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Some Discussion on Amp EQs

Discussion in 'Amps and Cabs [BG]' started by dunwichamps, Jan 21, 2013.


  1. JimmyM

    JimmyM

    Apr 11, 2005
    Apopka, FL
    Endorsing: Yamaha, Ampeg, Line 6, EMG
    Ah, OK. For some reason that didn't pop out at me when I first read it, but it could have been that I'm extremely tired but can't sleep ;) Thanks Charlie.
     
  2. BassyBill

    BassyBill The smooth moderator... Gold Supporting Member

    Mar 12, 2005
    West Midlands UK
    I think post #1 in this thread is possibly the most epic opening post I have ever seen in any discussion on the forum.

    It's this sort of stuff that really makes TalkBass what it is. Thanks for taking the time and trouble to share this expert info.
     
  3. joelb79

    joelb79

    Mar 22, 2006
    Lansing, Michigan
    Incredible thread.
     
  4. arai

    arai Inactive

    Jul 16, 2007
    Really awesome thread. Thanks for sharing.
     
  5. One Drop

    One Drop

    Oct 10, 2004
    Swiss Alps
    This really makes my understanding of the different stacks much deeper and more easily related to how I practice using them. Wonderful and useful thread!

    The thought of a Hiwatt clone amp with a mid control like the SVT seems like it would make a holy grail combination. Has no one done this before?
     
  6. dunwichamps

    dunwichamps Commercial User

    Jul 23, 2012
    Owner: Dunwich Amps
    This is actually a good point. There are so many factors which control the overall system EQ (bass + pedals + amp + cab + room). Its entirely possible that given all these factors, that the sound coming out of the cab may not be perceived to be flat despite the controls being at noon.

    Given all these other factors I tried to be as consistent as possible and only do the preceding driver stage for each EQ. It would be very difficult to simulate beyond the phase inverters as the transformers are very complex and much harder to model accurately in LTSpice.
     
  7. dunwichamps

    dunwichamps Commercial User

    Jul 23, 2012
    Owner: Dunwich Amps
    thanks guys.

    I can add the Hiwatt Tone Stack from the 60s/70s which is sort of a highly tweaked FMV style eq.
     
  8. Mr. Foxen

    Mr. Foxen Commercial User

    Jul 24, 2009
    Bristol, UK
    Amp tinkerer at Ampstack
    Hiwatt one would be appreciated.
     
  9. dunwichamps

    dunwichamps Commercial User

    Jul 23, 2012
    Owner: Dunwich Amps
    No problemo. Probably be put up later tonight. About to hit work and wont be out for a while.
     
  10. JimmyM

    JimmyM

    Apr 11, 2005
    Apopka, FL
    Endorsing: Yamaha, Ampeg, Line 6, EMG
    Very good...thanks for the further explanation. And thanks for a really interesting discussion.
     
  11. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics

    Here's another nice discussion of these tone stacks from an old friend of mine, done back when ASCII diagrams were still uptown. Kind of the Cliffs Notes version of Nicks dissertation.
     
  12. father of fires

    father of fires Commercial User

    Nov 29, 2006
    BALTIMORE CITY
    Chief of Medicine at Damnation Audio
  13. dunwichamps

    dunwichamps Commercial User

    Jul 23, 2012
    Owner: Dunwich Amps
    That's the earliest hiwatt stack. The one I'm talking about was in the late 60s into the 70s

    See this scheme

    http://hiwatt.org/Schematics/DR_Pre4Input_v0a.gif

    Mhuss.com has pretty much all the info on hiwatts. Schemes, pics, history, everything.
     
  14. father of fires

    father of fires Commercial User

    Nov 29, 2006
    BALTIMORE CITY
    Chief of Medicine at Damnation Audio
    I played around with the one in the link a long time ago. I would say it was very "glassy" sounding. I've never heard the new ones.
     
  15. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    Yep, and you'd need to measure the transformers yourself in most cases too. You can find a few Fender guitar amp LTspice models online that attempt to model everything, including the speaker in an open-back cab in one case.

    Bass Gear Magazine posted SVT graphs that show frequency response at the output, both with controls at noon and also set to "nominal flat." It's well worth comparing those to the basic tone stack models.
     
  16. dunwichamps

    dunwichamps Commercial User

    Jul 23, 2012
    Owner: Dunwich Amps
    the one you linked is originally something from Sound City used on the earliest Hiwatts I believe

    See this scheme

    http://hiwatt.org/Schematics/SC105.gif

    By the time the late 60s rolled around they converted to a Bass Mids Treble stack closer to a FMV
     
  17. dunwichamps

    dunwichamps Commercial User

    Jul 23, 2012
    Owner: Dunwich Amps
    Of the OT Tap would give you even more info but then there is the cab. Probably easy to get a Ampeg fridge cab EQ but each cab is different.
     
  18. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    And then there's the room, of course. ;)
     
  19. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    These AB763 Twin Reverb sims (courtesy of the Yahoo Groups LTspice forum) include the power amp section and an output transformer model. I'm showing the curves both pre-phase inverter and post-output transformer, with a resistive dummy load.

    Normal Channel:

    [​IMG]

    [​IMG]

    Vibrato Channel:


    [​IMG]
     
  20. JimmyM

    JimmyM

    Apr 11, 2005
    Apopka, FL
    Endorsing: Yamaha, Ampeg, Line 6, EMG


    Here's a cool little video that advertises a line of A-Designs preamps but gets into a discussion about output transformers and the different tonal properties using different metals for them. Aimed at the layman, probably not quite as useful to the techies.
     
  21. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

     
    Apr 21, 2021

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