ski bum
|
If you're considering a two watt amp, it makes sense to determine it's maximum capabilities and assess if it is enough to meet one's expectations. This should be illustrative, let's do a little thought experiment using a two watt zen amp.
Ok, so I come home from work or a hard day on the slopes, kick of my sneakers and cue up some music. Say it's something with rather wide dynamic range, e.g. Ravel's Bolero. Now, if you're the type with too much time on your hands, you can run the file (assuming it's digital) through an editing program to determine relative levels of the music, including the average level and any peaks. If you're lazy, you can simply look this up in the dynamic range database. I'm a big fan of the DR database.
So my particular recording of Bolero has 20 db of dynamic range (an extreme case). Now, given my speakers sensitivity of 95.5 db/w (measured, genuine sensitivity, not some inflated manufacturer spec), in my small room, and with corner placement, plugging that info into the calculator indicates I can get ~98 db at the listening position. So two watts equals 98 db, the peak or maximum output the amp can deliver to me at my chair. The question at that point is, "Is this enough?"
Applying that to my Bolero listening session and working backwards from the peaks on the program material, it means I can listen at average levels of 78 db and have adequate headroom to hit the peaks cleanly.
If I play RHCP or something horribly compressed, the dynamic range is probably a paltry 5 db or so, I can listen at an average level of 93 db and still have enough amp headroom to cover the peaks in the recording. The recording itself may sound like arse, but that's another story, this is just to demonstrate required power for dynamic peaks in the music.
That's about it when considering power as the sole consideration. But of course, the subject of this little thought experiment being a tube amp, it gets even more complicated.
Back to Bolero, if I listen at average levels above 78 db, those times when the recording calls for an extra 20 db exceed the amp's limits and the amp clips. These amps are characterized by a low order, monotonic pattern of harmonics when over-driven. Within the early stages of being over-driven/clipped, this sort of distortion pattern tends to slip right by the ear. As it increases it tends to act as an ideal compressor (the amps electrical output plateaus out, but the harmonics within that envelope increase, adding bite/edge/presence and which is perceived as subjective loudness...this is largely responsible for the 'tube watts are more powerful' meme). In this case, and provided I don't drive the amp into gross/excessive clipping, which sounds bad any way you slice it, I can push the average levels considerably higher; the peaks are clipped, but not objectionably so. Is it any wonder these amps seem to bring out the low level details in recordings so well? When run slightly in the red, they literally do bring all that low level info up in the mix, while not causing objectionable distortion on the clipped peaks.
Now, lets move the rig into a larger room, with more space to fill and greater distances. In this more demanding situation two watts becomes a severe limit. Peak capability will only get me to ~93 db at my chair. Still fairly loud, but not soul stirring loud. Not enough for "correctness" or "authority" -in the terms you asked through my interpretation. Much easier to drive the amp to gross clipping in this case. The answer? More sensitive speakers, or more power. That would go for the small room situation if 98 db peak output was unsatisfactory.
In my own case, I generally listen at average levels of 85 db or so, and like rock, blues, jazz. Typically, on a good recording, such music has a dynamic range of 10-15 db, so two watts in the small room mentioned above is right on the margins but acceptable, and inadequate in the larger room.
Does this help?
|