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why zero global negative feedback amplifier not observed in pass designs?
why zero global negative feedback amplifier not observed in pass designs?
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Old 19th September 2018, 06:49 PM   #1
rhythmsandy is offline rhythmsandy
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Default why zero global negative feedback amplifier not observed in pass designs?

many like no global negative feedback amplifiers and agreed super symmetry will eleminate much of the distortion.
In general many say no global feedback amps sound better but what is the reason behind why papa is not behind zero feedback amps?
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Old 19th September 2018, 06:54 PM   #2
jan.didden is offline jan.didden  Europe
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Why not ask him?

Jan
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Old 19th September 2018, 07:16 PM   #3
Nelson Pass is offline Nelson Pass  United States
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why zero global negative feedback amplifier not observed in pass designs?
You realize that I have numerous designs using ZGNFB, going back to
the Stasis amps at Threshold. At Pass Labs ZGNFB was applied to the
early X amplifiers - X1000, X600, X350. With the X250 we applied GNFB
and have used it in the X amplifiers since.

At First Watt, the F1, F2, M2, F4, SIT-1, SIT-2, and SIT-3 are all zero GNFB.
The other amplifiers have global feedback loops.

The decision to employ loop feedback around the output stage has always
been based on whether that particular amplifier sounded better that way.

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Old 19th September 2018, 08:21 PM   #4
WBS is offline WBS  United States
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why zero global negative feedback amplifier not observed in pass designs?
I'm still/always available as a subject for the evaluation of any new designs.

I'll be happy to provide the feedback!
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Old 19th September 2018, 08:29 PM   #5
Blk Dynamite is offline Blk Dynamite  United States
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I may be in the minority but I don't have a problem w feedback (global or local). Done judicially when a circuit is already low in distortion sounds fantastic. I don't hate if the circuit is well throughout
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Old 20th September 2018, 12:49 AM   #6
adason is offline adason  United States
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Quote:
Originally Posted by Nelson Pass View Post
You realize that I have numerous designs using ZGNFB, going back to
the Stasis amps at Threshold. At Pass Labs ZGNFB was applied to the
early X amplifiers - X1000, X600, X350. With the X250 we applied GNFB
and have used it in the X amplifiers since.

At First Watt, the F1, F2, M2, F4, SIT-1, SIT-2, and SIT-3 are all zero GNFB.
The other amplifiers have global feedback loops.

The decision to employ loop feedback around the output stage has always
been based on whether that particular amplifier sounded better that way.

I don't think he realize it. Otherwise he would not ask the master zero gnfb amplifiers such a question.
He typically starts the thread and then leaves...
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Old 20th September 2018, 08:03 AM   #7
wengtech is offline wengtech
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@rhythmsandy

do you know what is zero global negative feedback amplifier???
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Old 20th September 2018, 10:35 AM   #8
rhythmsandy is offline rhythmsandy
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Quote:
Originally Posted by wengtech View Post
@rhythmsandy

do you know what is zero global negative feedback amplifier???
I do understand local feedbacks and global feedback.
Yes I do know but I was in just a question that when it comes to super symmetry how is GNFB is not the primary parameter instead add two GNFB.
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Old 20th September 2018, 06:14 PM   #9
Nelson Pass is offline Nelson Pass  United States
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why zero global negative feedback amplifier not observed in pass designs?
Quote:
Originally Posted by adason View Post
I don't think he realize it. Otherwise he would not ask the master zero gnfb amplifiers such a question.
He typically starts the thread and then leaves...
Gives me a chance to toot my horn...
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Old 20th September 2018, 06:15 PM   #10
Nelson Pass is offline Nelson Pass  United States
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why zero global negative feedback amplifier not observed in pass designs?
Quote:
Originally Posted by rhythmsandy View Post
I do understand local feedbacks and global feedback.
Yes I do know but I was in just a question that when it comes to super symmetry how is GNFB is not the primary parameter instead add two GNFB.
Supersymmetry does not necessarily require GNFB. It does require a
symmetric pair of loops, but they don't have to be global.
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