No, there's no 'extra power' as all an amplifier does is to provide volts from a low impedance source. If you're taking X volts from an amplifier to generate a certain loudness, the loudspeakers don't 'know' there's any more volts available. Provided that a low power amplifier has a low enough output impedance and can provide enough current for whatever load your loudspeakers present then unless you run out of volts, there will be no difference between a low power and a high power amplifier.
If the lower power amp (met impedance and current requirements and) could provide the same X volts as the high power amp so it's 'extra power' was redundant and this gave the desired loudness would the input sensitivity be the main factor in choosing between the amps (assuming similar price)? Say the source was CD standard 2 volts and the high power amp had gain of 26dB with input sensitivity of 1.6v whilst the low power amp was 28.6dB/0.6v.
In your example the 28.6 db amp would have less power if its input sensitivity were that low. In fact it would be only about 25% as powerful. If the lower power amp is powerful enough, it really wouldn't matter about the input sensitivity. In fact if your source is capable of 2 volts you'd just be more likely to clip the lower powered amp. But used with care either would do.
Amplifier sensitivity and gain are really two different calculations although closely related. Sensitivity tells you how many volts it takes to drive that amplifier to maximum power, whatever that power might be. Gain tells you how many volts you'll get out for a certain input, whatever that input might be.
Thanks much!! This one graph answers many questions that hi-fi dealers cant answer. Visual representations are always easier for me to quickly understand.
Thank you. Time to take the plunge and, in the spirit of learning, expose my ignorance to some public scrutiny
Yes (25% less powerful) as max voltage output is 16 Vrms compared to higher power amp's 33 Vrms. With the higher power amp the gain (or should that be input senstivity?) controls are set below mid-point to get desired loudness with volume control at 80% -90% rotation for the majority of music played. I've not measured the output voltage but it must be no more than 16 Vrms or perhaps even less. So I'm estimating that the lower power amp is powerful enough for my 'speakers/room - though 'speaker manufacturer rating is 28.3V/100 watts. Based on that logic the higher power amp has lots of 'extra power' which I don't seem to need (for recordings at normal levels) but opting for the lower powered amp I run into potential problems due to its high input senstivity (relative to 2 V source). That prompted my question about input senstivity becoming the deciding factor. Can this be sorted by attenuators (-6dB?) on the lower power amp's inputs to reduce input sensitivity sufficiently whilst ensuring that max available output voltage doesn't fall too much below 16Vrms? Or is the higher power amp with unused 'extra power' the better option despite the risk of dials being turned up too high accidentally?
You could use attenuators if it is a problem. There even in line devices like this:
That’s beautiful, Ray. I always did like graphs better than equations.
There are a number of "reference" levels, depending on what you are listening to and how (stereo, surround, headphones). Bob Katz has done a lot of work on this and some of his articles are online (I think chapter 8 in his book deals with it).
