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Old 8th May 2013, 07:17 PM   #2961
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>I believe that JC is correct, because there loss of Slew Rate using output inductor.
Huh?
I can't believe that JC has said this.

Cheers,
E.
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Old 8th May 2013, 07:31 PM   #2962
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I don't need output inductors in any of my power amplifiers. I cannot say that SOME load, probably pretty exotic, might cause trouble, but not in normal operation, to the best of our experience with 1000's of Parasound amps out there, over the last 20+ years.
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Old 8th May 2013, 07:33 PM   #2963
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Quote:
Originally Posted by Edmond Stuart View Post
>I believe that JC is correct, because there loss of Slew Rate using output inductor.
Huh?
I can't believe that JC has said this.

Cheers,
E.
I said the loss Slew Rate, JC according to the account of an enthusiast, said that sound is better without the output inductor.
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Old 8th May 2013, 08:02 PM   #2964
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An output inductor does NOT affect the slew rate. It only affects the rise and fall time, being something else than slew rate.

Cheers,
E,
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Old 8th May 2013, 08:19 PM   #2965
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Quote:
Originally Posted by Edmond Stuart View Post
An output inductor does NOT affect the slew rate. It only affects the rise and fall time, being something else than slew rate.

Cheers,
E,
I always calculate the Slew Rate for rise time, the output inductor reduces mainly the rise time resulting in damped square wave.
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Old 8th May 2013, 08:22 PM   #2966
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Rafael L, I know that you mean well, but it is not 'slew rate' specifically that makes such a difference. In fact, I cannot tell you, precisely WHY significantly reducing the inductance of, or actually removing the output inductor actually makes a difference, BUT IT DOES!
What I was shown, actually by the engineers at Parasound, in Taiwan, that output conductors could be removed, in a PRACTICAL amplifier and virtually no harm would be done, BUT you would actually potentially improve the ultimate sound quality, and you could REDUCE the high frequency output impedance. Worth the effort.
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Old 8th May 2013, 08:38 PM   #2967
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Quote:
Originally Posted by Rafael L View Post
Hi Bob

Unless I'm mistaken was John Curl who brought this claim. I believe that JC is correct, because there loss of Slew Rate using output inductor. You should know that Ex: one amplifier with 50V/us can only have 25V/us with output inductor. The loss of Slew Rate (resolution) is audible because it has compression of analog audio.
Another issue, many amplifiers are stable in "born" but not with 2m cable (practically a pure inductor 2uH) with a capacitive load R//C.
Hi Rafael,

The presence of an output inductor does not generally limit slew rate. My MOSFET power amplifier with error correction had an output inductor and it had a slew rate of 300V/us.

A claim that the output inductor can limit slew rate can easily be disproved by SPICE simulation. We are not talking about big inductors.

Cheers,
Bob
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Old 8th May 2013, 08:48 PM   #2968
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The output inductor is just like a low pass filter. If you do it right, it could reduce THD at high frequency (e.g. reduce THD @ 20KHz). You don't need your amplifier to output ultrasound.
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Old 8th May 2013, 09:15 PM   #2969
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Originally Posted by jxdking View Post
You don't need your amplifier to output ultrasound.
Why not? Audio amplifier is not a simple function generator, musical signal is much more complex than a sine wave.

Some simulations:

No output inductor : Rise time 1,54 u/s - 40V/us
With output inductor(1u//1R): Rise time 1,98 u/s - 30V/us (node inductor - load)
With output inductor(1u//1R) + cable 2u: Rise time 2,36 u/s - 26V/us (node cable - load)

I should not be talking about anything new, loss of resolution in music (program material) is well known problem in recording studio (compression).
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Old 8th May 2013, 09:21 PM   #2970
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Originally Posted by john curl View Post
I don't need output inductors in any of my power amplifiers. I cannot say that SOME load, probably pretty exotic, might cause trouble, but not in normal operation, to the best of our experience with 1000's of Parasound amps out there, over the last 20+ years.
You could spend a few more details:

You use an RC filter on input?
You test the stability of their projects, with load//capacitive more meters of cable?
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