Amplifier power question

[RayDunzl]

That’s beautiful, Ray. I always did like graphs better than equations.
When you look at the scale on the left (y axis labels), is each increment 1dB?

The left scale is Watts, the divisions are multiples of 10, which would correspond to increments of 10dB (I think).

It shows relative, not absolute levels, because this is not calibrated to any particular voltage, but might give an idea of the ranges involved when a signal is played.

 

[RayDunzl]

Should that read “decreasing sensitivity, increasing output power?”

I think the word "sensitvity" is a poor choice given how it is used.

For audio, it is defined as something like "the maximum signal the amplifier can accept that will not cause the output to be clipped"

But all three amps are equally "sensitive" to equal input levels. 1V input will become 20.89 volts at the output for all three, because all three have 26.4dB gain.

But, the bigger amps will take a higher ultimate input voltage, and yield an ultimate higher output voltage, before they "clip".

 

[RayDunzl]

I have a naive question though. What is “reference” level and who, how, and why they came up with that? Is it what the sound engineer sets in a recording studio? Just curious.

The real answer may be discussed above, an often quoted 83dB average is the "reference" I was referring to, as I remember, a suggested preferred level for the folks mixing and mastering to use.

Anyway, I find that level, when measuring/calibrating to be loud, but not too loud. It doesn't excite ringing ears after extended listening. Call it "comfortably loud".

83dB long term average, with up to 103dB peak readings (usually not more or occasionally less, depending). It's in the "flatter" area of your hearing, if using the old Fletcher Munson curves.



The reading displayed on the SPL meter was 84.9 average and 101,2 peak.

 

[Tom C]

Thanks Ray.