosts this to a line level signal. The same sequence applies in a recording studio but in a home audio system the preamp has a second function. Not only does it boost the signal, but it also selects between the different sources, via analog or digital input, making it possible to use several players with little or no manual operation. The more devices you connect, the greater the benefits of a preamp which is essentially the control center for your system, providing the proper signal routing, optimum performance and genuine high quality audiophile sound. Some preamps are made without tone control, but we think it’s important to have this facility.
What is an Integrated Amplifier?Now that we’ve covered the basics of the preamp and power amp, we’re going to throw something else into the pot: the integrated amplifier, or pre power amp. As its name suggests, it is a unit in which both preamp and power amp functions are combined. An integrated amp has extra circuitry for the preamp function, including a gain knob and often a tone control and a volume control.
In some ways, it makes a lot of sense to use an integrated amplifier rather than two separate units for preamp and power. It’s generally cheaper, simpler to set up and takes up less space. However, there are some disadvantages too. The circuitry you’ll find in a preamp tends to be more delicate than that of a power amp. Because an integrated pre power amplifier contains both, it follows that the integrated unit can also be quite delicate.
In contrast, a power amplifier, being a single unit, isn’t affected by this. They don’t have to cope with an additional component which can impair the audio signal with distortion or interference. Furthermore, in an integrated unit the preamp and power amp parts usually draw their power from the same power supply, which can also affect the sound quality. If you’re looking for minimal interference, a power amp may be the better option.
So if you’re wondering why audiophiles insist on having separate preamps and power amps it’s not because they’re purists - although they probably are - it’s simply because experience has taught them how to get the best results. There is a general consensus among enthusiasts that only strict adherence to the idea of separates will achieve the best results. It also makes it considerably easier to upgrade parts of your system without having to replace more than necessary. If you need more power, then you just have to buy a bigger power amp and hook it up to the other components Having said that, the difference in performance can be fairly minor so if convenience and cost are important to you then there’s no reason not to go for an integrated amp.
There are, in fact, some engineering advantages to having all the amplification functions located in one box because it enables the low-level source signals to be isolated from the integrated amplifier, which is using a huge transformer and enormous power transistors to boost them. In addition, despite the potential for interference and distortion, some integrated amplifiers allow the source signals to be generated cleanly by using not a single power supply but separated power sources that are designed not to interact with each other, thereby reducing distortion in the audio signal at the preamp stage.
Some of this discussion is based on the long-established historical differences between integrated amp and power amp designs. So where do things stand today? With the advance in modern digital sources, flat output has become commonplace. The term describes what many see as the ideal frequency response. This is one which doesn’t make any adjustments to the bass, middle or treble registers. Where you’re dealing with flat response, the separate pre-amplification process is no longer essential. However, we’re some distance away from perfection in flat output, particularly with headphone drivers and speakers, where various mechanical properties, acoustics and electronics can create non-linearity which has a detrimental impact on the sound quality. Therefore, for the time being, all the functions remain important.
Using an Integrated Amplifier and a Power Amplifier TogetherAre you still confused? Stick with us because although it’s complicated, we’ll get there in the end. We’ve discussed the functions of the different types of amplifier and gone over some of the pros and cons, answering the question ‘What's the difference between integrated and power amplifier?’ Implicit in that question are two others: ‘which is best?’ and ‘can you use them together?’
In our experience, there’s no definitive answer to which is the best option, because as we’ve seen, there have always been advantages and disadvantages to both. Meanwhile, designers of hi fi systems are coming up with new designs to even out the performance of the two, chiefly in the matter of distortion. If we can look forward to the day when that problem is comprehensively solved, there really will be virtually nothing to choose between them apart from cost and the greater convenience of an integrated amp.
The question about using them together is a little more interesting. The purpose of an integrated amp is to handle in one place the functions of the preamp and power amp. However, if you decide you’re not happy with the level of power being supplied to your speakers then you could consider adding a separate power amp to your setup, or perhaps even powered speakers which is another debate entirely. Obviously, this will make the power amp function of the integrated unit redundant but it’s still a more cost effective choice than doing away with the integrated amp all together and replacing it with separates.
You can add a power amp by plugging it into the preamp output of the integrated amp. By doing this, you can send audio signals directly from the preamp inside the integrated amp (are you still following?) to the stand-alone power amp. The result is an increase in the power that drives your speakers. This may be helpful if you’ve invested in new speakers that need an extra boost. Adding a power amp increases the strength of the audio signal by raising the voltage and current, thereby improving the sound.
However, adding a power amp is not without its problems. You run the risk of generating unpleasant background noise within the audio signal and distortion in the sound that comes out at the other end. This is usually referred to as noise floor. If you turn up the volume control on your speakers with everything switched on but no music playing, if you hear a hissing sound then you’ve identified the noise floor. Most audio that runs through an amp will inevitably contain a certain amount of noise. This might be caused by the audio source, even with the best analog and digital input, or it could be the result of faulty cables or the quality of your equipment. When you process audio signals through an amp, then any noise within those signals will also be amplified. Adding a power amp to an integrated amp means both the signal and its unwanted noise are amplified twice. You end up with a higher noise floor.
A word of warning: not all integrated amplifiers come with a preamp output, so if you have one of these models then you don’t have any way of connecting a separate power amp. When you’re working out the right amplifier required for your present and future plans, bear this in mind.