An amplifier, or receiver(an amplifier with a radio tuner) ideally should not affect the sound quality at all, it should just make the sound louder. This is unfortunately theoretically impossible but it is the ideal that amplifier designers and engineers have been striving for ever since the first recorded audio. The reason that this pot of gold at the end of the rainbow will never be found is a nasty thing called distortion. The electronic devices that are used to increase the volume have distortion and the cheaper the device the more distortion they are going to create. There are two ways that a designer can combat these distortions. You can continue to use inexpensive components in the amplifier and employ another small amplifier called a negative feedback amplifier that injects a reverse wave of the distortion element into the signal and the 2 waves cancel each other out. This would work great if we all didn’t have to deal with a little constant called time. Even though we are dealing with the speed of electricity in wires there is still a time shift that happens when negative feedback is used and the distortions (inter modulation distortion) that this creates is much more annoying to our ears than the original distortion that it was designed to lessen.
The best way to combat distortion is to use the best quality components in the design of your amplifier. A small amount of harmonic distortion can be tolerated a lot easier by the human ear than the same amount of intermodulation distortion. Tube electronics generate a very natural distortion called even order harmonic distortion. This is actually a distortion that the human ear perceives as tolerable, this type of distortion occurs naturally in our every day lives, from a dog barking to a barbershop quartet, they all contain even order harmonics to create the sound we hear. Transistors on the other hand create odd order harmonics. These harmonics do not occur naturally and so our ears are much more intolerant to these sounds. Although distortion can’t be eliminated transistors can be tested and manufactured to a very close tolerance to lessen the percentage of distortion that they contain. Integrated circuits (the kind of device found in almost all inexpensive audio systems (from an ipod to a home theater in a box) can not be controlled by manufacturers tolerances and as such have to use a lot of negative feedback to negate the whopping amounts of distortion that they create. But, they are CHEAP! So, to the uneducated consumer these devices look like the deal of the century! Wow, a thousand watts of power for $299! Smoke and mirrors people! Any specification can be fudged to make it seem to the consumer that the laws of inflation and economics does not apply to the consumer electronics industry! How much did that Volkswagen Golf cost 15 years ago versus today… you get my drift.
Now, there have been a lot of developments in manufacturing that have reduced the costs of making an amplifier today. Things like computer controlled design and manufacturing (CADCAM) have vastly reduced the assembly line costs of all companies and this has also helped the fit and finish of these products but not to the degree that some of the manufacturers are asking you to believe!
So, in a nutshell, when you are looking for a good sounding surround sound system get one with discrete transistors and you will be well on your way to a longer lasting and better sounding system or give us a shout and we will make sure you do!