gsrai wrote:
GentsMy house resembles a power house at the moment as I have an MF X-AS100, MF A% and Sugden Bijou apmaster poweramps lying around to test.
As expected, the A5 power is better than the other 2 with the clearest difference being the spaciousness of the sound and ease with which it flows
only problem is it is a bit of an ugly looking beastie
On to the other 2, The Sugden baby really surprised me as I can't really tell the difference between this 35w and the 100+W X-AS100. I've read around the design (dont understand it) so how come the little Sugden is able to drive my hard to drive PMC GB1's (I always thoguht the strong point of MF was the current drive and I know the Sugden isn't class A).
Does anyone understand why less WATTS at relatively low volume sounds similar - I'm confused :?and cal somebody also tell MF to but the big powerhose A5 in a small package so I can keep it :Upset:
In the past, I gave these kind of questions a lot of thought, and a bit of research, and I think I understand it, but anyone, feel free to correct me...
Amplifer power
You need 10 times the power to double the volume, so the difference between a 35 watt amp and a 100 watt amp is not as much as the figures might suggest.
Amplifier gain
That is, the step up between the input to the power amp (or power amp section of an integrated amp) and its output to the speakers. This is a constant for any given amp, and normally quite similar between different amps. It is not related to the power output. A 20W amp and a 200W amp (especially from the same manufacturer) may well have identical gain. The volume of the system is controlled by the level of the input to the power amp (section), i.e. the level of the output from the pre-amp (section).
The difference between the 20W amp and 200W amp will be the level at which they run out of steam - i.e. the level at which the amplifier's gain, when applied to the input signal, will result in the amp being asked to output levels in excess of its power rating. One consequence of this is that it is perfectly possible to bi-amp with two amps of identical gain, even though one is much more powerful than the other, as long as the weaker amp is not asked to deliver more power than it is able to.
Input sensitivity
Most modern sources (I'd say all digital ones, and even many phono stages) deliver an input voltage far greater than that needed by the amplifier to deliver its maximum output. For example, my Arcam A85 has an input sensitivity of 250 millivolts, which means that in order to deliver its rated output of 85 watts, it needs an input signal of 250 millivolts. The Compact Disc specification is 2 volt max output (ie input to the amp), and many CD players deliver even more. So in my case, my CD player is delivering at least 8 times the voltage my amp needs for maximum output (at least during the loudest passages of music). The upshot of this is that when playing a modern source, most amps will enter clipping, distortion and general amp-and-speaker-frying nastiness, long before the volume is up to maximum. As a general rule, at about 12 or 1 o'clock on the volume control, most amps are delivering as much clean power as they are able to.
Listening
So, if most amps have somewhat similar gain and input sensitivity, and vaguely linear volume controls (as I believe to be the case for mainstream hifi amplifiers), the volume they deliver for a given position of the volume control will be similar. You'll really only notice the difference in power output at headbanging levels with most rock and pop music. With classical music, the dynamic range of the recording is much greater. With the volume control set so you can just about hear softly plucked violin strings above the background noise of the central heating boiler, traffic, the kids, the dog, etc, etc, a low power amp driving insensitive speakers will give up the ghost when the timpani and brass come in at full pelt (I listen a lot to Lizst, whose music contains occasionally insane dynamic contrasts). Which is why a strong, powerful amp is a good thing, despite all of the above.