Axiom Home Page Forums General Discussion Technical Questions Amplifier - General Information Request

OK...I'll be a goat and jump into this tar pit. There is a huge difference in the sound of amplification. I used to be a firm believer that electronics all sound the same. I agreed with what Julian Hirsch used to preach; Solid state amplification, if created with low harmonic distortion and noise figures and a flat frequency response, will all sound the same.

I have changed my mind over the last several years. While the theory is completely correct, I have come to the conclusion that in practice, amps are not CREATED the same. My 1986 NAD reciever put out 75 watts per channel and sounded bigger and fuller, with less strain, than many of today's 100X5 receivers. I have recently (a few years ago) upgraded to an Outlaw 950 and a Parasound HCA-855a 85X5 amp. I bought the amp before the Outlaw 950. I hooked the amp up to the NAD, and the Parasound added more depth and precision to the soundstage, as well as better bass. (and my NAD was quite good!) While the main specs (response, THD, and noise) may be comparable, and published WPC may be the same, real world power may be completely different. A 100X5 Sony reciever may have good published specs, but in real life may strain or even clip before reaching outputs that my 85X5 Parasound can achieve.

Not only must real power be taken into consideration (usually tested with a resister of known CONSTANT value), but we must also take the speaker into consideration. A speaker is not an 8 ohm resistor. While it may be considered to be nominally 8 ohms, in real life it may range from 2 or 3 ohms to 40 or more ohms depending on frequency. An amplifier's ability to handle these difficult loads may be what leads to differences in overall sound.

The M80 has been referred to as an "easy" 4 ohms. Many people have come here asking if brand "X" amp or receiver can drive the M80s. The truth is, if they can't, they will sound very different than an amp that can drive them successfully. More important than WPC is amperage output. Higher amperage output (higher current) allows 4 ohm speakers to be driven more easily.

Getting back to the M80's "easy 4 ohms". It is nominally a 4 ohm speaker because it hovers between 3.5 and 5 ohms through a good majority of its frequency range. On the other hand, the Paradigm Reference 100's are a more difficult speaker to drive. Although they have much of their response frequency's resistance well above 6 and 8 ohms, they dip down into the nearly 2 ohm range in spots. This complex resistance can cause lesser amps to cook if loud music is played in these frequency ranges! (or drive the amp into clipping, cooking the speakers instead).

What I am trying to say, is that all amps may be equal in driving a constant resistive load, real world interaction between amplifier and speaker can and does indeed lead to differences in how actual sound is output from the speakers. While published output wattage, THD, and noise figures may be compararable or even equal, differences in the ability to deliver high current and handle difficult reactive loads is what I believe makes amps sound different.

(these thoughts are mine and mine alone and do not neccessarily represent the truth. all opposing views are welcome, but food and beverage throwing, deficating, hysterical laughing, or pointing and screaming will be taken personally)

Differences in power vs power rating and such that you mentioned are what I, personally, would accept as things that would change the sound of an amp. However, I just have my doubts that well designed (ie, not Sony 5x100 BS amps) should sound the same at the same volume levels. If the amps are equally capable of driving the load of the speaker, they should sound the same.

Baah.

I've a burning desire to learn what the NRC has found, regarding amplifier neutrality. How much of their results are public, or is it more of an empty lab where companies can test things at?