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Crossover Distortion, the truth
Crossover Distortion, the truth
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Old 15th December 2017, 08:26 AM   #61
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The "Krill" is an/any multistage complementary-parts-pp-design? It sounds horrible, with or without crossover distortions, whateverC-:
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Old 15th December 2017, 10:02 AM   #62
RNMarsh is offline RNMarsh  United States
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Crossover Distortion, the truth
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Originally Posted by scott wurcer View Post
But in a larger sense none of these circuits like NP's stasis, Hawksford, and other error correction schemes have much of a presence in current DIY. Many folks are perfectly happy with a Self blameless with modern devices.
I very much agree.

I have promoted this for a long time. especially when trying to get ultra low distortion at all freqs and levels.

Damir (DIY) took up the challenge and his circuit uses EC and CFA and has my complete "wish list" of performance.

It was also suggested as solution for test equipment needing ultra low distortion.

It just seems the practical way to go and once a few more people do it, might become mainstream.


THx-RNMarsh

Last edited by RNMarsh; 15th December 2017 at 10:05 AM.
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Old 15th December 2017, 11:24 AM   #63
dadod is offline dadod  Croatia
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Sorry Richard, just small correction. I have designed some power amps with EC, but this one does not use it. It uses unique compensation, I called it OITPC (Output Inclusive Two Pole Compensation). It is TPC but with two input legs, one capacitor connected to the VAS output, other one connected directly to the output. In this way I was able to get more than 80 dB of Loop Gain (feedback) at 20 kHz and ULGF moved behind 3 to 4 MHz.
In this way THD was even better than if I used EC (EC complicates the compensation).
I may opinion if one wants to design non global NFB amp then EC is needed.
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Old 15th December 2017, 12:49 PM   #64
scott wurcer is offline scott wurcer  United States
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I may opinion if one wants to design non global NFB amp then EC is needed.
Damir
That was my impression essentially gobs of feedback. An EC output outside the global feedback is an interesting exercise but it would be difficult to expect ppm distortions everywhere. Once you're past -80-90db low order across the board my opinion remains that no compelling evidence has been presented that the distortions alone have any bearing on the sound.

BTW it's hard to make a general purpose amplifier (robust against difficult loads at any closed-loop gain) with output included compensation, but they do exist.
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Last edited by scott wurcer; 15th December 2017 at 12:52 PM.
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Old 15th December 2017, 03:50 PM   #65
Mark Johnson is offline Mark Johnson  United States
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Crossover Distortion, the truth
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Originally Posted by scott wurcer View Post
BTW it's hard to make a general purpose amplifier (robust against difficult loads at any closed-loop gain) with output included compensation, but they do exist.
A lot of the discrete transistor opamps from your BurningAmp talk, had output included compensation. To be fair, none of them could deliver even 1 watt into an 8 ohm load. And I spoze they don't meet your "general purpose" requirement since the user had to change the values of the compensation components, to run at low closed-loop gain.

Last edited by Mark Johnson; 15th December 2017 at 03:53 PM. Reason: spoze
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Old 15th December 2017, 04:04 PM   #66
scott wurcer is offline scott wurcer  United States
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Quote:
Originally Posted by Mark Johnson View Post
A lot of the discrete transistor opamps from your BurningAmp talk, had output included compensation. To be fair, none of them could deliver even 1 watt into an 8 ohm load. And I spoze they don't meet your "general purpose" requirement since the user had to change the values of the compensation components, to run at low closed-loop gain.
I was referring to some IC op-amps with no external comp pins. There are a few but I forget which. The ADSL drivers don't count because that is a specific captive application and the design can include the recommended external circuit. The point is it includes the crossover inside the loop but the crossover is also responsible for output impedance modulation so reactive load drive becomes more of a problem (the fact that an EF looks inductive at high frequencies does not help either).
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Old 15th December 2017, 05:37 PM   #67
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Had built the undermost circuit. Inserted 2 mF at the output and driven any fullrange, > 90 dB;-)))

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Old 18th December 2017, 05:24 AM   #68
OnAudio is offline OnAudio
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The graphs on the effect of different levels of NFB are interesting
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Which are the not-true statements in Barney Oliver's treatise on Crossover Distortion? HP Journal, February 1971. Barney was the head of Hewlett Packard Laboratories.

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Old 18th December 2017, 05:30 AM   #69
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There are valid reasons on why we need GNFB

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