The neatest description I have read for an amplifier is the one by the late Peter Walker, founder of Quad - straight wire with gain. This one admirably states that all an amplifier is supposed to do is amplify the strength of the signal, without either adding or taking away anything from it in any other respect.
When it comes to speakers, it is far from a solved problem. A speaker is also an electro mechanical device, with many different material usage possibilities, unlike solid state amplifiers. Designing speakers has many degrees of freedom for the designer, and the ability to voice the speaker in distinctively different ways. The amplifier problem on the other hand has been solved decades ago, as far as 2 channel solid state amplification is concerned.
Look at the definition again - it says that an amplifier is not supposed to have a sonic signature.
The position that is taken by people like me is often misunderstood/misquoted by audiophiles to say that we think that all amplifiers sound the same.
Whereas the position I support says that in a level matched blind AB test, it is not possible to distinguish between two amplifiers, both of which are operating within their design limits.
To explain this, let me turn to something called clipping.
Most people think that an amplifier pushes out power to speakers. This isn't the case. Speakers pull power from an amplifier, which, subject to the volume control setting, supplies it as demanded. Remember too that a speaker connected to an amp terminal is a closed loop - almost a short circuit, with the speaker coil in place. The resistance of the speaker/speaker coil is what is the speaker impedance and what stops it from being a true short circuit. But this resistance, about 8 ohms, is very small. And the power/current that the speakers draw from the amp depends on the frequency of the music that the speaker has to reproduce, with lower frequencies resulting in a higher power draw. In poorly designed speakers, this can also result in a dropping of the impedance to close to zero, in the 1-2 ohms region, compounding the power draw increase. When this happens, the speakers can demand more power than the amp can supply, leading to distortion in the signal wave form causing clipping to it, which is audible as distortion. This distortion is not necessarily unpleasant, sometimes it is this that gives the so called warmth to the music. Beyond a point, it can damage the speaker, which is why there is a greater risk of speaker damage from low powered amps, and not ones with higher power than even the speaker specs recommend. For higher powered amps as long as the volume control is used carefully, because it is the speakers that are in control of the power draw, they don't get damaged.
But coming back to clipping induced audible distortion - it may sound good, but it isn't hifi. High fidelity means that nothing is added or taken away from the characteristics of the recorded signal.
But when clipping isn't happening - that is to say when the amp is working within its designed limits - that is when the amp is not distinguishable for any other statement holds good, as long as sound levels are within 0.2 db of each other.
What then should decide the purchase of an amplifier?
My views:
1. Enough power to do the job, defined by the speaker needs, plus something more as a power reserve. For a very large majority of applications at home, 60-80 wpc is enough. Even 100wpc, solid state amplifier watts aren't very expensive now.
2. Features such as input/output sockets, USB sockets, etc., based on individual needs.
3. Availability of parts and after sales service
4. Brand reputation for reliability
5. Tone controls - another thing isn't hard to implement without, as some think it does, "corrupting" the signal chain. The ability to tweak bass and treble levels is invaluable in customising the sound of a speaker to the room acoustics/environment.
6. Integrated amps are as good as any. With solid state designs and properly implemented power supplies, the preamp separation to protect the delicate low voltage signal at the preamp stage from distortion causing effects isn't as important any more, where the power outputs are in the ranges mentioned above.
7. Footprint criteria
Sonic signature doesn't figure any where in this list.
Amplifiers from even the budget end of reputed makes such as Marantz, Rotel, NAD, Cambridge Audio to name just a few, meet many of these criteria quite easily. I am partial to Quad for long term use, but that is because their amps are built from non special parts and their UK service is legendary - even today one can ship a 40 year old amp to them and they will bring it to perfect working condition. But I have never had any problem with any of my solid state amps, ever. And I have bought some without having heard them first. Never a cause for regret, except when I realised it hadn't made a damn difference to what I was hearing!
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hyeah:
:yahoo:
