1. We would like to remind our members that this is a privately owned, run and supported forum. You are here at the invitation and discretion of the owners. As such, rules and standards of conduct will be applied that help keep this forum functioning as the owners desire. These include, but are not limited to, removing content and even access to the forum.

    Please give yourself a refresher on the forum rules you agreed to follow when you signed up.
    Dismiss Notice

About Negative Feedback

Discussion in 'Tech Notes' started by FractalAudio, Jan 5, 2014.

  1. iaresee

    iaresee
    Expand Collapse
    Moderator
    Moderator

    Joined:
    Jul 1, 2009
    Messages:
    12,080
    Likes Received:
    11,640
    Location:
    Bay Area, CA
    There was a VW Beetle with a Fender badge on it that had an amp sim and a 1/4" jack on the dash board you could plug your guitar in to...
     
  2. 2112

    2112
    Expand Collapse
    Fractal Fanatic

    Joined:
    Jun 9, 2009
    Messages:
    2,606
    Likes Received:
    10,186
    Location:
    Perth, Western Australia
    *Axe-Fx Wishlist - VW/fender Model Plz*
     
    iaresee likes this.
  3. InsideOut

    InsideOut
    Expand Collapse
    Forum Addict

    Joined:
    May 3, 2009
    Messages:
    1,339
    Likes Received:
    614
    Location:
    SC, USA
    It will have to be 2 models - with and without proper emissions
     
    scottp and 2112 like this.
  4. Bman

    Bman
    Expand Collapse
    Veteran

    Joined:
    Dec 14, 2013
    Messages:
    636
    Likes Received:
    369
    Location:
    Houston, Texas
    I was unproductive at work today and scoured through this thread trying to understand Negative Feedback. And I think the 'aha' moment may have hit me not longer after Chris' 'aha' moment post a page or two back. I'd stumbled on using the parameter as a result of trying to tame some nuances that occur when I bump up an amp's input trim. I love the added gain that comes with the boost even with just a little boost. It sounds livelier to my ears than boosting with a pedal block. But the low end suffers, which is how I discovered the Neg. Feedback parameter. Boosting from it's default (1.5 I believe) on a Marshall amp block to between 2 or 3 smooths out the bad and feels like it takes another layer of blanket off the sound. It just sounds more pleasing on its own. But I did notice that when playing in a mix it cut less. Now after reading this, the way I understand it is this is because the EQ spectrum is widened out as you increase it. As Cliff sort of said: It becomes addictive and there is a trade-off. I liken it to a scooped EQ tone. Sounds awesome on its own but doesn't cut. It reminds me of when I was young and had a Crate 1x12 amp. I got a Heavy Metal Pedal and the thing sounded like all my hero's stacks.....until I added volume.

    Anywayt, the purpose of my post is to get some 'feedback' as to whether I'm correct about my conclusions. I suspect so, but need a sanity check. Then I can move on to solving the mix issue via EQ or Filter.
     
  5. yeky83

    yeky83
    Expand Collapse
    Veteran

    Joined:
    Sep 17, 2016
    Messages:
    891
    Likes Received:
    457
    Sounds like you have it backwards...? The part where Cliff says "addictive," he's referring to less negative feedback where the power amp response follows the speaker impedance curve with its scooped mids. If you increase the negative feedback, the speaker impedance has less of an effect on the response of the power amp, so the mids flatten out.
     
    Rex likes this.
  6. Bman

    Bman
    Expand Collapse
    Veteran

    Joined:
    Dec 14, 2013
    Messages:
    636
    Likes Received:
    369
    Location:
    Houston, Texas
    Ok. I think I may have presented it backwards but you've confirmed what I was trying to convey. Increasing it smooths out or broadens the frequency spectrum which in my case may have an unwanted result of smoothing out the boosted mids. More pleasing to the ears on it's own, but doesn't cut as well. Thanks, Yeky!
     
  7. Joe Bfstplk

    Joe Bfstplk
    Expand Collapse
    Regular

    Joined:
    May 7, 2019
    Messages:
    52
    Likes Received:
    40
    This forum channel's discussion reminds me of Ampage and the Weber VST boards, and even the old dial-up BBS that Ted ran back in the day. :)
     
  8. Handyman

    Handyman
    Expand Collapse
    Regular

    Joined:
    May 5, 2017
    Messages:
    73
    Likes Received:
    72
    Random factoid - the patent for negative feedback amplifiers was initially rejected as a perpetual motion machine in the US. It took years and years to get this sorted out with the USPTO.

    The patent went through without drama in Europe.

    Maybe there's a lesson here, but I'm not sure what it is.
     
    Joe Bfstplk likes this.
  9. shatteredsquare

    shatteredsquare
    Expand Collapse
    Forum Addict

    Joined:
    Nov 2, 2012
    Messages:
    1,174
    Likes Received:
    914
    I don't get it, the negative feedback is parasitic on the output, not additive...that's backwards from perpetual motion
     
    Joe Bfstplk likes this.
  10. Rex

    Rex
    Expand Collapse
    Legend!

    Joined:
    Jul 22, 2010
    Messages:
    19,953
    Likes Received:
    9,708
    From Merriam-Webster:

    factoid
    noun
    fac·toid | \ ˈfak-ˌtȯid \
    Definition of factoid


    1: an invented fact believed to be true because it appears in print
    2: a briefly stated and usually trivial fact



    Not sure which definition to go with here. :)
     
    shatteredsquare likes this.
  11. Joe Bfstplk

    Joe Bfstplk
    Expand Collapse
    Regular

    Joined:
    May 7, 2019
    Messages:
    52
    Likes Received:
    40
    The US Patent Office does strange things sometimes. Sometimes they check things very closely, other times it seems they are oblivious, and allow people to patent 'prior art'. Mesa has a fair number of things patented that really ought to have been rejected as prior art....
     

Share This Page