Re: What can I expect by removing the NFB?

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In Reply to: What can I expect by removing the NFB? posted by Francis S on April 25, 2000 at 10:24:16:

Hi there,
>1. What can I expect sonically by removing the NFB circuit
>(this requires taking out 2 caps and a resistor/channel)?
More open Midrange, possibly less but more defined bass, more "thereness".
>2. Why is the NFB installed in the first place?
NFB has a "classic" valve sound and helps out substandard Output transformers for better measurements. In Japan the tendency is not as much towards Zero Negative Feedback and often Specifications count.
I would remove the negative feedback. On all Amplifers where I tried it I preferred the sound without negative feedback. I have found that to substantially improve either frequency response or distortion (substantially meaning 10db wrt distortion and 3db wrt frequency response) you need a lot of Negative feedback, at least 10 - 12db.
This means as much extra gain as that muct be present, meaning that you normally need two stages where usually one suffices. Ideally the amount of feedback applied would significantly exceed 20db, but such is difficult without risking all the (very audible) drawbacks of negative feedback audible in less than ideally implemented Solid State Amplifiers.
So basically, I prefer to do without negative Feedback as I can never enough spare gain to make it's use wortwhile. And certainly using only 3 - 6db Negative Feedback ALLWAYS made the circuit sound DRAMATICALLY worse, much more so than introducing a Cathode Follower or a SRRP into the Circuit.
My take, anyway. YMMV.
Later Thorsten

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Follow Ups Full Thread

Topic - What can I expect by removing the NFB? - Francis S 10:24:16 04/25/00 (6)

Re: What can I expect by removing the NFB? - Steven R. Rochlin 05:42:32 04/28/00 (0)

Re: What can I expect by removing the NFB? - Thorsten 10:39:06 04/25/00 (4)

Thanks! - Francis S 18:38:31 04/25/00 (0)

Re: What can I expect by removing the NFB? - GEO 11:42:51 04/25/00 (2)

Re: What can I expect by removing the NFB? - Thorsten 13:36:48 04/25/00 (1)

Re: What can I expect by removing the NFB? - GEO 19:07:13 04/25/00 (0)

Follow Ups

Re: What can I expect by removing the NFB? - Thorsten 10:39:06 04/25/00 (4)

Thanks! - Francis S 18:38:31 04/25/00 (0)

Re: What can I expect by removing the NFB? - GEO 11:42:51 04/25/00 (2)

Re: What can I expect by removing the NFB? - Thorsten 13:36:48 04/25/00 (1)

Re: What can I expect by removing the NFB? - GEO 19:07:13 04/25/00 (0)

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