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In Reply to: RE: I would say nearly all amplifier designs are conceptually WRONG! posted by morricab on September 18, 2015 at 01:11:19
Morri,
Whats the short list based on your spread sheet ..
Follow Ups:
I happen to be convinced that overall amps without NFB sound more real, whatever that really means. But there really are trade offs. Static distortion certainly goes down. Frequency response certainly is better without the interaction of the speaker load and the high output impedance of an NFRB amp. And to add one more the bass is better controlled in an NFB amp. It's sort of like two people getting 90s in the same exam. But both missed completely different questions. Does that mean they both have the same amount of knowledge about the test subject?
A properly designed SET has frequency extension well above hearing and bass well below 20Hz that is powerful and controlled. The lack of control is largely due to Saturation of undersized or poorly made OPTs. Conceptually there is no reason for either issue it is purely execution issues.
With ant transformer amp it's difficult to get a low enough output impedance for either flat response with a reactive load or good bass control unless so much negative feedback is used that the amp would end up unstable. There's no other way around this for either SE or PP tube amps. It's the nature of tubes and output transformers no matter what the deatils of construction. This doesn't make a normal tube amp useless just flawed, that is colored, in ways some like and others don't like. You pick your sound color.
As long as the damping factor is > 5 there are not significant variations with most speakers. Some SETs even manage this. Even so, the variation is less than the speaker will have intrinsically. This means you are adding a bit more variation in the FR of an already non-flat device...big deal.
A damping factor of 5 is significant with differences of over a dB or so unless the speaker impedance curve is very flat and that is a rarity indeed. Try at least 20 and there are still small variations which will subtly color the sound, not so much as overt colorations but sense of distance, openness, even detail depending on how wide and where the dips and bumps are.
my lightly modified 1960s Mc 275s.
Jeremy
WHat is 1db (+- 0.9db to be more precise) when most speakers are at best +-3db in a typical room (usually much worse than that)?
http://www.audioholics.com/audio-amplifier/damping-factor-effects-on-system-response/damping-factor-effects-on-system-response-page-2
And compromise means that ultimately, we each evaluate the strengths and weakness and choose a product that suits our individual preferences. And clearly these personal preferences vary. In the end, when amp performance reaches a certain level, there is no "best", there are only different amps for different compromises.
try it! you know you want to!
Nothing is perfect or "best" in every situation. It comes down to tradeoffs. How those tradeoffs are ordered is entirely personal preference.
try it! you know you want to!
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