Κώστας Φ.
Truth hurts. Here's a teddy bear.
- Μηνύματα
- 8.978
- Reaction score
- 894
The Aurora: built by Gary Dahl, current sources by Gary Pimm, metalwork by Josh Stippich, rosewood chassis by Phil Bruckbauer, and circuit design by Lynn Olson.
"...
As a loudspeaker designer, I knew all too well that expecting speakers to be resistive was a vain hope - in fact, the best speakers are typically the most reactive and hardest to drive! I wasn't willing to cherry-pick speakers that were "SE-friendly" - to me, that's another way of saying "speaker-unfriendly." Speakers, by their nature as electromechanical transducers, are not just reactive, but store resonant energy for tens of milliseconds and transmit it back to the amplifier - and all speakers do that, electrostatic, planar, horn, single or multiple-driver. Speaker drivers are intrinsically resonant.
Thinking along these lines - an amplifier that remains linear when driving a complex, nonlinear, and poorly-defined load - leads to Class A PP, preferably with direct-heated triodes instead of triode-connected pentodes. (Tests in Vacuum Tube Valley magazine shows DHTs have about one-half to one-third the distortion of triode-connected pentodes, not a small difference.) The reason is clear when you look at the composite curves of Class A PP triodes: the grid-lines are essentially straight and parallel, so when the load-line opens into an ellipse (becomes reactive) there is no change in distortion.
BY contrast, all other other circuits and devices ... SE, or PP with Class AB, or pentodes, transistors, MOSFETs, etc. all have grid-lines that are curved. Class AB pentode (or transistor) is the worst, with high curvatures centered around the zero-signal region. In others words, the first watt is the worst watt ... but it only appears with reactive loads! Unfortunately, speakers are reactive: they can't help it, they're bandpass filters, and they also store energy for relatively long periods of time (milliseconds) and reflect it back to the amplifier. With most amplifiers, the reactive and delayed energy from the speaker driver greatly increases the amplifier distortion. This is why amplifiers can sound so different with different speakers.
With SE, the overall curvature of the grid-lines is still there, but is quite mild in the zero-signal region; the first watt really is the best watt. This is a critical point; music spends most of the time at low levels, with brief peaks that jump to 10 to 14 dB above the average. On a statistical basis, the greatest percentage of the time is in the 1-watt or lower region, at least if the speaker has any kind of reasonable efficiency.
But ... if you want linearity at low and high levels, near-total immunity from reactive loads, only PP triodes operating in very deep Class A can deliver straight and nearly parallel grid lines.
..."
Διαβάστε περισσότερα: nutshellhifi.com
Νόμιζα ο Olson ασχολείται μόνο με ηχεία! :crazy_1:
Όπως και να'χει, ενδιαφέρον άρθρο....
