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Sound Quality Vs. Measurements
Sound Quality Vs. Measurements
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Old 26th December 2011, 05:34 PM   #181
a.wayne is offline a.wayne  United States
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Originally Posted by john curl View Post
Pano, you only have 1/2 the story. Class A is not necessarily the most thermally stable operating condition. It can be shown that heavy Class AB-1 is as good or better, if you go back to the root equations. However, thermal stability, both transient and long term is really important, and real designers make sure that the THERMAL CAPACITANCE is very high by close mounting the output devices on good insulators (if necessary) properly torqued down and used with thermal grease on a substantial heatsink . This removes most of the short term gain changes due to temperature.
High input stage operating current, using only a part of the class A portion can also be helpful.
Interesting John , could you elaborate more on your previous comment about toroid transformer vs a super-quality EI or R core transformer.
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Old 26th December 2011, 05:42 PM   #182
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Old 26th December 2011, 05:47 PM   #183
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In truth, the JC-1 should outperform the Ayre on difficult loads, but apparently it does not always, even with very large electrostatic speakers. This was one of my first 'upsets'.
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Old 26th December 2011, 06:18 PM   #184
Wavebourn is offline Wavebourn  United States
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Sound Quality Vs. Measurements
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Originally Posted by Pano View Post
Sure, SY. But there might be in typical tube amps.
Sure, like a cat does not need to run before jumping on a fence, tube amp does not need to have such low THD and DF to sound nice. However, my Pyramids have lots of feedbacks, stabilized voltages, and they show comparable with transistor amps DF and THD. I designed them to drive high-end line arrays, but as far as I know all prototypes I made drive Maggies and speakers with crossovers meant to be driven by SS amps.

I.e. you can design and build tube amps with low THD and high DF, but nobody actually needs it. Especially those who drive full-range high efficiency speakers. That's why you don't see so many tube amps with extremely good parameters that are not actually needed. Especially, when they lead to horrible transients on overload, in all amps, no matter made they on diamonds, or on steam engines.
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Old 26th December 2011, 06:24 PM   #185
Wavebourn is offline Wavebourn  United States
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Sound Quality Vs. Measurements
Quote:
Originally Posted by john curl View Post
Pano, you only have 1/2 the story. Class A is not necessarily the most thermally stable operating condition. It can be shown that heavy Class AB-1 is as good or better, if you go back to the root equations.
John; it is true only for biased in class A complementary followers. My amps that have bootstrapped source follower loaded on counter-modulated current source mean totally different story: power dissipation varies with variation of load impedance only, not with the signal.
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Old 26th December 2011, 06:31 PM   #186
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The problem for of the toroid power transformer is that it has too much bandwidth due to the high cap coupling between input and output windings.
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Old 26th December 2011, 06:34 PM   #187
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Well, Wavebourn, that does not completely take you 'off the hook', then?
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Old 26th December 2011, 06:42 PM   #188
Wavebourn is offline Wavebourn  United States
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Well, Wavebourn, that does not completely take you 'off the hook', then?
It is not about hooks, John; it is about class A amps and heat - aided distortions.

Edit: I am going to spend some money on silicone carbide devices, to try if some difference will be heard or not...
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Last edited by Wavebourn; 26th December 2011 at 06:53 PM.
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Old 26th December 2011, 07:01 PM   #189
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'off the hook' means: Out of potential trouble. Sorry, there are many other meanings as well.
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Old 26th December 2011, 07:18 PM   #190
Wavebourn is offline Wavebourn  United States
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'off the hook' means: Out of potential trouble. Sorry, there are many other meanings as well.
Potential troubles are always here, when we register mechanical waves by electricity, and reproduce them by electricity. Microphone preamps and power amps are always bottlenecks.
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