Stereophile - MF Supercharger article-add 550W/ch.
Along the same lines, check out the 6Moons review of Nelson Pass's First Watt F4 current drive amplifier. 50wpc stereo, 110wpc balanced monoblocks. Although, the design can easily be scaled up or down from that output. In the review, Srajan runs a couple of SET amplifiers into the F4 and compares the sound with the SET's/F4 on their own. |
Hi Dbphd, the way that tubes operate closer to the rules of human hearing is through the lack of odd-ordered harmonics, which comes from greater linearity and less need for feedback. Feedback runs counter to the rules of human hearing (i.e. adds high order odd harmonics). Human hearing uses high-order odd harmonics as a way to measure loudness. Our ears are so sensitive to these harmonics that fractions of a percent is easily audible. We hear them as a 'sheen', 'hardness', 'clinical', 'brittle' or 'chalky' quality in the reproduction. |
I haven't published in nor even looked at JASA for several decades, so I am far from current. But evolution of the human auditory system occurs very slowly, over thousands of years. You have to ask yourslef why human hearing, a system evolved for avoidance of danger and communication, would be sensitive to high-order harmonics. What might the teleological explanation be for developing such sensitivity be? For example, we can explain interaural sensitivity to timing and level in the lower frequency range as providing localization cues that could be important for survival. But what value might high-order harmonics add to our lives? db |
Hi db, I don't think high-ordered odd harmonics do add to our lives. The current state of high-end audio suggests that they don't. Their rarity in nature might mean that less brain power is required to detect the change in volume, but what is important is not the 'why?' but the fact of 'what is'. That we react this way is easy to demonstrate BTW. If you have access to test equipment, set up a sine wave and run it through an amplifier at 0VU and listen to the result. Now run down the volume, switch to square wave, and turn it up until you get the same perceived volume level. Now look at the meter- you will be about 20-24db down compared to the original sine wave. That's 1/100th the level or so depending on your perception. If you add a filter to filter out the lower orders, you will find there is almost no change in perception. |
Atmasphere, A good empiricist needs first assure an absence of artifacts in such a demonstration. The signal generator and transducer can be sources of spurious acoustics, especially with square waves. A fast scope can monitor a generator, but I don't know how to monitor a transducer to assure absence of artifacts. db |
