Hi All
I think a number of issues are linked in here.
First amplifiers, unlike loudspeakers, have a subtle effect on sound. Blind tests show that by and large amplifiers with low distortion and not driven to clipping or driving hard loads etc sound pretty much the same:
http://www.stereophile.com/features/113/index.htmlThis has led some people like Tom Nousaine and Arny Krueger to proclaim amplifier differences beyond low distortion etc are irrelevant and those that disagree are of the weirdo tweako brigade. That is one extreme. However those that hold to such views ignore that experienced listeners, in blind listening tests, can pick the differences between amplifiers. Indeed they can pick the difference between the even more subtle effects of cables. It is precisely those highly critical listeners that audiophile manufacturers cater to.
When I started out in Hi Fi all those years ago one thing I learnt quickly is that constructing audiophile quality flea powered amps is a doddle - it can be done relatively cheaply. Constructing high power ones is much harder and much more expensive eg the cost of power supplies rises dramatically. Amplifier costs have come down so that good quality (not great but good quality) high power amplification is now available at low cost (eg the 200w Behringer A500 for $180.00 street price). Such products measure beautifully but to critical audiophile ears are lacking. And that is one of the issues - to go beyond what measurements show we must actually listen and introduce an element of subjectivity. When that is done then what constitutes your preference will vary. For some what they are seeking is ultra low noise and extreme detail retrieval. Battery powered flea powered amps provide that without breaking a sweat. For others it is ridiculously low distortion - for those audiophiles class A designs appeal - and low power designs are much easier to construct for that.
http://www.siliconchip.com.au/cms/A_102474/article.html And yes trained ears can hear such low distortion. Leo Simpson, a well known electronic magazine writer, published an ultra low distortion class A amplifier some years back and was surprised that it sounded a good deal cleaner than conventional class A/B designs. But achieving such low distortion can only be done with lots of feedback which has its own issues. This leads still others to zero feedback class A valve designs and its 'musical' distortion some prefer. The list is endless. The point is it is much easer and less costly to meet those requirements in low power amps.
Of course going that route has its own problems - engineering is always about compromises. One can not drive low efficiency speakers to high volume levels with low power. Those that install systems for a living say that people rarely if ever go beyond about 110 db peak at the speakers. For relatively low efficiency speakers of 85db this equates to peak power of over 200 watts. Increase the efficiency to 96db and power in now a more modest 20w. 110db is really loud - so it is fortunate it is just a peak. CD's are recorded with about 18db headroom so this would equates to 91 db average produced at the speakers or at usual listening positions of 3 meters about 81 db. That is for mono - for stereo it would be 84db. Power mowers produce levels like that (a hair drier and person shouting produces about 80db). Would you like a power mower next to your ears in your listening position at home? Would you even like a hair dryer? How would your neighbors react? Indeed prolonged exposure at 85 db or greater can cause damage to ears:
http://hearing-protection.4ursafety.com/exposure-limits.htmlThis leads some like myself to never actually exceed 82db average at about 1 meter from speakers ie a little above the level of someone shouting about one meter from the speaker. This still allows the reproduction of peaks at about 100 db which is very loud - for chorus and orchestra in a concert hall peak levels can reach 105db so you are not missing out on much realism. But rock music is another matter - levels at rock concerts can easily exceed 120db. To realistically reproduce that you need power - and heaps of it. Just watch your ears and neighbors complaining. But getting back to the more sensible 82 db at 1 meter consider 85 db sensitive speakers. Allowing for 18db headroom this gives a max of 100 db max (instead of the 110 max you had before - which only sounds half as loud BTW) you now only need a more modest 20 watts. Raise the sensitivity to 90 db and you only need about 8 watts. Raise it to 96 db and you need less than a puny 2 watts.
Dave Ellis also has some rather interesting facts about amplifier power:
http://www.ellisaudio.com/wattsratings.htmSo just to bring it all together:
Cheap amplifier power is now available to satisfy all but critical audiophiles. The A500 Behringer for example will easily drive even relatively inefficient speakers to the maximum spl levels experience has shown is rarely exceeded.
However those amplifiers lack when listened to critically by audiophiles.
It is simpler and cheaper to build low power amplifiers that meet audiophile criteria.
Listening at sane levels to moderately efficient speakers requires less power than you think eg for 90db speakers you can easily get by with 8 watts.
And once one breaks away from heaps of power than some truly excellent amplifiers can be had rather cheap
http://www.audiocircle.com/index.php?topic=15411&sid=8c9bf6f5e3b76d6cac69cfe2926452a3 Thanks
Bill
